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Adenosine Deaminases Acting on RNA (ADARs) are members of a family of RNA editing enzymes that catalyze the conversion of adenosine into inosine in double-stranded RNA (dsRNA). ADARs' selective activity on dsRNA presents the ability to correct mutations at the transcriptome level using guiding oligonucleotides. However, this approach is limited by ADARs' preference for specific sequence contexts to achieve efficient editing. Substrates with a guanosine adjacent to the target adenosine in the 5' direction (5'-GA) are edited less efficiently compared to substrates with any other canonical nucleotides at this position. Previous studies showed that a G/purine mismatch at this position results in more efficient editing than a canonical G/C pair. Herein, we investigate a series of modified oligonucleotides containing purine or size-expanded nucleoside analogs on guide strands opposite the 5'-G (-1 position). The results demonstrate that modified adenosine and inosine analogs enhance editing at 5'-GA sites. Additionally, the inclusion of a size-expanded cytidine analog at this position improves editing over a control guide bearing cytidine. High-resolution crystal structures of ADAR:/RNA substrate complexes reveal the manner by which both inosine and size-expanded cytidine are capable of activating editing at 5'-GA sites. Further modification of these altered guide sequences for metabolic stability in human cells demonstrates that the incorporation of specific purine analogs at the -1 position significantly improves editing at 5'-GA sites.

A new emissive guanosine analog CF3thG, constructed by a single trifluoromethylation step from the previously reported thG, displays red-shifted absorption and emission spectra compared to its precursor. The impact of solvent type and polarity on the photophysical properties of CF3thG suggests that the electronic effects of the trifluoromethyl group dominate its behavior and demonstrates its susceptibility to microenvironmental polarity changes. In vitro transcription initiations using T7 RNA polymerase, initiated with CF3thG, result in highly emissive 5'-labeled RNA transcripts, demonstrating the tolerance of the enzyme toward the analog. Viability assays with HEK293T cells displayed no detrimental effects at tested concentrations, indicating the safety of the analog for cellular applications. Live cell imaging of the free emissive guanosine analog using confocal microscopy was facilitated by its red-shifted absorption and emission and adequate brightness. Real-time live cell imaging demonstrated the release of the guanosine analog from HEK293T cells at concentration-gradient conditions, which was suppressed by the addition of guanosine.

In order to develop a purine-reducing functional yak yoghurt, Lactobacillus paracasei 259 and commercial starter was used as the fermentation strain in this experiment. The inoculation amount of yak yoghurt strain was optimized by single factor experiment, and the quality changes of yak yoghurt during post-ripening period and storage period were observed. Gas chromatography-mass spectrometry (GC-MS) was used to analyze the changes of flavor substances during post-ripening period and storage period, and the purine-lowering activity of yak yoghurt was determined by high performance liquid chromatography (HPLC). The results showed that the post-ripening time of yak yoghurt was 24 h, the sensory score was the best when the inoculation amount of Lactobacillus paracasei 259 was 5%, the number of viable bacteria was 3.1x108 CFU/mL, the acidity was 96°T, and the inhibition rate of xanthine oxidase (XOD) was 51.51%. Yak yogurt with 5% inoculum of Lactobacillus paracasei 259 had a viable bacterial count higher than 107 CFU/mL during 28 d of storage, and the acidity was lower than 105.4°T. With the increase of storage time, the pH and water holding capacity decreased gradually, and the sensory quality, hardness, cohesion, viscosity, consistency and XOD inhibitory activity increased first and then decreased. The main flavor substances in yak yogurt after ripening were alcohols, esters, ketones, aromatic heterocycles and sulfur compounds. The acids increased at storage period compared to the post-ripening period. The relative content and quantity of alcohols were the highest, which gave the yogurt a fruity, floral and sweet flavor. The degradation of inosine and guanosine in yak yogurt during the storage period firstly increased and then decreased, up to 84.6% and 86.5%, respectively. It can be seen that yak yogurt fermented by Lactobacillus paracasei 259 is of better quality, inhibits xanthine oxidase activity, effectively degrades inosine guanosine, and has good potential for application in the prevention and adjunctive treatment of hyperuricemia. [ABSTRACT FROM AUTHOR]

Human mitochondrial tRNAs (mt-tRNAs), critical for mitochondrial biogenesis, are frequently associated with pathogenic mutations. These mt-tRNAs have unusual sequence motifs and require post-transcriptional modifications to stabilize their fragile structures. However, whether a modification that stabilizes a wild-type (WT) mt-tRNA would also stabilize its pathogenic variants is unknown. Here we show that the N1-methylation of guanosine at position 9 (m1G9) of mt-Leu(UAA), while stabilizing the WT tRNA, has a destabilizing effect on variants associated with MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes). This differential effect is further demonstrated, as removal of the m1G9 methylation, while damaging to the WT tRNA, is beneficial to the major pathogenic variant, improving the structure and activity of the variant. These results have therapeutic implications, suggesting that the N1-methylation of mt-tRNAs at position 9 is a determinant of pathogenicity and that controlling the methylation level is an important modulator of mt-tRNA-associated diseases. Here the authors show that the m1G9 post-transcriptional methylation differentially regulates the stability of the native and the MELAS variants of human mt-Leu(UAA) tRNA, contributing to mitochondrial pathology. [ABSTRACT FROM AUTHOR]

How eukaryotic ribosomes traverse messenger RNA (mRNA) leader sequences to search for protein-synthesis start sites remains one of the most mysterious aspects of translation and its regulation. While the search process is conventionally described by a linear "scanning" model, its exquisitely dynamic nature has restricted detailed mechanistic study. Here, we observed single Saccharomyces cerevisiae ribosomal scanning complexes in real time, finding that they scan diverse mRNA leaders at a rate of 10 to 20 nt s-1. We show that specific binding of a protein to its mRNA leader sequence substantially arrests scanning. Conversely, impairing scanning-complex guanosine 5'-triphosphate hydrolysis results in native start-site bypass. Our results illustrate an mRNA-centric, kinetically controlled regulatory model where the ribosomal pre-initiation complex amplifies a nuanced energetic landscape to regulate scanning and start-site selection fidelity. [ABSTRACT FROM AUTHOR]

Modification of guanosine to N7-methylguanosine (m7G) in the variable loop region of tRNA is catalyzed by the METTL1/WDR4 heterodimer and stabilizes target tRNA. Here, we reveal essential functions of Mettl1 in Drosophila fertility. Knockout of Mettl1 (Mettl1-KO) causes no major effect on the development of non-gonadal tissues, but abolishes the production of elongated spermatids and mature sperm, which is fully rescued by expression of a Mettl1-transgene, but not a catalytic-dead Mettl1 transgene. This demonstrates that Mettl1-dependent m7G is required for spermatogenesis. Mettl1-KO results in a loss of m7G modification on a subset of tRNAs and decreased tRNA abundance. Ribosome profiling shows that Mettl1-KO led to ribosomes stalling at codons decoded by tRNAs that were reduced in abundance. Mettl1-KO also significantly reduces the translation efficiency of genes involved in elongated spermatid formation and sperm stability. Germ cell-specific expression of Mettl1 rescues disrupted m7G tRNA modification and tRNA abundance in Mettl1-KO testes but not in non-gonadal tissues. Ribosome stalling is much less detectable in non-gonadal tissues than in Mettl1-KO testes. These findings reveal a developmental role for m7G tRNA modification and indicate that m7G modification-dependent tRNA abundance differs among tissues. Here the authors reveal essential functions of Mettl1, catalyzing N7-guanosine methylation (m7G) of tRNAs, in Drosophila male fertility through a regulation of the steady-state level of tRNAs and the translational efficiency of genes essential for spermatogenesis. [ABSTRACT FROM AUTHOR]

