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CaMKII has long been known to be a key effector for synaptic plasticity. Recent studies have shown that a variety of modulators interact with the subunits of CaMKII to regulate the long-term potentiation (LTP) of hippocampal neurons. However, whether long non-coding RNAs modulate the activity of CaMKII and affect synaptic plasticity is still elusive. Here, we identify a previously uncharacterized long non-coding RNA Carip that functions as a scaffold, specifically interacts with CaMKIIβ, and regulates the phosphorylation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-d-aspartate (NMDA) receptor subunits in the hippocampus. The absence of Carip causes dysfunction of synaptic transmission and attenuates LTP in hippocampal CA3-CA1 synapses, which further leads to impairment of spatial learning and memory. In summary, our findings demonstrate that Carip modulates long-term synaptic plasticity by changing AMPA receptor and NMDA receptor activities, thereby affecting spatial learning and memory in mice.

Homologous recombination (HR) is often used to achieve targeted gene integration because of its higher precision and operability compared with microhomology-mediated end-joining (MMEJ) or non-homologous end-joining (NHEJ). It appears to be inefficient for gene integration in animal cells and embryos due to occurring only during cell division. Here we developed genome-wide high-throughput screening and a subsequently paired crRNA library screening to search for genes suppressing homology-directed repair (HDR). We found that, in the reporter system, HDR cells with knockdown of SHROOM1 were enriched as much as 4.7-fold than those with control. Down regulating SHROOM1 significantly promoted gene integration in human and mouse cells after cleavage by clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein-9 nuclease (Cas9), regardless of the donor types. The knock-in efficiency of mouse embryos could also be doubled by the application of SHROOM1 siRNA during micro-injection. The increased HDR efficiency of SHROOM1 deletion in HEK293T cells could be counteracted by YU238259, an HDR inhibitor, but not by an NHEJ inhibitor. These results indicated that SHROOM1 was an HDR-suppressed gene and that the SHROOM1 knockdown strategy may be useful for a variety of applications, including gene editing to generate cell lines and animal models for studying gene function and human diseases.

Homologous recombination (HR) is often used to achieve targeted gene integration because of its higher precision and operability compared with microhomology-mediated end-joining (MMEJ) or non-homologous end-joining (NHEJ). It appears to be inefficient for gene integration in animal cells and embryos due to occurring only during cell division. Here we developed genome-wide high-throughput screening and a subsequently paired crRNA library screening to search for genes suppressing homology-directed repair (HDR). We found that, in the reporter system, HDR cells with knockdown of SHROOM1 were enriched as much as 4.7-fold than those with control. Down regulating SHROOM1 significantly promoted gene integration in human and mouse cells after cleavage by clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein-9 nuclease (Cas9), regardless of the donor types. The knock-in efficiency of mouse embryos could also be doubled by the application of SHROOM1 siRNA during micro-injection. The increased HDR efficiency of SHROOM1 deletion in HEK293T cells could be counteracted by YU238259, an HDR inhibitor, but not by an NHEJ inhibitor. These results indicated that SHROOM1 was an HDR-suppressed gene and that the SHROOM1 knockdown strategy may be useful for a variety of applications, including gene editing to generate cell lines and animal models for studying gene function and human diseases.

Several patient-derived tumor models emerged recently as robust preclinical drug-testing platforms. However, their potential to guide clinical therapy remained unclear. Here, we report a model called patient-derived tumor-like cell clusters (PTCs). PTCs result from the self-assembly and proliferation of primary epithelial, fibroblast, and immune cells, which structurally and functionally recapitulate original tumors. PTCs enabled us to accomplish personalized drug testing within 2 weeks after obtaining the tumor samples. The defined culture conditions and drug concentrations in the PTC model facilitate its clinical application in precision oncology. PTC tests of 59 patients with gastric, colorectal, or breast cancers revealed an overall accuracy of 93% in predicting their clinical outcomes. We implemented PTC to guide chemotherapy selection for a patient with mucinous rectal adenocarcinoma who experienced recurrence with metastases after conventional therapy. After three cycles of a nonconventional therapy identified by the PTC, the patient showed a positive response. These findings need to be validated in larger clinical trials, but they suggest that the PTC model could be prospectively implemented in clinical decision-making for therapy selection.

Additional file 1. Additional figures and tables.

