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Background Heat shock transcription factor1 (HSF1) was overexpressed to promote glutaminolysis and activate mTOR in colorectal cancer (CRC). Here, we investigated the mechanism for cancer-specific overexpression of HSF1. Methods HSF1 expression was analyzed by chromatin immunoprecipitation, qRT-PCR, immunohistochemistry staining and immunoblotting. HSF1 translation was explored by polysome profiling and nascent protein analysis. Biotin pulldown and m6A RNA immunoprecipitation were applied to investigate RNA/RNA interaction and m6A modification. The relevance of HSF1 to CRC was analyzed in APCmin/+ and APCmin/+ HSF1+/−mice. Results HSF1 expression and activity were reduced after the inhibition of WNT/β-catenin signaling by pyrvinium or β-catenin knockdown, but elevated upon its activation by lithium chloride (LiCl) or β-catenin overexpression. There are much less upregulated genes in HSF1-KO MEF treated with LiCl when compared with LiCl-treated WT MEF. HSF1 protein expression was positively correlated with β-catenin expression in cell lines and primary tissues. After β-catenin depletion, HSF1 mRNA translation was impaired, accompanied by the reduction of its m6A modification and the upregulation of miR455-3p, which can interact with 3′-UTR of HSF1 mRNA to repress its translation. Interestingly, inhibition of miR455-3p rescued β-catenin depletion-induced reduction of HSF1 m6A modification and METTL3 interaction. Both the size and number of tumors were significantly reduced in APCmin/+ mice when HSF1 was genetically knocked-out or chemically inhibited. Conclusions β-catenin suppresses miR455-3p generation to stimulate m6A modification and subsequent translation of HSF1 mRNA. HSF1 is important for β-catenin to promote CRC development. Targeting HSF1 could be a potential strategy for the intervention of β-catenin-driven cancers.

Metabolic reprogramming is a hallmark of cancer. Mammalian genome is characterized by pervasive transcription, generating abundant non-coding RNAs (ncRNAs). Long non-coding RNAs (lncRNAs) are freshly discovered functional ncRNAs exerting extensive regulatory impact through diverse mechanisms. Emerging studies have revealed widespread roles of lncRNAs in the regulation of various cellular activities, including metabolic pathways. In this review, we summarize the latest advances regarding the regulatory roles of lncRNAs in cancer metabolism, particularly their roles in mitochondrial function, glucose, glutamine, and lipid metabolism. Moreover, we discuss the clinical application and challenges of targeting lncRNAs in cancer metabolism. Understanding the complex and special behavior of lncRNAs will allow a better depiction of cancer metabolic networks and permit the development of lncRNA-based clinical therapies by targeting cancer metabolism.

Background Hypoxia is an important characteristic of the tumor microenvironment. Tumor cells can survive and propagate under the hypoxia stress through activating a series of adaption response. The study on the mechanism of tumor hypoxia adaption is still of urgent significance to find effective therapeutic targets and strategies. Methods We compared the protein expression of KDM5B in tumor or normal tissues and cell lines by IHC and Western blotting (WB). CCK8 and cell colony formation assay was performed to evaluate the KDM5B caused growth inhibition. The transcriptome analysis, quantitative real-time PCR (qPCR), flow cytometry analysis, chromatin immunoprecipitation (ChIP) were for exploring the downstream mechanism. And the SUMOylation assay and Ni-beads pull-down assay and co-immunoprecipitation (co-IP) were used to illustrate how did post-translation modification (PTM) regulate the KDM5B protein stabilization. Finally, tumor xenograft assay in nude mice verified the findings in vivo. Results We found that lysine-specific demethylase 5B (KDM5B) was upregulated in gastric cancer (GC) under hypoxia condition. The genetic knockdown or chemical inhibition of KDM5B impaired the growth of GC cell adapted to hypoxia. Inhibition of KDM5B caused significant cell cycle G1/S arrest through the transcription upregulation of cyclin-dependent kinase inhibitor 1 (CDKN1, also known as p21). Interestingly, the upregulation of KDM5B in hypoxia response was associated with the SUMOylation of KDM5B. SUMOylation stabilized KDM5B protein by reducing the competitive modification of ubiquitination. Furthermore, protein inhibitor of activated STAT 4 (PIAS4) was determined as the SUMO E3 ligase which increased the interaction with KDM5B under hypoxia condition. As the result, co-targeting KDM5B significantly improved the anti-tumor efficacy of antiangiogenic therapy in vivo. Conclusion Taken together, PIAS4 mediated SUMOylation stabilized KDM5B protein through disturbing ubiquitination-dependent proteasomal degradation to overcome hypoxia adaption. Targeting SUMOylation-dependent KDM5B upregulation might be considered when antiangiogenic therapy was applied in cancer treatment.

