Project description:Small RNAs regulate the genetic networks through a ribonucleoprotein complex called the RNA induced silencing complexes (RISC), which in mammals contains at its center one of four Argonaute proteins (Ago1-4). A key regulatory event in the RNAi and miRNA pathways is Ago loading, where double stranded small RNA duplexes are incorporated into RISC (pre-RISC) and then become single stranded (mature-RISC), a process that is not well understood. The Agos contain an evolutionary conserved PAZ (Piwi/Argonaute/Zwille) domain whose primary function is to bind the 3’-end of small RNAs. We created multiple Paz domain disrupted Ago mutant proteins and studied their biochemical properties and biological functionality in cells. We found that the Paz domain is dispensable for Ago loading of slicing-competent RISC. In contrast, in the absence of slicer activity or slicer substrate duplex RNAs, Paz-disrupted Agos bound duplex siRNAs but were unable to unwind/eject the passenger strand and form functional RISC complexes. We have discovered that the highly conserved Paz domain plays an important role in RISC activation, providing new mechanistic insights into how miRNAs regulate genes, as well as new insights for future design of miRNA and RNAi-based therapeutics. Various Argonautes associated small RNA profiles were generated by deep sequencing the Agos-IP samples in HEK293 Cells transfected with corresponding Argonaute.
Project description:Small RNAs regulate the genetic networks through a ribonucleoprotein complex called the RNA induced silencing complexes (RISC), which in mammals contains at its center one of four Argonaute proteins (Ago1-4). A key regulatory event in the RNAi and miRNA pathways is Ago loading, where double stranded small RNA duplexes are incorporated into RISC (pre-RISC) and then become single stranded (mature-RISC), a process that is not well understood. The Agos contain an evolutionary conserved PAZ (Piwi/Argonaute/Zwille) domain whose primary function is to bind the 3’-end of small RNAs. We created multiple Paz domain disrupted Ago mutant proteins and studied their biochemical properties and biological functionality in cells. We found that the Paz domain is dispensable for Ago loading of slicing-competent RISC. In contrast, in the absence of slicer activity or slicer substrate duplex RNAs, Paz-disrupted Agos bound duplex siRNAs but were unable to unwind/eject the passenger strand and form functional RISC complexes. We have discovered that the highly conserved Paz domain plays an important role in RISC activation, providing new mechanistic insights into how miRNAs regulate genes, as well as new insights for future design of miRNA and RNAi-based therapeutics.
Project description:Argonaute proteins lie at the heart of the RNA-Induced Silencing Complex (RISC), wherein they use small RNA guides to recognize targets. Some Argonaute proteins can directly cleave their targets, whereas others recruit co-factors to repress independently of “slicing.” Prior studies established the architecture of Argonaute proteins; however, we have not yet had a detailed picture of an Argonaute whose biochemical and biological functions were well established. Here we describe the crystal structure of human Argonaute-2 bound to miR-20a at 2.2 Å resolution. Overall architecture and domain organization is shared with its prokaryotic counterparts, though Ago2 is somewhat more open, with its PAZ domain further removed from the other domains. The miRNA is anchored at both ends by the Mid and PAZ domains but makes several kinks and turns along the binding groove. The RNA confers remarkable stability on the Argonaute protein, locking this otherwise flexible enzyme into a stable conformation. total small RNAs (19-29nt) and small RNAs associated with purified hArgonaute2 purified from SF9 cells. These were processed and sequenced on Illumina GA-II platform.
Project description:Argonaute proteins lie at the heart of the RNA-Induced Silencing Complex (RISC), wherein they use small RNA guides to recognize targets. Some Argonaute proteins can directly cleave their targets, whereas others recruit co-factors to repress independently of “slicing.” Prior studies established the architecture of Argonaute proteins; however, we have not yet had a detailed picture of an Argonaute whose biochemical and biological functions were well established. Here we describe the crystal structure of human Argonaute-2 bound to miR-20a at 2.2 Å resolution. Overall architecture and domain organization is shared with its prokaryotic counterparts, though Ago2 is somewhat more open, with its PAZ domain further removed from the other domains. The miRNA is anchored at both ends by the Mid and PAZ domains but makes several kinks and turns along the binding groove. The RNA confers remarkable stability on the Argonaute protein, locking this otherwise flexible enzyme into a stable conformation.
Project description:We have sequenced miRNA libraries from human embryonic, neural and foetal mesenchymal stem cells. We report that the majority of miRNA genes encode mature isomers that vary in size by one or more bases at the 3’ and/or 5’ end of the miRNA. Northern blotting for individual miRNAs showed that the proportions of isomiRs expressed by a single miRNA gene often differ between cell and tissue types. IsomiRs were readily co-immunoprecipitated with Argonaute proteins in vivo and were active in luciferase assays, indicating that they are functional. Bioinformatics analysis predicts substantial differences in targeting between miRNAs with minor 5’ differences and in support of this we report that a 5’ isomiR-9-1 gained the ability to inhibit the expression of DNMT3B and NCAM2 but lost the ability to inhibit CDH1 in vitro. This result was confirmed by the use of isomiR-specific sponges. Our analysis of the miRGator database indicates that a small percentage of human miRNA genes express isomiRs as the dominant transcript in certain cell types and analysis of miRBase shows that 5’ isomiRs have replaced canonical miRNAs many times during evolution. This strongly indicates that isomiRs are of functional importance and have contributed to the evolution of miRNA genes
Project description:We have sequenced miRNA libraries from human embryonic, neural and foetal mesenchymal stem cells. We report that the majority of miRNA genes encode mature isomers that vary in size by one or more bases at the 3’ and/or 5’ end of the miRNA. Northern blotting for individual miRNAs showed that the proportions of isomiRs expressed by a single miRNA gene often differ between cell and tissue types. IsomiRs were readily co-immunoprecipitated with Argonaute proteins in vivo and were active in luciferase assays, indicating that they are functional. Bioinformatics analysis predicts substantial differences in targeting between miRNAs with minor 5’ differences and in support of this we report that a 5’ isomiR-9-1 gained the ability to inhibit the expression of DNMT3B and NCAM2 but lost the ability to inhibit CDH1 in vitro. This result was confirmed by the use of isomiR-specific sponges. Our analysis of the miRGator database indicates that a small percentage of human miRNA genes express isomiRs as the dominant transcript in certain cell types and analysis of miRBase shows that 5’ isomiRs have replaced canonical miRNAs many times during evolution. This strongly indicates that isomiRs are of functional importance and have contributed to the evolution of miRNA genes Sequence library of miRNAs from a single sample of human foetal mesenchymal stem cells. Results tested and confirmed by northern blotting. Please note that only raw data files are available for the embryonic and neual samples and thus, directly submitted to SRA (SRX547311, SRX548700, respectively under SRP042115/PRJNA247767)