Summary: It is still a challenge for synthesizing ‘cellular niche-mimics’ in vitro with satisfactory reproducibility and fidelity to recreate the natural niche components (e.g., extracellular matrices and soluble factors) for stem cell cultivation. Inspired by the massive amplification of hepatic progenitor cells during liver fibrosis in vivo, here we optimized the in vitro liver fibrotic niches and subsequently harvested their bioactive ingredients as niche extracts (NEs). The fibrosis-relevant NE marginally outperformed Matrigel for phenotype maintenance of human embryonic stem cell (hESC)-derived hepatoblasts (HBs) and recapitulation of the pathological angiogenesis of hESC-derived endothelial cells both in 2D culture and 3D liver organoids. Finally, defined NE components (i.e., collagen III, IV, IL-17, IL-18 and M-CSF) were resolved by the quantitative proteomics which exhibited advantage over Matrigel for multi-passaged HB expansion. The pathology-relevant and tissue-specific NEs provide innovative and generalizable strategies for the discovery of optimal cellular niche and bioactive niche compositions.

Summary The ever-increasing understanding of the complexity of factors and regulatory layers that contribute to immune evasion facilitates the development of immunotherapies. However, the diversity of malignant tumors limits many known mechanisms in specific genetic and epigenetic contexts, manifesting the need to discover general driver genes. Here, we have identified the m6A demethylase FTO as an essential epitranscriptomic regulator utilized by tumors to escape immune surveillance through regulation of glycolytic metabolism. We show that FTO-mediated m6A demethylation in tumor cells elevates the transcription factors c-Jun, JunB, and C/EBPβ, which allows the rewiring of glycolytic metabolism. Fto knockdown impairs the glycolytic activity of tumor cells, which restores the function of CD8+ T cells, thereby inhibiting tumor growth. Furthermore, we developed a small-molecule compound, Dac51, that can inhibit the activity of FTO, block FTO-mediated immune evasion, and synergize with checkpoint blockade for better tumor control, suggesting reprogramming RNA epitranscriptome as a potential strategy for immunotherapy.

Efficient generation of mice carrying homozygous double-floxp alleles using the Cas9-Avidin/Biotin-donor DNA system

Heart diseases such as myocardial infarction and myocardial ischemia are paroxysmal and fatal in clinical practice. Cardiomyocytes (CMs) differentiated from human pluripotent stem cells provide a promising approach to myocardium regeneration therapy. Identifying the maturity level of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) is currently the main challenge for pathophysiology and therapeutics. In this review, we describe current maturity indicators for cardiac microtissue and microdevice cultivation technologies that accelerate cardiac maturation. It may provide insights into regenerative medicine, drug cardiotoxicity testing, and preclinical safety testing.

Transcription activator-like effectors (TALEs) are becoming powerful DNA-targeting tools in a variety of mammalian cells and model organisms. However, generating a stable cell line with specific gene mutations in a simple and rapid manner remains a challenging task. Here, we report a new method to efficiently produce monoclonal cells using integrated TALE nuclease technology and a series of high-throughput cell cloning approaches. Following this method, we obtained three mTOR mutant 293T cell lines within 2 months, which included one homozygous mutant line.

This report demonstrates a straightforward, robust, multiplexed and point-of-care microcapillary-based loop-mediated isothermal amplification (cLAMP) for assaying nucleic acids. This assay integrates capillaries (glass or plastic) to introduce and house sample/reagents, segments of water droplets to prevent contamination, pocket warmers to provide heat, and a hand-held flashlight for a visual readout of the fluorescent signal. The cLAMP system allows the simultaneous detection of two RNA targets of human immunodeficiency virus (HIV) from multiple plasma samples, and achieves a high sensitivity of two copies of standard plasmid. As few nucleic acid detection methods can be wholly independent of external power supply and equipment, our cLAMP holds great promise for point-of-care applications in resource-poor settings.