Abnormal neddylation activation is frequently observed in human cancers and neddylation inhibition has been proposed as a therapy for cancer. Here, we report that MLN4924, a small-molecule inhibitor of neddylation activating enzyme, increases glutamine uptake in breast cancer cells by causing accumulation of glutamine transporter ASCT2/SLC1A5, via inactivation of CRL3-SPOP E3 ligase. We show the E3 ligase SPOP promotes ASCT2 ubiquitylation, whereas SPOP itself is auto-ubiquitylated upon glutamine deprivation. Thus, SPOP and ASCT2 inversely regulate glutamine uptake and metabolism. SPOP knockdown increases ASCT2 levels to promote growth which is rescued by ASCT2 knockdown. Adding ASCT2 inhibitor V-9302 enhances MLN4924 suppression of tumor growth. In human breast cancer specimens, SPOP and ASCT2 levels are inversely correlated, whereas lower SPOP with higher ASCT2 predicts a worse patient survival. Collectively, our study links neddylation to glutamine metabolism via the SPOP-ASCT2 axis and provides a rational drug combination for enhanced cancer therapy.

Chemoresistance is one of the most important challenges in the clinical management of lung cancer. SIRT1 is a NAD dependent protein deacetylase and implicated in diverse cellular processes such as DNA damage repair, and cancer progression. SIRT1 is upregulated in chemoresistant lung cancer cells, genetic knockdown or chemical inhibition of SIRT1 reversed chemoresistance by enhancing DNA damage and apoptosis activation, accompanied with XRCC1 degradation. E3 ligase β-TrCP catalyzed the poly-ubiquitination of XRCC1 to promote its proteasome-dependent degradation. SIRT1 bound and deacetylated XRCC1 at lysine K260, K298 and K431, preventing it from β-TrCP-dependent ubiquitination. Mutations of these three lysine sites in XRCC1 abrogated the interaction with β-TrCP and prolonged the half-life of XRCC1 protein. Here, we describes SIRT1 confers chemoresistance to lung cancer cells by deacetylating and stabilizing XRCC1. Therefore, targeting SIRT1 might be a new strategy to manage the chemoresistance of lung cancer, and probably other cancers.

Background & Aims: Dysregulation of metabolism plays an important role in the development and progression of cancers, while the underlying mechanisms remain largely unknown. This study aims to explore the regulation and relevance of glycolysis in chemoresistance of gastric cancer. Methods: Biochemical differences between chemoresistant and chemosensitive cancer cells were determined by metabolism profiling, microarray gene expression, PCR or western blotting. Cancer cell growth in vitro or in vivo were analyzed by viability, apoptosis and nude mice assay. Immunoprecipation was used to explore the interaction of proteins with other proteins or DNAs. Results: By metabolic and gene expression profiling, we found that pyruvate dehydrogenase kinase 3 (PDK3) was highly expressed to promote glycolysis in chemoresistant cancer cells. Its genetic or chemical inhibition reverted chemoresistance in vitro and in vivo. It was transcriptionally regulated by transcription factor HSF1 (Heat shock factor 1). Interestingly, PDK3 can localize in the nucleus and interact with HSF1 to disrupt its phosphorylation by GSK3β. Since HSF1 was subjected to FBXW7-catalyzed polyubiquitination in a phosphorylation-dependent manner, PDK3 prevented HSF1 from proteasomal degradation. Thus, metabolic enzyme PDK3 and transcription factor HSF1 forms a positive feedback loop to promote glycolysis. As a result, inhibition of HSF1 impaired enhanced glycolysis and reverted chemoresistance both in vitro and in vivo. Conclusions: PDK3 forms a positive feedback loop with HSF1 to drive glycolysis in chemoresistance. Targeting this mitonuclear communication may represent a novel approach to overcome chemoresistance.