Copyright of Food Research & Development is the property of Food Research & Development Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Inhibitors of heterotrimeric G proteins are being developed as therapeutic agents. Epitomizing this approach are YM-254890 (YM) and FR900359 (FR), which are efficacious in models of thrombosis, hypertension, obesity, asthma, uveal melanoma, and pain, and under investigation as an FR-antibody conjugate in uveal melanoma clinical trials. YM/FR inhibits the Gq/11/14 subfamily by interfering with GDP (guanosine diphosphate) release, but by an unknown biophysical mechanism. Here, we show that YM inhibits GDP release by stabilizing closure between the Ras-like and α-helical domains of a Gα subunit. Nucleotide-free Gα adopts an ensemble of open and closed configurations, as indicated by single-molecule Förster resonance energy transfer and molecular dynamics simulations, whereas GDP and GTPγS (guanosine 5'-O-[gamma-thio]triphosphate) stabilize distinct closed configurations. YM stabilizes closure in the presence or absence of GDP without requiring an intact interdomain interface. All three classes of mammalian Gα subunits that are insensitive to YM/FR possess homologous but degenerate YM/FR binding sites, yet can be inhibited upon transplantation of the YM/FR binding site of Gq. Novel YM/FR analogs tailored to each class of G protein will provide powerful new tools for therapeutic investigation. [ABSTRACT FROM AUTHOR]

Halomonas bluephagenesis TD serves as an exceptional chassis for next generation industrial biotechnology to produce various products. However, the simultaneous editing of multiple loci in H. bluephagenesis TD remains a significant challenge. Herein, we report the development of a multiple loci genome editing system, named CRISPR-deaminase-assisted base editor (CRISPR-BE) in H. bluephagenesis TD. This system comprises two components: a cytidine (CRISPR-cBE) and an adenosine (CRISPR-aBE) deaminase-based base editor. CRISPR-cBE can introduce a cytidine to thymidine mutation with an efficiency of up to 100 % within a 7-nt editing window in H. bluephagenesis TD. Similarly, CRISPR-aBE demonstrates an efficiency of up to 100 % in converting adenosine to guanosine mutation within a 7-nt editing window. CRISPR-cBE has been further validated and successfully employed for simultaneous multiplexed editing in H. bluephagenesis TD. Our findings reveal that CRISPR-cBE efficiently inactivated all six copies of the IS1086 gene simultaneously by introducing stop codon. This system achieved an editing efficiency of 100 % and 41.67 % in inactivating two genes and three genes, respectively. By substituting the Pcas promoter with the inducible promoter PMmp1, we optimized CRISPR-cBE system and ultimately achieved 100 % editing efficiency in inactivating three genes. In conclusion, our research offers a robust and efficient method for concurrently modifying multiple loci in H. bluephagenesis TD, opening up vast possibilities for industrial applications in the future. [ABSTRACT FROM AUTHOR]

The second messenger guanosine 3',5'‐bis(diphosphate)/guanosine tetraphosphate (ppGpp) and guanosine 3'‐diphosphate 5'‐triphosphate/guanosine pentaphosphate (pppGpp) ((p)ppGpp) has been shown to be crucial for the survival of mycobacteria under hostile conditions. Unexpectedly, deletion of primary (p)ppGpp synthetase‐Rel did not completely diminish (p)ppGpp levels leading to the discovery of novel bifunctional enzyme‐RelZ, which displayed guanosine 5'‐monophosphate,3'‐diphosphate (pGpp), ppGpp, and pppGpp ((pp)pGpp) synthesis and RNAseHII activity. What conditions does it express itself under, and does it work in concert with Rel? The regulation of its transcription and whether the Rel enzyme plays a role in such regulation remain unclear. In this article, we have studied relZ promoter and compared its activity with rel promoter in different growth conditions. We observed that the promoter activity of relZ was constitutive; it is weaker than rel promoter, lies within 200 bp upstream of translation‐start site, and it increased under carbon starvation. Furthermore, the promoter activity of relZ was compromised in the rel‐knockout strain in the stationary phase. Our study unveils the dynamic regulation of relZ promoter activity by SigA and SigB sigma factors in different growth phases in mycobacteria. Importantly, elucidating the regulatory network of RelZ would enable the development of the targeted interventions for treating mycobacterial infections. [ABSTRACT FROM AUTHOR]

In order to develop a purine-reducing functional yak yoghurt, Lactobacillus paracasei 259 and commercial starter was used as the fermentation strain in this experiment. The inoculation amount of yak yoghurt strain was optimized by single factor experiment, and the quality changes of yak yoghurt during post-ripening period and storage period were observed. Gas chromatography-mass spectrometry (GC-MS) was used to analyze the changes of flavor substances during post-ripening period and storage period, and the purine-lowering activity of yak yoghurt was determined by high performance liquid chromatography (HPLC). The results showed that the post-ripening time of yak yoghurt was 24 h, the sensory score was the best when the inoculation amount of Lactobacillus paracasei 259 was 5%, the number of viable bacteria was 3.1×108 CFU/mL, the acidity was 96°T, and the inhibition rate of xanthine oxidase (XOD) was 51.51%. Yak yogurt with 5% inoculum of Lactobacillus paracasei 259 had a viable bacterial count higher than 107 CFU/mL during 28 d of storage, and the acidity was lower than 105.4°T. With the increase of storage time, the pH and water holding capacity decreased gradually, and the sensory quality, hardness, cohesion, viscosity, consistency and XOD inhibitory activity increased first and then decreased. The main flavor substances in yak yogurt after ripening were alcohols, esters, ketones, aromatic heterocycles and sulfur compounds. The acids increased at storage period compared to the post-ripening period. The relative content and quantity of alcohols were the highest, which gave the yogurt a fruity, floral and sweet flavor. The degradation of inosine and guanosine in yak yogurt during the storage period firstly increased and then decreased, up to 84.6% and 86.5%, respectively. It can be seen that yak yogurt fermented by Lactobacillus paracasei 259 is of better quality, inhibits xanthine oxidase activity, effectively degrades inosine guanosine, and has good potential for application in the prevention and adjunctive treatment of hyperuricemia.

Abstract Background Guanosine is a purine nucleoside that is widely used as a raw material for food additives and pharmaceutical products. Microbial fermentation is the main production method of guanosine. However, the guanosine-producing strains possess multiple metabolic pathway interactions and complex regulatory mechanisms. The lack of strains with efficiently producing-guanosine greatly limited industrial application. Results We attempted to efficiently produce guanosine in Escherichia coli using systematic metabolic engineering. First, we overexpressed the purine synthesis pathway from Bacillus subtilis and the prs gene, and deleted three genes involved in guanosine catabolism to increase guanosine accumulation. Subsequently, we attenuated purA expression and eliminated feedback and transcription dual inhibition. Then, we modified the metabolic flux of the glycolysis and Entner-Doudoroff (ED) pathways and performed redox cofactors rebalancing. Finally, transporter engineering and enhancing the guanosine synthesis pathway further increased the guanosine titre to 134.9 mg/L. After 72 h of the fed-batch fermentation in shake-flask, the guanosine titre achieved 289.8 mg/L. Conclusions Our results reveal that the guanosine synthesis pathway was successfully optimized by combinatorial metabolic engineering, which could be applicable to the efficient synthesis of other nucleoside products.