The Pyrin inflammasome detects the presence of a pathogen not through recognition of a microbial molecule but by the activity of a bacterial toxin that modifies host Rho activity. The inflammasome complex, mediated by NOD-like receptor (NLR) proteins or other Pyrin-domain pattern recognition receptors (PRRs), plays a critical role in innate immune defence against various microbial infections. Feng Shao and colleagues show that the Pyrin inflammasome detects the presence of the pathogen Burkholderia cenocepacia not by recognizing a microbial molecule, the mechanism commonly adopted by mammalian PRRs, but by sensing the response of host Rho GTPase to a bacterial toxin. Infection with B. cenocepacia is of clinical importance as it can often be fatal in cystic fibrosis and chronic granulomatous disease, therefore the findings reported here could be of relevance to vaccine development and immunotherapy prevention against this type of pathogen. Cytosolic inflammasome complexes mediated by a pattern recognition receptor (PRR) defend against pathogen infection by activating caspase 1. Pyrin, a candidate PRR, can bind to the inflammasome adaptor ASC to form a caspase 1-activating complex1,2. Mutations in the Pyrin-encoding gene, MEFV, cause a human autoinflammatory disease known as familial Mediterranean fever3,4,5. Despite important roles in immunity and disease, the physiological function of Pyrin remains unknown. Here we show that Pyrin mediates caspase 1 inflammasome activation in response to Rho-glucosylation activity of cytotoxin TcdB6,7,8, a major virulence factor of Clostridium difficile, which causes most cases of nosocomial diarrhoea. The glucosyltransferase-inactive TcdB mutant loses the inflammasome-stimulating activity. Other Rho-inactivating toxins, including FIC-domain adenylyltransferases (Vibrio parahaemolyticus VopS and Histophilus somni IbpA) and Clostridium botulinum ADP-ribosylating C3 toxin, can also biochemically activate the Pyrin inflammasome in their enzymatic activity-dependent manner. These toxins all target the Rho subfamily and modify a switch-I residue. We further demonstrate that Burkholderia cenocepacia inactivates RHOA by deamidating Asn 41, also in the switch-I region, and thereby triggers Pyrin inflammasome activation, both of which require the bacterial type VI secretion system (T6SS). Loss of the Pyrin inflammasome causes elevated intra-macrophage growth of B. cenocepacia and diminished lung inflammation in mice. Thus, Pyrin functions to sense pathogen modification and inactivation of Rho GTPases, representing a new paradigm in mammalian innate immunity.

Cell metabolism is critical for cancer cell transformation and progression. In this study, we have developed a novel method, named Met-express, that integrates a cancer gene co-expression network with the metabolic network to predict key enzyme-coding genes and metabolites in cancer cell metabolism. Met-express successfully identified a group of key enzyme-coding genes and metabolites in lung, leukemia, and breast cancers. Literature reviews suggest that approximately 33-53% of the predicted genes are either known or suggested anti-cancer drug targets, while 22% of the predicted metabolites are known or high-potential drug compounds in therapeutic use. Furthermore, experimental validations prove that 90% of the selected genes and 70% of metabolites demonstrate the significant anti-cancer phenotypes in cancer cells, implying that they may play important roles in cancer metabolism. Therefore, Met-express is a powerful tool for uncovering novel therapeutic biomarkers.

Myocardial infarction (MI) is the most common cause of heart failure. Excessive production of ROS plays a key role in the pathogenesis of cardiac remodeling after MI. NADPH with NADPH oxidase (Nox)2 as the catalytic subunit is a major source of superoxide production, and expression is significantly increased in the infarcted myocardium, especially by infiltrating macrophages. While microRNAs (miRNAs) are potent regulators of gene expression and play an important role in heart disease, there still lacks efficient ways to identify miRNAs that target important pathological genes for treating MI. Thus, the overall objective was to establish a miRNA screening and delivery system for improving heart function after MI using Nox2 as a critical target. With the use of the miRNA-target screening system composed of a self-assembled cell microarray (SAMcell), three miRNAs, miR-106b, miR-148b, and miR-204, were identified that could regulate Nox2 expression and its downstream products in both human and mouse macrophages. Each of these miRNAs were encapsulated into polyketal (PK3) nanoparticles that could effectively deliver miRNAs into macrophages. Both in vitro and in vivo studies in mice confirmed that PK3-miRNAs particles could inhibit Nox2 expression and activity and significantly improve infarct size and acute cardiac function after MI. In conclusion, our results show that miR-106b, miR-148b, and miR-204 were able to improve heart function after myocardial infarction in mice by targeting Nox2 and possibly altering inflammatory cytokine production. This screening system and delivery method could have broader implications for miRNA-mediated therapeutics for cardiovascular and other diseases. NEW & NOTEWORTHY NADPH oxidase (Nox)2 is a promising target for treating cardiovascular disease, but there are no specific inhibitors. Finding endogenous signals that can target Nox2 and other inflammatory molecules is of great interest. In this study, we used high-throughput screening to identify microRNAs that target Nox2 and improve cardiac function after infarction.