p62/SQSTM1 is frequently up-regulated in many cancers including hepatocellular carcinoma. Highly expressed p62 promotes hepato-carcinogenesis by activating many signaling pathways including Nrf2, mTORC1, and NFκB signaling. However, the underlying mechanism for p62 up-regulation in hepatocellular carcinoma remains largely unclear. Herein, we confirmed that p62 was up-regulated in hepatocellular carcinoma and its higher expression was associated with shorter overall survival in patients. The knockdown of p62 in hepatocellular carcinoma cells decreased cell growth in vitro and in vivo. Intriguingly, p62 protein stability could be reduced by its acetylation at lysine 295, which was regulated by deacetylase Sirt1 and acetyltransferase GCN5. Acetylated p62 increased its association with the E3 ligase Keap1, which facilitated its poly-ubiquitination-dependent proteasomal degradation. Moreover, Sirt1 was up-regulated to deacetylate and stabilize p62 in hepatocellular carcinoma. Additionally, Hepatocyte Sirt1 conditional knockout mice developed much fewer liver tumors after Diethynitrosamine treatment, which could be reversed by the re-introduction of exogenous p62. Taken together, Sirt1 deacetylates p62 at lysine 295 to disturb Keap1-mediated p62 poly-ubiquitination, thus up-regulating p62 expression to promote hepato-carcinogenesis. Therefore, targeting Sirt1 or p62 is a reasonable strategy for the treatment of hepatocellular carcinoma.

Mitochondria are the powerhouse of a cell. The structure and function of mitochondria are precisely regulated by multiple signaling pathways. Neddylation, a post-translational modification, plays a crucial role in various cellular processes including cellular metabolism via modulating the activity, function and subcellular localization of its substrates. Recently, accumulated data demonstrated that neddylation is involved in regulation of morphology, trafficking and function of mitochondria. Mechanistic elucidation of how mitochondria is modulated by neddylation would further our understanding of mitochondrial regulation to a new level. In this review, we first briefly introduce mitochondria, then neddylation cascade, and known protein substrates subjected to neddylation modification. Next, we summarize current available data of how neddylation enzymes, its substrates (including cullins/Cullin-RING E3 ligases and non-cullins) and its inhibitor MLN4924 regulate the structure and function of mitochondria. Finally, we propose the future perspectives on this emerging and exciting field of mitochondrial research.