Abstract Background The gut microbiota plays a critical role in regulating brain function through the microbiome-gut-brain axis (MGBA). Dysbiosis of the gut microbiota is associated with neurological impairment in Traumatic brain injury (TBI) patients. Our previous study found that TBI results in a decrease in the abundance of Prevotella copri (P. copri). P. copri has been shown to have antioxidant effects in various diseases. Meanwhile, guanosine (GUO) is a metabolite of intestinal microbiota that can alleviate oxidative stress after TBI by activating the PI3K/Akt pathway. In this study, we investigated the effect of P. copri transplantation on TBI and its relationship with GUO-PI3K/Akt pathway. Methods In this study, a controlled cortical impact (CCI) model was used to induce TBI in adult male C57BL/6J mice. Subsequently, P. copri was transplanted by intragastric gavage for 7 consecutive days. To investigate the effect of the GUO-PI3K/Akt pathway in P. copri transplantation therapy, guanosine (GUO) was administered 2 h after TBI for 7 consecutive days, and PI3K inhibitor (LY294002) was administered 30 min before TBI. Various techniques were used to assess the effects of these interventions, including quantitative PCR, neurological behavior tests, metabolite analysis, ELISA, Western blot analysis, immunofluorescence, Evans blue assays, transmission electron microscopy, FITC-dextran permeability assay, gastrointestinal transit assessment, and 16 S rDNA sequencing. Results P. copri abundance was significantly reduced after TBI. P. copri transplantation alleviated motor and cognitive deficits tested by the NSS, Morris’s water maze and open field test. P. copri transplantation attenuated oxidative stress and blood-brain barrier damage and reduced neuronal apoptosis after TBI. In addition, P. copri transplantation resulted in the reshaping of the intestinal flora, improved gastrointestinal motility and intestinal permeability. Metabolomics and ELISA analysis revealed a significant increase in GUO levels in feces, serum and injured brain after P. copri transplantation. Furthermore, the expression of p-PI3K and p-Akt was found to be increased after P. copri transplantation and GUO treatment. Notably, PI3K inhibitor LY294002 treatment attenuated the observed improvements. Conclusions We demonstrate for the first time that P. copri transplantation can improve GI functions and alter gut microbiota dysbiosis after TBI. Additionally, P. copri transplantation can ameliorate neurological deficits, possibly via the GUO-PI3K/Akt signaling pathway after TBI.

The nucleoside guanosine is an endogenous neuromodulator associated with neuroprotection. The roles of guanosine during aging are still not fully elucidated. Guanosine modulates SUMOylation in neurons and astrocytes in vitro, but it is not known whether guanosine can modulate SUMOylation in vivo and improve cognitive functions during aging. SUMOylation is a post‐translational protein modification with potential neuroprotective roles. In this follow‐up study, we investigated whether guanosine could modulate SUMOylation in vivo and behavior in young and aged mice. Young (3‐month‐old) and aged (24‐month‐old) C57BL/6 mice were treated with guanosine (8 mg/kg intraperitoneal) daily for 14 days. Starting on day 8 of treatment, the following behavioral tests were performed: open field, novel object location, Y‐maze, sucrose splash test, and tail suspension test. Treatment with guanosine did not change the locomotor activity of young or aged mice in the open‐field test. Treatment with guanosine improved short‐term memory only for young mice but did not change the working memory of either young or aged mice, as evaluated using object recognition and the Y‐maze tests, respectively. Depressive‐like behaviors, such as impaired grooming evaluated through the splash test, did not change in either young or aged mice. However, young mice treated with guanosine increased their immobility time in the tail suspension test, suggesting an effect on behavioral coping strategies. Global SUMO1‐ylation was significantly increased in the hippocampus of young and aged mice after 14 days of treatment with guanosine, whereas no changes were detected in the cerebral cortex of either young or aged mice. Our findings demonstrate that guanosine also targets hippocampal SUMOylation in vivo, thereby contributing to a deeper understanding of its mechanisms of action. This highlights the involvement of SUMOylation in guanosine's modulatory and neuroprotective effects. [ABSTRACT FROM AUTHOR]

Aims/Introduction: Diabetic cardiomyopathy (DCM) is a prevalent condition among individuals with diabetes, and is associated with a high mortality rate. The anti‐oxidant properties of Jing Huang or Polygonatum sibiricum polysaccharide (PSP) have been extensively used to treat diabetes‐related disorders; however, its potential effectiveness against DCM remains unknown. This study aimed to investigate PSP's therapeutic effects on DCM in an experimental diabetic mouse model. Materials and Methods: To induce insulin resistance, mice were fed a high‐fat diet for 3 months, followed by intraperitoneal streptozotocin injection to induce slight hyperglycemia and develop DCM. Both DCM and control mice were given PSP orally for 3 weeks. Western blotting was used to detect the protein expressions of protein kinase G, C/EBP homologous protein, glucose‐regulated protein 78, phosphodiesterase type 5, protein kinase R‐like endoplasmic reticulum (ER) kinase, and phospho‐protein kinase R‐like endoplasmic reticulum kinase in heart tissue. Results: The results showed a reduction in bodyweight and blood glucose levels in the PSP therapy group compared with DCM group. PSP also improved cardiac function and had a negligible effect on malondialdehyde activity. Furthermore, the findings showed that PSP alleviated ER and oxidative stress observed in DCM mice hearts, leading to the inhibition of cyclic guanosine monophosphate‐specific phosphodiesterase type 5 and cardiac cyclic guanosine monophosphate reactivation. Phosphodiesterase type 5 inhibition reduced high‐fat diet‐induced cardiac dysfunction and decreased ER stress. Conclusions: PSP could effectively protect diabetic myocardium by inhibiting endoplasmic reticulum stress. These findings provide crucial insights into the potential of PSP to ameliorate DCM conditions in diabetic mice by decreasing ER and oxidative stress, and enhancing cyclic guanosine monophosphate protein kinase G signaling. [ABSTRACT FROM AUTHOR]

Copyright of Traditional Chinese Drug Research & Clinical Pharmacology is the property of Traditional Chinese Drug Research & Clinical Pharmacology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Chinese Institute of Food Science & Technology / Zhongguo Shipin Xuebao is the property of Journal of Chinese Institute of Food Science & Technology Periodical Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Guanosine is a purine nucleoside that is widely used as a raw material for food additives and pharmaceutical products. Microbial fermentation is the main production method of guanosine. However, the guanosine-producing strains possess multiple metabolic pathway interactions and complex regulatory mechanisms. The lack of strains with efficiently producing-guanosine greatly limited industrial application. Results: We attempted to efficiently produce guanosine in Escherichia coli using systematic metabolic engineering. First, we overexpressed the purine synthesis pathway from Bacillus subtilis and the prs gene, and deleted three genes involved in guanosine catabolism to increase guanosine accumulation. Subsequently, we attenuated purA expression and eliminated feedback and transcription dual inhibition. Then, we modified the metabolic flux of the glycolysis and Entner-Doudoroff (ED) pathways and performed redox cofactors rebalancing. Finally, transporter engineering and enhancing the guanosine synthesis pathway further increased the guanosine titre to 134.9 mg/L. After 72 h of the fed-batch fermentation in shake-flask, the guanosine titre achieved 289.8 mg/L. Conclusions: Our results reveal that the guanosine synthesis pathway was successfully optimized by combinatorial metabolic engineering, which could be applicable to the efficient synthesis of other nucleoside products. [ABSTRACT FROM AUTHOR]

Chloroplasts are the powerhouse of the plant cell, and their activity must be matched to plant growth to avoid photooxidative damage. We have identified a posttranslational mechanism linking the eukaryotic target of rapamycin (TOR) kinase that promotes growth and the guanosine tetraphosphate (ppGpp) signaling pathway of prokaryotic origins that regulates chloroplast activity and photosynthesis in particular. We find that RelA SpoT homolog 3 (RSH3), a nuclear-encoded enzyme responsible for ppGpp biosynthesis, interacts directly with the TOR complex via a plant-specific amino-terminal region which is phosphorylated in a TOR-dependent manner. Down-regulating TOR activity causes a rapid increase in ppGpp synthesis in RSH3 overexpressors and reduces photosynthetic capacity in an RSH-dependent manner in wild-type plants. The TOR-RSH3 signaling axis therefore regulates the equilibrium between chloroplast activity and plant growth, setting a precedent for the regulation of organellar function by TOR. [ABSTRACT FROM AUTHOR]