Pigs are ideal organ donors for xenotransplantation and an excellent model for studying human diseases, such as neurodegenerative disease. Transcription activator-like effector nucleases (TALENs) are used widely for gene targeting in various model animals. Here, we developed a strategy using TALENs to target the GGTA1, Parkin and DJ-1 genes in the porcine genome using Large White porcine fibroblast cells without any foreign gene integration. In total, 5% (2/40), 2.5% (2/80), and 22% (11/50) of the obtained colonies of fibroblast cells were mutated for GGTA1, Parkin, and DJ-1, respectively. Among these mutant colonies, over 1/3 were bi-allelic knockouts (KO), and no off-target cleavage was detected. We also successfully used single-strand oligodeoxynucleotides to introduce a short sequence into the DJ-1 locus. Mixed DJ-1 mutant colonies were used as donor cells for somatic cell nuclear transfer (SCNT), and three female piglets were obtained (two were bi-allelically mutated, and one was mono-allelically mutated). Western blot analysis showed that the expression of the DJ-1 protein was disrupted in KO piglets. These results imply that a combination of TALENs technology with SCNT can efficiently generate bi-allelic KO pigs without the integration of exogenous DNA. These DJ-1 KO pigs will provide valuable information for studying Parkinson's disease.

VEGF is a major contributor to angiogenesis, a vital process in normal growth and development and tumor transition. However, the current clinical efficacy of VEGF inhibitors is limited, and the molecular mechanism underlying VEGF regulation remains to be elucidated. Here we show that miR-190 directly targets a group of angiogenic effectors besides VEGF per se. Noted, these effectors can transcriptionally regulate VEGF expression in an intracellular or intercellular manner, thus demonstrating that miR-190 modulates the VEGF-mediated tumor angiogenesis at three levels. The synergistic effect of miR-190 and its target genes demonstrates a complex but apparently more stable system, allowing for the tight control of the level of VEGF. Finally, we showed that miR-190 significantly suppresses tumor metastasis, especially angiogenesis. Together, these results indicate that miR-190 is a promising antitumor target in clinical applications.

Tumor suppressor TP53 (or p53) is one of the most important regulators in numerous physiological and pathological processes. Recently, the miRNA-mediated post-transcription regulation of p53 has been studied. However, systematic studies of miRNA targeting sites within the p53 gene are still a challenging task. Here, we developed a dual-color assay capable of identifying miRNA targeting sites in a certain gene, specifically p53, in a simple, direct, and robust manner. Results showed that p53 was a direct and critical target of miR-19b, but not miR-19a, regardless of sequence similarity. Overexpression of miR-19b observed in human cancer cells can diminish p53 protein levels and, subsequently, downstream components such as Bax and p21. This miR-19b-mediated p53 reduction was shown to promote cell cycle, cell migration or invasion, and repress senescence and apoptosis in vitro. Further investigation revealed that miR-19b controls tumor growth and metastasis in vivo. Therefore, it is possible that miR-19b antagomirs or sponges could be developed as therapeutic agents against tumor development.

MicroRNAs (miRNAs) are a group of endogenous, small noncoding RNAs of approximately 22 nucleotides in lengths. As a new class of signaling modulators, miRNAs have attracted great attention for their unique features, including multitarget regulation, tissue specificity, and evolutionary conservation. These small endogenous RNAs are able to interact with many important genes and play critical roles in a wide range of biological processes, including cell proliferation and differentiation. Strikingly, miRNAs are frequently dysregulated in human cancers. A number of studies have shown that miRNAs are involved in cancer pathogenesis by regulating oncogenes or tumor suppressor genes. Here, we review recent studies of miRNAs in cancer development and discuss their potential applications in cancer therapeutics.

Kinases become one of important groups of drug targets. To identify more kinases being potential for cancer therapy, we developed an integrative approach for the large-scale screen of functional genes capable of regulating the main traits of cancer metastasis. We first employed self-assembled cell microarray to screen functional genes that regulate cancer cell migration using a human genome kinase siRNA library. We identified 81 genes capable of significantly regulating cancer cell migration. Following with invasion assays and bio-informatics analysis, we discovered that 16 genes with differentially expression in cancer samples can regulate both cell migration and invasion, among which 10 genes have been well known to play critical roles in the cancer development. The remaining 6 genes were experimentally validated to have the capacities of regulating cell proliferation, apoptosis and anoikis activities besides cell motility. Together, these findings provide a new insight into the therapeutic use of human kinases. From the Clinical Editor This team of authors have utilized a self-assembled cell microarray to screen genes that regulate cancer cell migration using a human genome siRNA library of kinases. They validated previously known genes and identified novel ones that may serve as therapeutic targets.