Qiyin Zhou,* Xi Lan,* Ni Li, Daozu Yuan, Jiliang Zhang Department of Oncology, Chengdu Seventh People Hospital (Chengdu Tumorous Disease Quality Control Center), Chengdu 610000, People’s Republic of China*These authors contributed equally to this workCorrespondence: Jiliang ZhangDepartment of Oncology, Chengdu Seventh People Hospital (Chengdu Tumorous Disease Quality Control Center), 51 Zhimin Road, Chengdu 610000, People’s Republic of ChinaTel +86 13982070262Email Zhangjiliang126@126.comBackground: This study was to investigate the prognostic factors of patients with advanced gastric cancer and described a sample model to better differentiate the patients who could better benefit from palliative chemotherapy.Patients and Methods: In this retrospective study, 112 gastric cancer patients at stage IV following first-line chemotherapy were enrolled from July 2013 to September 2019. The clinical factors including age, sex, ECOG, pathologic types, metastatic sites, blood indexes, response of first-line chemotherapy, and survival were collected. The treatment responses were evaluated using the response evaluation criteria in solid tumors (RECIST). The survival curves were drawn by the Kaplan–Meier method, and the independent prognostic factors of overall survival (OS) were analyzed by Cox proportional hazards regression model.Results: In this study, the median overall survival (mOS) of gastric cancer patients was 10.5 months, the disease remission rate (PR) was 21.4%, and the disease control rate (DCR) was 86.6%. Multivariate analysis identified 5 independent prognostic factors: peritoneal metastasis [P = 0.002; hazard risk (HR), 2.394; 95% CI 1.394– 4.113], hemoglobin < 90g/L [P = 0.001; hazard risk (HR), 2.674; 95% CI 1.536– 4.655], LDH ≥ 225 U/L [P = 0.033; hazard risk (HR), 1.818; 95% CI 1.409– 3.150], and 3 times higher level of CEA [P = 0.006; hazard risk (HR), 2.123; 95% CI 1.238– 3.640] along with CA199 [P = 0.005; hazard risk (HR), 2.544; 95% CI 1.332– 4.856] than upper limit of normal. Based on the obtained data, a prognostic index was constructed, dividing the patients into three risk groups: low (n = 67), intermediate (n = 35), and high-risk group (n = 10). The mOS for low, intermediate, and high-risk groups was 13.9 months (95% CI 10.7– 17.1), 8.1 months (95% CI 5.7– 10.4), and 3.9 months (95% CI 2.6– 5.3), respectively, whereas the 1-year survival rate was 56.4%, 20.0%, and 0.0%, respectively (P < 0.001).Conclusion: This model should facilitate the prediction of treatment outcomes and then individualized treatment of advanced gastric cancer patients.Keywords: prognostic factor, advanced gastric cancer, prognosis model, first-line chemotherapy

Additional file 2: Supplemnetary Figures 1-6. Fig. S1. WNT/β-catenin signaling activates HSF1. Fig. S2. β-catenin has no effects on the RNA and protein half-life of HSF1. Fig. S3. The effect of microRNAs on HSF1 expression in CRC. Fig. S4. m6A modification of HSF1 mRNA. Fig. S5. The effects of miR455-3p and m6A modification on HSF1. Fig. S6. Volcano plot displays differentially regulated genes upon LiCl treatment.

// Jiaqiu Li 1, 2 , Ping Song 1 , Liyuan Zhu 2 , Neelum Aziz 1 , Qiyin Zhou 1 , Yulong Zhang 2 , Wenxia Xu 2 , Lifeng Feng 2 , Dingwei Chen 3 , Xian Wang 1 and Hongchuan Jin 2 1 Department of Medical Oncology, Sir Runrun Shaw Hospital, Medical School of Zhejiang University, Hangzhou, China 2 Laboratory of Cancer Biology, Key Lab of Biotherapy in Zhejiang, Sir Runrun Shaw Hospital, Medical School of Zhejiang University, Hangzhou, China 3 Department of Surgery, Sir Runrun Shaw Hospital, Medical School of Zhejiang University, Hangzhou, China Correspondence to: Dingwei Chen, email: dwyf@hotmail.com Xian Wang, email: wangxzju@163.com Hongchuan Jin, email: jinhc@zju.edu.cn Keywords: colorectal cancer, glutaminolysis, glutamine, synthetic lethality Received: December 21, 2016 Accepted: March 17, 2017 Published: April 05, 2017 ABSTRACT Cancer cells reprogram metabolism to coordinate their rapid growth. They addict on glutamine metabolism for adenosine triphosphate generation and macromolecule biosynthesis. In this study, we report that glutamine deprivation retarded cell growth and induced prosurvival autophagy. Autophagy inhibition by chloroquine significantly enhanced glutamine starvation induced growth inhibition and apoptosis activation. Asparagine deprivation by L-asparaginase exacerbated growth inhibition induced by glutamine starvation and autophagy blockage. Similar to glutamine starvation, inhibition of glutamine metabolism with a chemical inhibitor currently under clinical evaluation was synthetically lethal with chloroquine and L-asparaginase, drugs approved for the treatment of malaria and leukemia, respectively. In conclusion, inhibiting glutaminolysis was synthetically lethal with autophagy inhibition and asparagine depletion. Therefore, targeting glutaminolysis could be a promising approach for colorectal cancer treatment.