AbstractThe chemical synthesis of guanosine nucleosides generates both the N9 and N7 regioisomers, which require careful separation to obtain the desired N9 isomer. To preferentially obtain the N9 isomer, a bulky diphenylcarbamoyl (DPC) group can be installed at the O6 position of guanine. However, installation of the DPC group presents a challenging task due to low solubility of the N-acetyl protected guanine. Here we report the usage of commercially available 2-amino-6-chloro purine as a new strategy that offers a more efficient route to the synthesis of the guanine phosphoramidite of threose nucleic acid (TNA). [ABSTRACT FROM AUTHOR]

Monofunctional platinum complexes offer a promising alternative to cisplatin in cancer chemotherapy, showing a unique mechanism of action. Their ability to induce minor helix distortions effectively inhibits DNA transcription. In our study, we synthesized and characterized three monofunctional Pt(II) complexes with the general formula [Pt(en)(L)Cl]NO3, where en = ethylenediamine, and L = pyridine (py), 2-methylpyridine (2-mepy), and 2-phenylpyridine (2-phpy). The hydrolysis rates of [Pt(en)(py)Cl]NO3 (1) and [Pt(en)(2-mepy)Cl]NO3 (2) decrease with the bulkiness of the auxiliary ligand with k(1) = 2.28 ± 0.15 × 10−4 s−1 and k(2) = 8.69 ± 0.98 × 10−5 s−1 at 298 K. The complex [Pt(en)(2-phpy)Cl]Cl (3) demonstrated distinct behavior. Upon hydrolysis, an equilibrium (Keq = 0.385 mM) between the complexes [Pt(en)(2-phpy)Cl]+ and [Pt(en)(2-phpy-H+)]+ was observed with no evidence (NMR or HR-ESI-MS) for the presence of the aquated complex [Pt(en)(2-phpy)(H2O)]2+. Despite the kinetic similarities between phenanthriplatin and (2), complexes (1) and (2) exhibit minimal activity against A549 lung cancer cell line (IC50 > 100 μΜ), whereas complex (3) exhibits notable cytotoxicity (IC50 = 41.11 ± 2.1 μΜ). In examining the DNA binding of (1) and (2) to the DNA model guanosine (guo), we validated their binding through guoN7, which led to an increased population of the C3′-endo sugar conformation, as expected. However, we observed that the rapid transition 2E (C2′-endo) ↔ 3E (C3′-endo), in the case of [Pt(en)(py)(guo)](NO3)2 ([1-guo]), slows down in the case of [Pt(en)(2-mepy)(guo)](NO3)2 ([2-guo]), resulting in separate signals for the two conformers in the 1H NMR spectra. This phenomenon arises from the steric hindrance between the methyl group of pyridine and the sugar moiety of guanosine. Notably, this hindrance is absent in [2-(9-MeG)] (9-MeG = 9-methylguanine), probably due to the absence of a bulky sugar unit in 9-MeG. In the case of (3), where the bulkiness of the substitution on the pyridine is further increased by a phenyl group, we observed a notable proximity between 9-MeGH8 and the phenyl ring of 2-phpy. Considering that only (3) exhibited good cytotoxicity against the A549 cancer cell line, it is suggested that auxiliary ligands, L, with an extended aromatic system and proper orientation in complexes of the type cis-[Pt(en)(L)Cl]NO3, may enhance the cytotoxic activity of such complexes. [ABSTRACT FROM AUTHOR]

Background: The gut microbiota plays a critical role in regulating brain function through the microbiome-gut-brain axis (MGBA). Dysbiosis of the gut microbiota is associated with neurological impairment in Traumatic brain injury (TBI) patients. Our previous study found that TBI results in a decrease in the abundance of Prevotella copri (P. copri). P. copri has been shown to have antioxidant effects in various diseases. Meanwhile, guanosine (GUO) is a metabolite of intestinal microbiota that can alleviate oxidative stress after TBI by activating the PI3K/Akt pathway. In this study, we investigated the effect of P. copri transplantation on TBI and its relationship with GUO-PI3K/Akt pathway. Methods: In this study, a controlled cortical impact (CCI) model was used to induce TBI in adult male C57BL/6J mice. Subsequently, P. copri was transplanted by intragastric gavage for 7 consecutive days. To investigate the effect of the GUO-PI3K/Akt pathway in P. copri transplantation therapy, guanosine (GUO) was administered 2 h after TBI for 7 consecutive days, and PI3K inhibitor (LY294002) was administered 30 min before TBI. Various techniques were used to assess the effects of these interventions, including quantitative PCR, neurological behavior tests, metabolite analysis, ELISA, Western blot analysis, immunofluorescence, Evans blue assays, transmission electron microscopy, FITC-dextran permeability assay, gastrointestinal transit assessment, and 16 S rDNA sequencing. Results: P. copri abundance was significantly reduced after TBI. P. copri transplantation alleviated motor and cognitive deficits tested by the NSS, Morris's water maze and open field test. P. copri transplantation attenuated oxidative stress and blood-brain barrier damage and reduced neuronal apoptosis after TBI. In addition, P. copri transplantation resulted in the reshaping of the intestinal flora, improved gastrointestinal motility and intestinal permeability. Metabolomics and ELISA analysis revealed a significant increase in GUO levels in feces, serum and injured brain after P. copri transplantation. Furthermore, the expression of p-PI3K and p-Akt was found to be increased after P. copri transplantation and GUO treatment. Notably, PI3K inhibitor LY294002 treatment attenuated the observed improvements. Conclusions: We demonstrate for the first time that P. copri transplantation can improve GI functions and alter gut microbiota dysbiosis after TBI. Additionally, P. copri transplantation can ameliorate neurological deficits, possibly via the GUO-PI3K/Akt signaling pathway after TBI. [ABSTRACT FROM AUTHOR]

Background Bemnifosbuvir (AT-527) is a novel oral guanosine nucleotide antiviral drug for the treatment of persons with COVID-19. Direct assessment of drug disposition in the lungs, via bronchoalveolar lavage, is necessary to ensure antiviral drug levels at the primary site of SARS-CoV-2 infection are achieved. Objectives This Phase 1 study in healthy subjects aimed to assess the bronchopulmonary pharmacokinetics, safety and tolerability of repeated doses of bemnifosbuvir. Methods A total of 24 subjects were assigned to receive bemnifosbuvir twice daily at doses of 275, 550 or 825 mg for up to 3.5 days. Results AT-511, the free base of bemnifosbuvir, was largely eliminated from the plasma within 6 h post dose in all dosing groups. Antiviral drug levels of bemnifosbuvir were consistently achieved in the lungs with bemnifosbuvir 550 mg twice daily. The mean level of the guanosine nucleoside metabolite AT-273, the surrogate of the active triphosphate metabolite of the drug, measured in the epithelial lining fluid of the lungs was 0.62 µM at 4–5 h post dose. This exceeded the target in vitro 90% effective concentration (EC90) of 0.5 µM for antiviral drug exposure against SARS-CoV-2 replication in human airway epithelial cells. Bemnifosbuvir was well tolerated across all doses tested, and most treatment-emergent adverse events reported were mild in severity and resolved. Conclusions The favourable pharmacokinetics and safety profile of bemnifosbuvir demonstrates its potential as an oral antiviral treatment for COVID-19, with 550 mg bemnifosbuvir twice daily currently under further clinical evaluation in persons with COVID-19. [ABSTRACT FROM AUTHOR]