Recent advances with the type II clustered regularly interspaced short palindromic repeats (CRISPR) system promise an improved approach to genome editing. However, the applicability and efficiency of this system in model organisms, such as zebrafish, are little studied. Here, we report that RNA-guided Cas9 nuclease efficiently facilitates genome editing in both mammalian cells and zebrafish embryos in a simple and robust manner. Over 35% of site-specific somatic mutations were found when specific Cas/gRNA was used to target either etsrp, gata4 or gata5 in zebrafish embryos in vivo. The Cas9/gRNA efficiently induced biallelic conversion of etsrp or gata5 in the resulting somatic cells, recapitulating their respective vessel phenotypes in etsrp(y11) mutant embryos or cardia bifida phenotypes in fau(tm236a) mutant embryos. Finally, we successfully achieved site-specific insertion of mloxP sequence induced by Cas9/gRNA system in zebrafish embryos. These results demonstrate that the Cas9/gRNA system has the potential of becoming a simple, robust and efficient reverse genetic tool for zebrafish and other model organisms. Together with other genome-engineering technologies, the Cas9 system is promising for applications in biology, agriculture, environmental studies and medicine.

MicroRNAs (miRNAs) are a group of endogenous, small noncoding RNAs of approximately 22 nucleotides in lengths. As a new class of signaling modulators, miRNAs have attracted great attention for their unique features, including multitarget regulation, tissue specificity, and evolutionary conservation. These small endogenous RNAs are able to interact with many important genes and play critical roles in a wide range of biological processes, including cell proliferation and differentiation. Strikingly, miRNAs are frequently dysregulated in human cancers. A number of studies have shown that miRNAs are involved in cancer pathogenesis by regulating oncogenes or tumor suppressor genes. Here, we review recent studies of miRNAs in cancer development and discuss their potential applications in cancer therapeutics.

MicroRNAs (miRNAs) are deregulated in human cancers. A large number of studies have shown that miRNAs play critical roles in tumorigenesis, either as oncogenes or tumor suppressors. This review provides an overview of current research on the roles of miRNA in cancer development. Furthermore, we also discuss the current progress and limitation of therapeutic application of miRNAs in preclinical studies.

miRNA globally deregulates human carcinoma. A critical open question is how many miRNAs functionally participate in cancer development, particularly in metastasis. We systematically evaluate the capability of all known human miRNAs to regulate certain metastasis-relevant cell behaviours. To perform the high-throughput screen of miRNAs, which regulate cell migration, we developed a novel self-assembled cell microarray. Here we show that over 20% of miRNAs have migratory regulation activity in diverse cell types, indicating a general involvement of miRNAs in migratory regulation. MiR-23b, which is downregulated in human colon cancer samples, potently mediates the multiple steps of metastasis, including tumour growth, invasion and angiogenesis in vivo. It regulates a cohort of prometastatic targets, including FZD7 or MAP3k1. These findings provide new insight into the physiological and potential therapeutic importance of miRNAs as a new class of functional modulators.

MicroRNAs, a group of endogenous non-coding single-strand RNAs typically of 21~23nt in length, have been convincingly shown to play a critical role in a wide variety of physiological processes such as cell proliferation, differentiation, apoptosis, tumor metastasis, etc. Here we incorporated a microfluidic device with a miRNA detection method based on ramification amplification (RAM) to increase the detection throughput and reduce the labor cost. Four different reactions could be performed in a microfluidic device: (i) reverse-transcription of miRNA, (ii) annealing of circular probe (C-Probe), (iii) C-Probe ligation, and (iv) Ramification amplification. Through monitoring the intensity of fluorescent signal, tens of miRNA can be quantified in a chip in parallel. Thus, these primary results demonstrate that this new device has advantages in throughput and cost, and it might also be used for the detection of miRNA in dangerous samples, such as virus because of its automation control system.

Recent effective use of TAL Effectors (TALEs) has provided an important approach to the design and synthesis of sequence-specific DNA-binding proteins. However, it is still a challenging task to design and manufacture effective TALE modulators because of the limited knowledge of TALE-DNA interactions. Here we synthesized more than 200 TALE modulators and identified two determining factors of transcription activity in vivo: chromatin accessibility and the distance from the transcription start site. The implementation of these modulators in a gain-of-function screen was successfully demonstrated for four cell lines in migration/invasion assays and thus has broad relevance in this field. Furthermore, a novel TALE-TALE modulator was developed to transcriptionally inhibit target genes. Together, these findings underscore the huge potential of these TALE modulators in the study of gene function, reprogramming of cellular behaviors, and even clinical investigation.