Abnormal activation of neddylation modification and dysregulated energy metabolism are frequently seen in many types of cancer cells. Whether and how neddylation modification affects cellular metabolism remains largely unknown. Here, we showed that MLN4924, a small-molecule inhibitor of neddylation modification, induces mitochondrial fission-to-fusion conversion in breast cancer cells via inhibiting ubiquitylation and degradation of fusion-promoting protein mitofusin 1 (MFN1) by SCF(β-TrCP) E3 ligase and blocking the mitochondrial translocation of fusion-inhibiting protein DRP1. Importantly, MLN4924-induced mitochondrial fusion is independent of cell cycle progression, but confers cellular survival. Mass-spectrometry-based metabolic profiling and mitochondrial functional assays reveal that MLN4924 inhibits the TCA cycle but promotes mitochondrial OXPHOS. MLN4924 also increases glycolysis by activating PKM2 via promoting its tetramerization. Biologically, MLN4924 coupled with the OXPHOS inhibitor metformin, or the glycolysis inhibitor shikonin, significantly inhibits cancer cell growth both in vitro and in vivo. Together, our study links neddylation modification and energy metabolism, and provides sound strategies for effective combined cancer therapies.

Objective The aim of this study is to report the clinical application of noninvasive prenatal testing (NIPT) to detect chromosomal aneuploidies, especially trisomies 21, 18, and 13 in Chinese singleton pregnancies. Methods Pilot validation between NIPT with full karyotyping was conducted blindly on 306 cases. Subsequently, 7705 pregnancies were offered with NIPT. Follow-up data was obtained in all cases. Results In the validation stage, a total of five NIPT positive cases were observed for trisomies 21 and 18, and results were confirmed by karyotyping; there were no cases of trisomy 13. Thus, the overall sensitivity and specificity in the validation stage was 100%. In 7705 cases, NIPT results were obtained in 7701 cases; 66 cases were classified as positive, including 48 cases of trisomy 21, 14 cases of trisomy 18, and 4 cases of trisomy 13. Subsequent karyotyping documented two false positive diagnoses for trisomies 21, 18, and 13, respectively. Sensitivity and specificity for detection of trisomies 21 and 18 and 13 were 100% and 99.9%, respectively. Additionally, prenatal chromosomal detection for pregnancies with NIPT has shown a gradual increase since its implementation. Conclusion Noninvasive prenatal testing allows a more suitable and efficient workflow for our patients' needs, together withinvasive proceduresallowsa higherprenataldetectionofchromosomal aneuploidies.©2014JohnWiley& Sons,Ltd.

Eight ent-kaurene diterpenoids were isolated from three Isodon plants, Isodon excisoides (Sun ex C. H. Hu) C. Y. Wu et H. W. Li, Isodon weisiensis C. Y. Wu, and Isodon racemosa (Hemsl.) Hara. Their cytotoxicities were tested by SRB assay against four human tumor cell lines, HepG2, Tb, HO-8910 and SGC-7901. The DNA damage degrees on their Hep G2 cells were evaluated by Comet assay. The results showed that ent-kaurene diterpenoids were selectively toxic against these four tumor cell lines. Weisiensic C had the lowest cytotoxicity against four cell lines and degree of DNA damage on the Hep G2 cell line. Leukamenin E and Glaucocalyxin A had similar IC50 values and also induced a similar degree of DNA damage. The cytotoxicity and degree of DNA damage of eight ent-kaurene diterpenoids on Hep G2 was in the order Leukamenin E > Glaucocalyxin A > Wangzaozin A > Kamebanin > Macrocalyxin D > Weisiensin B > Excisanin K > Weisiensic C. The structure–activity relationships indicated that there was some correlation between the substituents and their structures of ent-kaurene diterpenoids and their activities on Hep G2 cells.