The in vivo codon decoding preferences of tRNAs with an authentic adenosine residue at position 34 of the anticodon, the wobble position, are largely unexplored because very few unmodified A34 tRNA genes exist across the three domains of life. The expanded wobble rules suggest that unmodified adenosine pairs most strongly with uracil, modestly with cytosine, and weakly with guanosine and adenosine. Inosine, a modified adenosine, on the other hand, pairs strongly with both uracil and cytosine and to a lesser extent adenosine. Orthogonal pair directed sense codon reassignment experiments offer a tool with which to interrogate the translational activity of A34 tRNAs because the introduced tRNA can be engineered with any anticodon. Our fluorescencebased screen utilizes the absolute requirement of tyrosine at position 66 of superfolder GFP for autocatalytic fluorophore formation. The introduced orthogonal tRNA competes with the endogenous translation machinery to incorporate tyrosine in response to a codon typically assigned another meaning in the genetic code. We evaluated the codon reassignment efficiencies of 15 of the 16 possible orthogonal tRNAs with A34 anticodons. We examined the Sanger sequencing chromatograms for cDNAs from each of the reverse transcribed tRNAs for evidence of inosine modification. Despite several A34 tRNAs decoding closely-related C-ending codons, partial inosine modification was detected for only three species. These experiments employ a single tRNA body with a single attached amino acid to interrogate the behavior of different anticodons in the background of in vivo E. coli translation and greatly expand the set of experimental measurements of the in vivo function of A34 tRNAs in translation. For the most part, unmodified A34 tRNAs largely pair with only U3 codons as the original wobble rules suggest. In instances with GC pairs in the first two codon positions, unmodified A34 tRNAs decode the C- and G-ending codons as well as the expected U-ending codon. These observations support the "two-out-of-three" and "strong and weak" codon hypotheses. [ABSTRACT FROM AUTHOR]

Background: Numerous metabolomic studies have confirmed the pivotal role of metabolic abnormalities in the development of idiopathic pulmonary fibrosis (IPF). Nevertheless, there is a lack of evidence on the causal relationship between circulating metabolites and the risk of IPF. Methods: The potential causality between 486 blood metabolites and IPF was determined through a bidirectional two-sample Mendelian randomization (TSMR) analysis. A genome-wide association study (GWAS) involving 7,824 participants was performed to analyze metabolite data, and a GWAS meta-analysis involving 6,257 IPF cases and 947,616 control European subjects was conducted to analyze IPF data. The TSMR analysis was performed primarily with the inverse variance weighted model, supplemented by weighted mode, MR-Egger regression, and weighted median estimators. A battery of sensitivity analyses was performed, including horizontal pleiotropy assessment, heterogeneity test, Steiger test, and leave-one-out analysis. Furthermore, replication analysis and meta-analysis were conducted with another GWAS dataset of IPF containing 4,125 IPF cases and 20,464 control subjects. Mediation analyses were used to identify the mediating role of confounders in the effect of metabolites on IPF. Results: There were four metabolites associated with the elevated risk of IPF, namely glucose (odds ratio [OR] = 2.49, 95% confidence interval [95%CI] = 1.13–5.49, P = 0.024), urea (OR = 6.24, 95% CI = 1.77–22.02, P = 0.004), guanosine (OR = 1.57, 95%CI = 1.07–2.30, P = 0.021), and ADpSGEGDFXAEGGGVR (OR = 1.70, 95%CI = 1.00–2.88, P = 0.0496). Of note, the effect of guanosine on IPF was found to be mediated by gastroesophageal reflux disease. Reverse Mendelian randomization analysis displayed that IPF might slightly elevate guanosine levels in the blood. Conclusion: Conclusively, hyperglycemia may confer a promoting effect on IPF, highlighting that attention should be paid to the relationship between diabetes and IPF, not solely to the diagnosis of diabetes. Additionally, urea, guanosine, and ADpSGEGDFXAEGGGVR also facilitate the development of IPF. This study may provide a reference for analyzing the potential mechanism of IPF and carry implications for the prevention and treatment of IPF. [ABSTRACT FROM AUTHOR]

This article discusses the development of a synthesis method for 3'-fluoro hexitol nucleic acids (FHNA) adenosine and guanosine phosphoramidites. The authors explain that antisense technology, which involves using oligonucleotides to downregulate gene expression, has shown promise in drug discovery. They describe the synthesis of FHNA pyrimidine nucleoside phosphoramidites and their properties, as well as the challenges faced in synthesizing FHNA purine nucleosides. The authors present two alternate routes for the synthesis of FHNA purine nucleosides and detail the steps involved in the synthesis process. They conclude that their synthetic method will facilitate the use of FHNA nucleic acids in genetic medicine and diagnostic applications. [Extracted from the article]

This article discusses the synthesis of α-l-threofuranosyl guanosine 3'-triphosphate (tGTP), which is an important building block for the construction of artificial genetic polymers. The traditional method for synthesizing tGTP involves a laborious and time-consuming process. However, the authors propose an alternative synthetic route using commercially available 6-chloropurine-2-amine, which simplifies the synthesis and reduces the use of hazardous solvents. The authors also compare two different methods for preparing tGTP nucleotides and conclude that the pyrene pyrophosphate approach is preferred due to its fewer synthetic steps. This improved approach could be advantageous for the large-scale synthesis of guanosine nucleosides. [Extracted from the article]

The G-quartet-like supramolecular assembly present in guanosine hydrogel templates macrocyclization between bis-azide and bis-alkyne fragments. The resulting macrocycle enhances viscoelastic properties, and strengthens the hydrogel network. This approach holds potential for the in situ synthesis of drugs and their simultaneous delivery in a stimuli-responsive manner. [ABSTRACT FROM AUTHOR]

Cyclic nucleotide binding domains (CNB) confer allosteric regulation by cAMP or cGMP to many signaling proteins, including PKA and PKG. PKA of phylogenetically distant Trypanosoma is the first exception as it is cyclic nucleotide-independent and responsive to nucleoside analogues (Bachmaier et al., 2019). Here, we show that natural nucleosides inosine, guanosine and adenosine are nanomolar affinity CNB ligands and activators of PKA orthologs of the important tropical pathogens Trypanosoma brucei, Trypanosoma cruzi, and Leishmania. The sequence and structural determinants of binding affinity, -specificity and kinase activation of PKAR were established by structure-activity relationship (SAR) analysis, co-crystal structures and mutagenesis. Substitution of two to three amino acids in the binding sites is sufficient for conversion of CNB domains from nucleoside to cyclic nucleotide specificity. In addition, a trypanosomatid-specific C-terminal helix (aD) is required for high affinity binding to CNB-B. The aD helix functions as a lid of the binding site that shields ligands from solvent. Selectivity of guanosine for CNB-B and of adenosine for CNB-A results in synergistic kinase activation at low nanomolar concentration. PKA pulldown from rapid lysis establishes guanosine as the predominant ligand in vivo in T. brucei bloodstream forms, whereas guanosine and adenosine seem to synergize in the procyclic developmental stage in the insect vector. We discuss the versatile use of CNB domains in evolution and recruitment of PKA for novel nucleoside-mediated signaling. [ABSTRACT FROM AUTHOR]

Translocation of transfer RNA (tRNA) and messenger RNA (mRNA) through the ribosome is catalyzed by the GTPase elongation factor G (EF-G) in bacteria. Although guanosine-5-triphosphate (GTP) hydrolysis accelerates translocation and is required for dissociation of EF-G, its fundamental role remains unclear. Here, we used ensemble Förster resonance energy transfer (FRET) to monitor how inhibition of GTP hydrolysis impacts the structural dynamics of the ribosome. We used FRET pairs S12-S19 and S11-S13, which unambiguously report on rotation of the 30S head domain, and the S6-L9 pair, which measures intersubunit rotation. Our results show that, in addition to slowing reverse intersubunit rotation, as shown previously, blocking GTP hydrolysis slows forward head rotation. Surprisingly, blocking GTP hydrolysis completely abolishes reverse head rotation. We find that the S13-L33 FRET pair, which has been used in previous studies to monitor head rotation, appears to report almost exclusively on intersubunit rotation. Furthermore, we find that the signal from quenching of 3-terminal pyrene-labeled mRNA, which is used extensively to follow mRNA translocation, correlates most closely with reverse intersubunit rotation. To account for our finding that blocking GTP hydrolysis abolishes a rotational event that occurs after the movements of mRNA and tRNAs are essentially complete, we propose that the primary role of GTP hydrolysis is to create an irreversible step in a mechanism that prevents release of EF-G until both the tRNAs and mRNA have moved by one full codon, ensuring productive translocation and maintenance of the translational reading frame.