The usability of many high-throughput lab-on-a-chip devices in point-of-care applications is currently limited by the manual data acquisition and analysis process, which are labor intensive and time consuming. Based on our original design in the biochemical reactions, we proposed here a universal approach to perform automatic, fast, and robust analysis for high-throughput array-based microfluidic immunoassays. Inspired by two-dimensional (2D) barcodes, we incorporated asymmetric function patterns into a microfluidic array. These function patterns provide quantitative information on the characteristic dimensions of the microfluidic array, as well as mark its orientation and origin of coordinates. We used a computer program to perform automatic analysis for a high-throughput antigen/antibody interaction experiment in 10 s, which was more than 500 times faster than conventional manual processing. Our method is broadly applicable to many other microchannel-based immunoassays.

The chemically-synthesized siRNA duplex has become a powerful and widely used tool for RNAi loss-of-function studies, but suffers from a high off-target effect problem. Recently, endoribonulease-prepared siRNA (esiRNA) has been shown to be an attractive alternative due to its lower off-target effect and cost effectiveness. However, the current manufacturing method for esiRNA is complicated, mainly in regards to purification and normalization on a large-scale level. In this study, we present a magnetic bead-integrated chip that can immobilize amplification or transcription products on beads and accomplish transcription, digestion, normalization and purification in a robust and convenient manner. This chip is equipped to manufacture ready-to-use esiRNAs on a large-scale level. Silencing specificity and efficiency of these esiRNAs were validated at the transcriptional, translational and functional levels. Manufacture of several normalized esiRNAs in a single well, including those silencing PARP1 and BRCA1, was successfully achieved, and the esiRNAs were subsequently utilized to effectively investigate their synergistic effect on cell viability. A small esiRNA library targeting 68 tyrosine kinase genes was constructed for a loss-of-function study, and four genes were identified in regulating the migration capability of Hela cells. We believe that this approach provides a more robust and cost-effective choice for manufacturing esiRNAs than current approaches, and therefore these heterogeneous RNA strands may have utility in most intensive and extensive applications.

Endoribonuclease-prepared siRNAs (esiRNAs) have the advantages of cost effectiveness and lower off-target effects than chemically synthesized siRNA. However, the current manufacture of esiRNA is a complex process, requiring an expensive instrument and demanding skills to accomplish the transfer, purification, quantification and normalization of liquid samples. These performances significantly hamper the application of esiRNAs on a large-scale level. In this study, we present a polymer microbead-integrated chip capable of the large-scale manufacture of esiRNA in a convenient and robust manner. This chip is able to perform the amplification, transcription and enzymatic digestion of targets on polymer scaffold, thus simplifying the transfer and purification manipulation process. What is also noted, this chip can readily tailor and normalize the amount of esiRNA product by controlling the number of DNA probes and the cycle of the amplification reaction. Thus the esiRNA, also referred to as gel-esiRNA, can be immediately applied to loss-of-function study without any further treatment. The silencing specificity and efficiency of gel-esiRNAs were assessed on transcriptional, translational or cell functional levels. All data of real-time PCR, Western blot assay, or FACS clearly supported that the gel-esiRNA produced specific gene silencing as effectively as the one generated following the conventional approach. We believe that this approach would provide a more robust and cost-effective choice to manufacture esiRNAs, thus promising both more intensive and extensive applications of these heterogeneous RNA strands.

SummaryThe transcription activator-like (TAL) effector targets specific host promoter through its central DNA-binding domain, which comprises multiple tandem repeats (TALE repeats). Recent structural analyses revealed that the TALE repeats form a superhelical structure that tracks along the forward strand of the DNA duplex. Here, we demonstrate that TALE repeats specifically recognize a DNA-RNA hybrid where the DNA strand determines the binding specificity. The crystal structure of a designed TALE in complex with the DNA-RNA hybrid was determined at a resolution of 2.5 Å. Although TALE repeats are in direct contact with only the DNA strand, the phosphodiester backbone of the RNA strand is inaccessible by macromolecules such as RNases. Consistent with this observation, sequence-specific recognition of an HIV-derived DNA-RNA hybrid by an engineered TALE efficiently blocked RNase H-mediated degradation of the RNA strand. Our study broadens the utility of TALE repeats and suggests potential applications in processes involving DNA replication and retroviral infections.