The aim of this study is to report the clinical application of noninvasive prenatal testing (NIPT) to detect chromosomal aneuploidies, especially trisomies 21, 18, and 13 in Chinese singleton pregnancies.Pilot validation between NIPT with full karyotyping was conducted blindly on 306 cases. Subsequently, 7705 pregnancies were offered with NIPT. Follow-up data was obtained in all cases.In the validation stage, a total of five NIPT positive cases were observed for trisomies 21 and 18, and results were confirmed by karyotyping; there were no cases of trisomy 13. Thus, the overall sensitivity and specificity in the validation stage was 100%. In 7705 cases, NIPT results were obtained in 7701 cases; 66 cases were classified as positive, including 48 cases of trisomy 21, 14 cases of trisomy 18, and 4 cases of trisomy 13. Subsequent karyotyping documented two false positive diagnoses for trisomies 21, 18, and 13, respectively. Sensitivity and specificity for detection of trisomies 21 and 18 and 13 were 100% and 99.9%, respectively. Additionally, prenatal chromosomal detection for pregnancies with NIPT has shown a gradual increase since its implementation.Noninvasive prenatal testing allows a more suitable and efficient workflow for our patients' needs, together with invasive procedures allows a higher prenatal detection of chromosomal aneuploidies.

Background Hypertrophic cardiomyopathy (HCM) is a primary disorder characterised by asymmetric thickening of septum and left ventricular wall, with a prevalence of 0.2% in the general population. Objective To describe a novel mitochondrial DNA mutation and its association with the pathogenesis of HCM. Methods and results All maternal members of a Chinese family with maternally transmitted HCM exhibited variable severity and age at onset, and were implanted permanent pacemakers due to complete atrioventricular block (AVB). Nuclear gene screening ( MYH7 , MYBPC3 , TNNT2 and TNNI3 ) was performed, and no potential pathogenic mutation was identified. Mitochondrial DNA sequencing analysis identified a novel homoplasmic 16S rRNA 2336T>C mutation. This mutation was exclusively present in maternal members and absent in non-maternal members. Conservation index by comparison to 16 other vertebrates was 94.1%. This mutation disturbs the 2336U-A2438 base pair in the stem–loop structure of 16S rRNA domain III, which is involved in the assembly of mitochondrial ribosome. Oxygen consumption rate of the lymphoblastoid cells carrying 2336T>C mutation had decreased by 37% compared with controls. A reduction in mitochondrial ATP synthesis and an increase in reactive oxidative species production were also observed. Electron microscopic analysis indicated elongated mitochondria and abnormal mitochondrial cristae shape in mutant cells. Conclusions It is suggested that the 2336T>C mutation is one of pathogenic mutations of HCM. This is the first report of mitochondrial 16S rRNA 2336T>C mutation and an association with maternally inherited HCM combined with AVB. Our findings provide a new insight into the pathogenesis of HCM.