ADARs (adenosine deaminases acting on RNA) can be directed to sites in the transcriptome by complementary guide strands allowing for the correction of disease-causing mutations at the RNA level. However, ADARs show bias against editing adenosines with a guanosine 5' nearest neighbor (5'-GA sites), limiting the scope of this approach. Earlier studies suggested this effect arises from a clash in the RNA minor groove involving the 2-amino group of the guanosine adjacent to an editing site. Here we show that nucleosides capable of pairing with guanosine in a syn conformation enhance editing for 5'-GA sites. We describe the crystal structure of a fragment of human ADAR2 bound to RNA bearing a G:G pair adjacent to an editing site. The two guanosines form a Gsyn:Ganti pair solving the steric problem by flipping the 2-amino group of the guanosine adjacent to the editing site into the major groove. Also, duplexes with 2'-deoxyadenosine and 3-deaza-2'-deoxyadenosine displayed increased editing efficiency, suggesting the formation of a Gsyn:AH+anti pair. This was supported by X-ray crystallography of an ADAR complex with RNA bearing a G:3-deaza dA pair. This study shows how non-Watson-Crick pairing in duplex RNA can facilitate ADAR editing enabling the design of next generation guide strands for therapeutic RNA editing.

Codon usage of each genome is closely correlated with the abundance of tRNA isoacceptors. How codon usage bias is resolved by tRNA post-transcriptional modifications is largely unknown. Here we demonstrate that the N1-methylation of guanosine at position 37 (m1G37) on the 3-side of the anticodon, while not directly responsible for reading of codons, is a neutralizer that resolves differential decoding of proline codons. A genome-wide suppressor screen of a non-viable Escherichia coli strain, lacking m1G37, identifies proS suppressor mutations, indicating a coupling of methylation with tRNA prolyl-aminoacylation that sets the limit of cell viability. Using these suppressors, where prolyl-aminoacylation is decoupled from tRNA methylation, we show that m1G37 neutralizes differential translation of proline codons by the major isoacceptor. Lack of m1G37 inactivates this neutralization and exposes the need for a minor isoacceptor for cell viability. This work has medical implications for bacterial species that exclusively use the major isoacceptor for survival.

We used in vitro selection to identify DNAzymes that acylate the exocyclic nucleobase amines of cytidine, guanosine, and adenosine in DNA oligonucleotides. The acyl donor was the 2,3,5,6‐tetrafluorophenyl ester (TFPE) of a 5′‐carboxyl oligonucleotide. Yields are as high as >95 % in 6 h. Several of the N‐acylation DNAzymes are catalytically active with RNA rather than DNA oligonucleotide substrates, and eight of nine DNAzymes for modifying C are site‐specific (>95 %) for one particular substrate nucleotide. These findings expand the catalytic ability of DNA to include site‐specific N‐acylation of oligonucleotide nucleobases. Future efforts will investigate the DNA and RNA substrate sequence generality of DNAzymes for oligonucleotide nucleobase N‐acylation, toward a universal approach for site‐specific oligonucleotide modification. [ABSTRACT FROM AUTHOR]

Homopurine strands are known to form antiparallel triplexes stabilized by G*G and A*A Hoogsteen pairs, which have two hydrogen bonds. But there has been no report on the parallel triplex formation of homopurine involving both adenosine and guanosine to the duplex. In this paper, we first report parallel triplex formation between a homopurine serinol nucleic acid (SNA) strand and an RNA/SNA duplex. Melting profiles revealed that the parallel SNA:RNA*SNA triplex was remarkably stable, even though the A*A pair has a single hydrogen bond. An L -acyclic threoninol nucleic acid (L -aTNA) homopurine strand also formed a stable parallel triplex with an L -aTNA/RNA duplex. [ABSTRACT FROM AUTHOR]

Objective: A new approach to the synthesis of the cap structure analogue with the correct orientation (Anti-Reverse Cap Analog, ARCA) having a classical structure (dimethylated guanosine dinucleotide 2mGpppG) is proposed. The traditional approach to its preparation is the condensation of activated 7,3′-O-dimethylguanosine-5′diphosphate with guanosine-5′-monophosphate. We suggest to use 3′-O-methylguanosine only for the synthesis of dimethylated guanosine-5′-monophosphate, and to introduce the activated guanosine-5′-diphosphate into the condensation. Methods: Conditions for phosphorylation of 3′-O-methylguanosine were determined to avoid the formation of by-product 3′-O-methyl-5′-deoxy-5′-chloroguanosine-2′-phosphate. Results and Discussion: At the last step of the synthesis, we used activated guanosine-5′-diphosphate (IV) and 7,3′-O-dimethylguanosine-5′monophosphate (VI). Compound (IV) was prepared by a three-step synthesis starting with guanosine. Compound (VI) was prepared by a two-step synthesis starting with 3′-O-methylguanosine. During phosphorylation of 3′-Omethylguanosine an unexpected compound (3′-O-methyl-5′-deoxy-5′-chloroguanosine-2′-phosphate) was formed. The structure of this compound was confirmed by NMR and mass-spectroscopy data. Conclusions: A new approach to the synthesis of ARCA of the guanosine type, methylated at the N7 and 3′ positions of guanosine was proposed. A scheme for the condensation of 7,3′-O-dimethylguanosine-5′-monophosphate and guanosine-5′-diphosphate was implemented. Guanosine 5′-diphosphate was used as activated component. Conditions for phosphorylation of 3′-Omethylguanosine were determined to avoid the formation of by-product 3′-O-methyl-5′-deoxy-5′-chloroguanosine2′-phosphate. ARCA was synthesized in high yield (89% at condensation step). The suggested version of the ARCA synthesis can be easily scaled. [ABSTRACT FROM AUTHOR]

A synthesis route of a novel phosphoramide morpholinoline-oligoguanylate monomer using guanosine as raw material was developed.Based on the protection of the amino group on the base and 5’-OH in ribose, the ribose ring is converted into a morpholine ring to obtain the protected morpholine guanosine.A triphenylmethylation reaction was carried out on the morpholine ring and purine 6-O position was modified using the Mitsunobu reaction.N,N-dimethylaminophosphorylation reaction is performed on the deprotected hydroxyl group to synthesize the target product.In this study, the conditions of the Mitsunobu reaction and phosphorylation reaction were optimized.Under optimized conditions, the total yield of the new synthetic route was 14.1%.The structure of intermediate products and target products were characterized by LC-MS, ¹H NMR and 31P NMR. [ABSTRACT FROM AUTHOR]

Protein synthesis is important and regulated by various mechanisms in the cell. Translation initiation in eukaryotes starts at the 5′ cap and is the most complex of the three phases of mRNA translation. It requires methylation of the N7 position of the terminal guanosine (m7G). The canonical capping occurs in the nucleus, however, cytoplasmic recapping has been discovered. It functions in switching mRNAs between translating and non‐translating states, but the individual steps are difficult to dissect. We targeted cytoplasmic cap methylation as the ultimate step of cytoplasmic recapping. We present an N7G photocaged 5′ cap that can be activated for cytoplasmic methylation by visible light. We report chemical and chemo‐enzymatic synthesis of this 5′ cap with 7‐(diethylamino)‐4‐methyl‐coumarin (DEACM) at the N7G and validate that it is not bound by translation initiation factor 4E (eIF4E). We demonstrate incorporation into mRNA, the release of unmethylated cap analog and enzymatic remethylation to functional cap 0 after irradiation at 450 nm. In cells, irradiation triggers translation of mRNAs with the N7G photocaged 5′ cap via cytoplasmic cap methylation. [ABSTRACT FROM AUTHOR]