Background Hyperfibrinogenemia is a common problem associated with various carcinomas, and is accompanied by hypercoagulablity. In advanced non-small-cell lung cancer (NSCLC) it remains unclear whether or not chemotherapy-induced changes in fibrinogen level relate to chemotherapeutic response and prognosis. The purposes of this study were to: 1) analyze the association between chemotherapy-induced changes in plasma fibrinogen level and the chemotherapeutic response after the first two courses of standard first-line platinum-based chemotherapy; and 2) evaluate the prognostic significance of the basal plasma fibrinogen level in patients with advanced NSCLC. Methods In this retrospective study, the data from 160 patients with advanced NSCLC were collected. The association between the changes in fibrinogen and the response to chemotherapy, or between the pre-and post-chemotherapy fibrinogen levels and patient clinical characteristics, were analyzed using SPSS software. In addition, the prognostic value of pre-chemotherapy fibrinogen levels was assessed. Results The median pre-chemotherapy plasma fibrinogen level was 4.4 g/L. Pre-chemotherapy plasma fibrinogen levels correlated significantly with gender (p = 0.041). Post-chemotherapy plasma fibrinogen levels correlated with gender (p = 0.023), age (p = 0.018), ECOG (p = 0.002) and tumor response (p = 0.049). Plasma fibrinogen levels markedly decreased after chemotherapy in 98 (61.25 %) patients with pre-chemotherapy hyperfibrinogenemia (p = 0.008); and in this population there was a significant link between the decrease in fibrinogen level, and initial partial response (PR; p = 0.017) and stable disease (SD; p = 0.031). Univariate and multivariate analysis revealed that higher levels of fibrinogen (≥4.4 g/L) and ECOG 1 were positively associated with shorter overall survival (OS). CEA and CA125 also decreased significantly (p =0.015, p =0.000) in DCR group after chemotherapy. Conclusions This study showed that the reduction in plasma fibrinogen levels induced by chemotherapy might be as a promising biomarker as CEA and CA125 for evaluating the efficacy of chemotherapy in advanced NSCLC. In addition, basal plasma fibrinogen levels could be used as an independent prognostic parameter for the OS of patients with advanced NSCLC.

MTO1, together with MSS1 and MTO2, is a gene involved in the pathway of encoding a mitochondria-specific RNA-modifying enzyme related to the post-transcriptional modification of mitochondrial tRNAs. We have previously shown that a mutation of the MTO2 or MSS1 gene can suppress the neomycin-sensitive phenotype of yeast carrying a mitochondrial 15S rRNA C1477G mutation. Here we report that a null mutation of MTO1 also can inhibit the aminoglycoside-sensitivity of yeast carrying mitochondrial 15S rRNA C1477G mutation. The C1477G mutation corresponds to the human 12S rRNA A1555G mutation. Yeast with an mtDNA C1477G mutation exhibits hypersensitivity to neomycin and displays mitochondrial function impairment beyond neomycin treatment. When the mto1 null mutation and mitochondrial C1477G mutation coexist, the yeast strain shows growth recovery. The deletion of the nuclear gene MTO1 regulates neomycin sensitivity in yeast carrying the mitochondrial 15S rRNA C1477G mutation. MTO1 deletion causes the expression levels of the key glycolytic genes HXK2, PFK1 and PYK1 to become significantly up-regulated. The energy deficit due to impaired mitochondrial function was partially compensated by the energy generated by glycolysis. Being in the same pathway, the regulation of MTO1, MSS1 and MTO2 to the neomycin-sensitivity of yeast showed difference in the growth activity of strains, mitochondrial function and the expression level of glycolytic genes.

The phenotypic manifestation of mitochondrial DNA (mtDNA) mutations can be modulated by nuclear genes and environmental factors. However, neither the interaction among these factors nor their underlying mechanisms are well understood. The yeast Saccharomyces cerevisiae mtDNA 15S rRNA C1477G mutation (PR) corresponds to the human 12S rRNA A1555G mutation. Here we report that a nuclear modifier gene mss1 mutation suppresses the neomycin-sensitivity phenotype of a yeast C1477G mutant in fermentable YPD medium. Functional assays show that the mitochondrial function of the yeast C1477G mutant was impaired severely in YPD medium with neomycin. Moreover, the mss1 mutation led to a significant increase in the steady-state level of HAP5 (heme activated protein), which greatly up-regulated the expression of glycolytic transcription factors RAP1, GCR1, and GCR2 and thus stimulated glycolysis. Furthermore, the high expression of the key glycolytic enzyme genes HXK2, PFK1 and PYK1 indicated that enhanced glycolysis not only compensated for the ATP reduction from oxidative phosphorylation (OXPHOS) in mitochondria, but also ensured the growth of the mss1(PR) mutant in YPD medium with neomycin. This study advances our understanding of the phenotypic manifestation of mtDNA mutations.