Nucleoside monophosphates perform various essential functions and serve as second messengers in living systems. Despite the success of nucleotide‐selective probes based on proteins, the creation of synthetic receptors for nucleoside monophosphates remains a challenging task. In this paper, we explore the design of synthetic receptors based on a combination of three recognition motifs. We show that each binding motif contributes to the formation of the host‐guest complexes. The core macrocycle provides recognition of the phosphate residue of the nucleotide, while naphthalimide and the attached cytosine residue participate in the coordination of the nucleobase via π‐π and hydrogen bonding interactions. The presence of cytosine in the receptor structure substantially increases the overall affinity of receptors for nucleotides. A considerable increase (100‐fold) in binding affinities is observed for the tetranucleotide DNA sequences 5′‐GGGG ‐3′ and 5′‐CCCC‐3′, as compared to the previously reported system without the attached cytosine. [ABSTRACT FROM AUTHOR]

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer with poor prognosis. TNBCs with high homologous recombination deficiency (HRD) scores benefit from DNA-damaging agents, including platinum drugs and poly(ADP-ribose) polymerase (PARP) inhibitors, whereas those with low HRD scores still lack therapeutic options. Therefore, we sought to exploit metabolic alterations to induce HRD and sensitize DNA-damaging agents in TNBCs with low HRD scores. We systematically analyzed TNBC metabolomics and identified a metabolite, guanosine diphosphate (GDP)–mannose (GDP-M), that impeded homologous recombination repair (HRR). Mechanistically, the low expression of the upstream enzyme GDP-mannose-pyrophosphorylase-A (GMPPA) led to the endogenous up-regulation of GDP-M in TNBC. The accumulation of GDP-M in tumor cells further reduced the interaction between breast cancer susceptibility gene 2 (BRCA2) and ubiquitin-specific peptidase 21 (USP21), which promoted the ubiquitin-mediated degradation of BRCA2 to inhibit HRR. Therapeutically, we illustrated that the supplementation of GDP-M sensitized DNA-damaging agents to impair tumor growth in both in vitro (cancer cell line and patient-derived organoid) and in vivo (xenograft in immunodeficient mouse) models. Moreover, the combination of GDP-M with DNA-damaging agents activated STING-dependent antitumor immunity in immunocompetent syngeneic mouse models. Therefore, GDP-M supplementation combined with PARP inhibition augmented the efficacy of anti–PD-1 antibodies. Together, these findings suggest that GDP-M is a crucial HRD-related metabolite and propose a promising therapeutic strategy for TNBCs with low HRD scores using the combination of GDP-M, PARP inhibitors, and anti–PD-1 immunotherapy. Editor's summary: Triple-negative breast cancer (TNBC) has worse prognosis than other breast cancer subtypes, and metabolites have been suggested as a potential target for therapy. Here, Ding et al. evaluated metabolites associated with homologous recombination deficiency in TNBC and identified that guanosine diphosphate–mannose (GDP-M) could suppress DNA repair and could be combined with other DNA repair–targeted therapy. They evaluated the combination of GDP-M with PARP inhibition and anti–PD-1 therapy to enhance antitumor immunity and survival of mouse models. This demonstrates the promising effects of GDP-M supplementation for TNBC therapy that requires further study. —Dorothy Hallberg [ABSTRACT FROM AUTHOR]

Breynia vitis-idaea (Phyllanthaceae) is used in the Chinese traditional medicinal system, to treat chronic lung disease and wound healing. This study was aimed to identify the chemical constituents of B. vitis-idaea having biological properties by in-vitro and in-silico methods. Breynia vitis-idaea leaf extract was screened for the presence of phenol, flavonoid contents, antibacterial, antioxidant, and antidiabetic activities. Molecular docking of secondary metabolites with target proteins and ADMET analysis was done. Preliminary phytochemical screening of B. vitis-idaea contains a variety of phytoconstituents such as alkaloids, flavonoids, carbohydrates, tannin, saponin, terpenoids, phenol, protein, steroids and glycosides. The antibacterial activity of methanol leaf extract of B. vitis-idaea evaluated against Escherichia coli (17 mm), Klebsiella pneumoniae (16 mm), Bacillus subtilis (22 mm), and Staphylococcus aureus (18 mm) showed high activity. Antioxidant activities were assessed by ABTS and FRAP assays and their IC 50 values were 41.06 µg/mL and 46.40 µL/mL, respectively. α-amylase and α-glucosidase activity showed IC 50 values of 20.42 µg/mL and 14.60 µg/mL, respectively. Molecular docking study showed strong binding activity of γ-sitosterol to α-amylase and α-glucosidase, followed by guanosine and arbutin. ADMET analysis shows that γ-sitosterol, guanosine, and arbutin are good drug candidates. This work demonstrates the anti-diabetic potential of B. vitis-idaea. [Display omitted] • GC-MS study of B. vitis-idaea reveals 21 secondary metabolites • Three major compounds were identified (γ-sitosterol, guanosine and arbutin) • Strong binding affinity to α-amylase and α-glucosidase observed [ABSTRACT FROM AUTHOR]

The cyanobacterium Synechococcus elongatus PCC 7942 accumulates alarmone guanosine tetraphosphate (ppGpp) under stress conditions, such as darkness. A previous study observed that artificial ppGpp accumulation under photosynthetic conditions led to the downregulation of genes involved in the nitrogen assimilation system, which is activated by the global nitrogen regulator NtcA, suggesting that ppGpp regulates NtcA activity. However, the details of this mechanism have not been elucidated. Here, we investigate the metabolic responses associated with ppGpp accumulation by heterologous expression of the ppGpp synthetase RelQ. The pool size of 2-oxoglutarate (2-OG), which activates NtcA, is significantly decreased upon ppGpp accumulation. De novo 13C-labeled CO2 assimilation into the Calvin-Benson-Bassham cycle and glycolytic intermediates continues irrespective of ppGpp accumulation, whereas the labeling of 2-OG is significantly decreased under ppGpp accumulation. The low 2-OG levels in the RelQ overexpression cells could be because of the inhibition of metabolic enzymes, including aconitase, which are responsible for 2-OG biosynthesis. We propose a metabolic rearrangement by ppGpp accumulation, which negatively regulates 2-OG levels to maintain carbon and nitrogen balance. Elevated levels of alarmone guanosine tetraphosphate (ppGpp) in the cyanobacterium Synechococcus elongatus reduce de novo synthesis of 2-oxoglutarate, potentially by inhibiting metabolic enzymes like aconitase. [ABSTRACT FROM AUTHOR]

Metallo-base pairs are of immense interest. However, uncertainties remain regarding Ag+–nucleic acid component interactions. Instead of a coordinated polymer [C–Ag][NO3] (1) embedded with Ag+ nanowires in an aqueous C/AgNO3 system, a novel base paired ionic crystal CH+–NO3− (2) was formed in a complex hydrogel system comprising guanosine (G), cytidine (C) and AgNO3. The static structural characteristics and underlying coupled reaction mechanisms driving the proton transfer between the G and C in this multi-component system were characterized. This information will be valuable in the context of bio-inorganic chemistry involving G- and C-rich genomic sequences. [ABSTRACT FROM AUTHOR]

Experimental studies of the degradation of two ribonucleosides (guanosine and uridine) were carried out by making use of mechanochemistry. Mechanochemical experiments reveal the decomposition of guanosine and uridine, promoted by nickel(II) and carbonate ions, into guanine and uracil, respectively. These nucleobases were identified by HPLC and 1H NMR spectroscopy (this applied only to uracil). Additionally, density-functional theory (DFT) methodologies were used to probe the energetic viability of several degradation pathways, including in the presence of the abovementioned ions. Three mechanisms were analysed via ribose ring-opening: dry, single-molecule water-assisted, and metal-assisted, wherein the last two mechanisms confirmed the mechanochemical degradation of both ribonucleosides into respective nucleobase moieties. These results can contribute to an astrobiological interpretation of the extraterrestrial sample's contents. [ABSTRACT FROM AUTHOR]

Guanosine pentaphosphate and guanosine tetraphosphate are collectively called (p)ppGpp (Guanosine tetraphosphate and pentaphosphate). (p)ppGpp content in plants is affected by conditions such as light, salt, pH, UV light, and environmental phytohormones. The synthesis and hydrolysis of (p)ppGpp in plants is accomplished by a class of proteins called RSH (RelA/SpoT homologs). To date, a systematic and comprehensive genome-wide analysis of the RSH gene family in wheat and its closely related species has not been conducted. In this study, 15, 14, 12, and 8 members of RSH were identified in wheat (Triticum aestivum), Triticum dicoccoides, Triticum urartu and Aegilops tauschii respectively. Based on the conserved structural domains of the RSH genes, the TaRSHs have been categorized into TaRSH and TaCRSH. The gene duplications in the TaRSH gene family were all identified as segmental duplications indicating that the TaRSH family plays a significant role in expansion and that segmental duplications maintain a degree of genetic stability. Through the analysis of transcriptome data and RT-qPCR experiments, it was observed that the expression levels of TaRSHs were upregulated in response to abiotic stress. This upregulation suggests that TaRSHs play a crucial role in enhancing the resilience of wheat to adverse environmental conditions during its growth and development. Their increased expression likely contributes to the acquisition of stress tolerance mechanisms in wheat. Especially under NaCl stress, the expression levels increased most significantly. The more detailed systematic analysis provided in this article will help us understand the role of TaRSHs and provide a reference for further research on its molecular biological functions in wheat. [ABSTRACT FROM AUTHOR]

BACKGROUND: As the important building blocks of nucleic acids, purines are alkaloids and responsible for hyperuricemia and gout. The purine content in Huangjiu is higher, and mainly exists in the form of free bases, which is easier to be absorbed by human body. However, the currently available reports on purine in Huangjiu mainly focus on detection methods and content survey. No studies on the regulation of the purine content in Huangjiu have been reported. RESULTS: Eighty‐four strains, with the degradation capacity of purine, were screened from the fermentation broth of Huangjiu. In detail, the isolated lactic acid bacteria (LAB) strain 75 # showed the strongest degradation ability of guanosine, inosine and four purines, which reduce their levels by 83.4% (guanosine), 97.4% (inosine), 95.1% (adenine), 95.0% (guanine), 94.9% (hypoxanthine) and 65.9% (xanthine), respectively. Subsequently, the LAB strain 75# was identified to be Limosilactobacillus fermentum by 16S rRNA gene sequencing, which was named as Limosilactobacillus fermentum LF‐1 and applied to the fermentation of Huangjiu in the laboratory. Compared with the fermentation broth of Huangjiu without adding L. fermentum LF‐1, the content of purine compounds in the fermentation broth inoculated with L. fermentum LF‐1 was reduced by 64.7%. In addition, the fermented Huangjiu had richer flavor compounds, and the physicochemical indices were in accordance with the national standard of Chinese Huangjiu. CONCLUSION: The screened strain L. fermentum LF‐1 may be a promising probiotic for the development of a novel that can efficiently degrade purine in Huangjiu. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

In contribution to the pharmaceutical development of cyclic guanosine monophosphorothioate analogue cGMPSA as a potential active pharmaceutical ingredient (API) for the treatment of inherited retinal degenerations (IRDs), its neutral form (cGMPSA‐H) and salts of sodium (‐Na), calcium (‐Ca), ammonium (‐NH4), triethylammonium (‐TEA), tris(hydroxymethyl)aminomethane (‐Tris), benethamine (‐Bnet), and benzathine (‐BZ) were prepared. Their solid‐state properties were studied with differential scanning calorimetry, thermogravimetric analysis, hot‐stage microscopy, and dynamic vapor sorption, and their solubilities were measured in deionized H2O as well as aqueous HCl and NaOH buffers. A total of 21 crystal modifications of cGMPSA were found and characterized by X‐ray powder diffraction. Despite their crystalline character, no API forms featured any observable melting points during thermal analyses and instead underwent exothermic decomposition at ≥163 °C. Both the vapor sorption behavior and solubility were found to differ significantly across the API forms. cGMPSA‐BZ featured the lowest aqueous solubility and hygroscopicity, with 50 μg/mL and 5 % mass gain at maximum relative humidity. The synthesis and crystallization of some crystal modifications were upscaled to >10 g. Single crystal X‐ray diffraction was performed which resulted in the first crystal structure determination and absolute configuration of a cyclic guanosine monophosphorothioate, confirming the RP‐ conformation at the phosphorus atom. [ABSTRACT FROM AUTHOR]

Virtually all bacterial species synthesize (p)ppGpp (guanosine penta- or tetraphosphate), a pleiotropic regulator of the so-called stringent response, which controls many aspects of cellular physiology and metabolism. In Escherichia coli, (p) ppGpp levels are controlled by two homologous enzymes: the (p)ppGpp synthetase RelA and the bifunctional synthetase/hydrolase SpoT. We recently identified several protein candidates that can modulate (p)ppGpp levels in E. coli. In this work, we show that the putative two-component system connector protein YmgB can promote SpoT-dependent accumulation of ppGpp in E. coli. Importantly, we determined that the control of SpoT activities by YmgB is independent of its proposed role in the two-component Rcs system, and these two functions can be uncoupled. Using genetic and structure-function analysis, we show that the regulation of SpoT activities by YmgB occurs by functional and direct binding in vivo and in vitro to the TGS and Helical domains of SpoT. These results further support the role of these domains in controlling the reciprocal enzymatic states. [ABSTRACT FROM AUTHOR]

Guanosine is often used to construct supramolecular hydrogels due to its self-assembly properties, however, the high temperature and strong alkaline construction methods greatly limit its application in biomedical fields. In this work, a guanosine-driven hyaluronic acid-based supramolecular hydrogel was developed under mild condition by employing phenylboronic acid-functionalized hyaluronic acid (HA-PBA) backbone and guanosine molecules. Guanosines self-assembled into G-quartet planes under potassium ion conditions, and formed boronic ester bonds with HA-PBA, which induced rapid formation of dynamically cross-linked hydrogels. Hemin was then binding to the G-quartet plane via π-π interactions in the hydrogels, which exhibited peroxidase activity and were highly effective in killing bacteria by generating hydroxyl radicals in the presence of H 2 O 2. Furthermore, glucose oxidase (GOx) was incorporated into the hydrogels and the HP/G@hemin@GOx hydrogels showed good antibacterial properties, modulation of wound glucose and ROS level, and good therapeutic efficacy for diabetic chronic wounds. Overall, the self-assembly of guanosine has been shown for the first time to be a feasible method for constructing natural polymer-based supramolecular hydrogels. This guanosine-driven HA-based supramolecular hydrogel can act as a potential wound dressing for chronic diabetic wound treatment. Chronic wound repair remains an unsolved clinical challenge. Herein, we propose to utilize phenylboronic acid-modified hyaluronic acid and guanosine to construct supramolecular gels with peroxidase activity for chronic wound treatment. The self-assembly behavior of guanosine drives the natural macromolecular backbone to form the hydrogel, and the proposed method simplifies the gelation conditions and improves its biosafety. The G-quartets formed by the self-assembly of guanosine can act as the loading site for hemin. G-quartet/hemin complex imported peroxidase activity to the hydrogels, endowing them with the ability to kill bacteria and regulate ROS levels of cells in the wound site. This guanosine-driven supramolecular hydrogel significantly increased the rate of wound healing in diabetic mice, promising a new strategy for chronic wound treatment. [Display omitted] [ABSTRACT FROM AUTHOR]