Project description:In this study, an exoribonuclease was analyzed by iCLIP. The data documents the role of the archaeal exosome as an exoribonuclease and RNA-tailing enzyme interacting with all RNA classes. Mapping of most reads to mRNAs underlines the role of exosome in mRNA turnover, which is important for adaptation of prokaryotic cells to changing environmental conditions. The clustering of crosslink sites near 5’-ends of genes suggests simultaneous binding of both RNA ends by the S. solfataricus exosome. This may serve to prevent translation of mRNAs designated to degradation in 3’-5’ direction.
Project description:In this study, an exoribonuclease was analyzed by iCLIP. The data documents the role of the archaeal exosome as an exoribonuclease and RNA-tailing enzyme interacting with all RNA classes. Mapping of most reads to mRNAs underlines the role of exosome in mRNA turnover, which is important for adaptation of prokaryotic cells to changing environmental conditions. The clustering of crosslink sites near 5’-ends of genes suggests simultaneous binding of both RNA ends by the S. solfataricus exosome. This may serve to prevent translation of mRNAs designated to degradation in 3’-5’ direction.
Project description:BACKGROUND:The archaeal exosome is an exoribonucleolytic multiprotein complex, which degrades single-stranded RNA in 3' to 5' direction phosphorolytically. In a reverse reaction, it can add A-rich tails to the 3'-end of RNA. The catalytic center of the exosome is in the aRrp41 subunit of its hexameric core. Its RNA-binding subunits aRrp4 and aDnaG confer poly(A) preference to the complex. The archaeal exosome was intensely characterized in vitro, but still little is known about its interaction with natural substrates in the cell, particularly because analysis of the transcriptome-wide interaction of an exoribonuclease with RNA is challenging. RESULTS:To determine binding sites of the exosome to RNA on a global scale, we performed individual-nucleotide resolution UV crosslinking and immunoprecipitation (iCLIP) analysis with antibodies directed against aRrp4 and aRrp41 of the chrenarchaeon Sulfolobus solfataricus. A relatively high proportion (17-19%) of the obtained cDNA reads could not be mapped to the genome. Instead, they corresponded to adenine-rich RNA tails, which are post-transcriptionally synthesized by the exosome, and to circular RNAs (circRNAs). We identified novel circRNAs corresponding to 5' parts of two homologous, transposase-related mRNAs. To detect preferred substrates of the exosome, the iCLIP reads were compared to the transcript abundance using RNA-Seq data. Among the strongly enriched exosome substrates were RNAs antisense to tRNAs, overlapping 3'-UTRs and RNAs containing poly(A) stretches. The majority of the read counts and crosslink sites mapped in mRNAs. Furthermore, unexpected crosslink sites clustering at 5'-ends of RNAs was detected. CONCLUSIONS:In this study, RNA targets of an exoribonuclease were analyzed by iCLIP. The data documents the role of the archaeal exosome as an exoribonuclease and RNA-tailing enzyme interacting with all RNA classes, and underlines its role in mRNA turnover, which is important for adaptation of prokaryotic cells to changing environmental conditions. The clustering of crosslink sites near 5'-ends of genes suggests simultaneous binding of both RNA ends by the S. solfataricus exosome. This may serve to prevent translation of mRNAs dedicated to degradation in 3'-5' direction.
Project description:blan08_rnapaths; Analyses of endogenous rna substrates of xrn and exosome and ptgs pathways What are the endogenous RNA substrates co-regulated by RQC and PTGS pathways? Genome-wide analyses of endogenous RNA substrates of RNA Quality Control pathways; wild type versus 15 mutants. 30 dye-swap - gene knock in (transgenic), gene knock out
Project description:blan08_rnapaths; Analyses of endogenous rna substrates of xrn and exosome and ptgs pathways What are the endogenous RNA substrates co-regulated by RQC and PTGS pathways? Genome-wide analyses of endogenous RNA substrates of RNA Quality Control pathways; wild type versus 15 mutants.
Project description:The exosome complex plays a central role in RNA metabolism, and each of its core subunits is essential for viability in yeast However, comprehensive studies of exosome substrates and functional analyses of its subunits in multi.CELlular eukaryotes are lacking Here we show that, in sharp contrast to yeast and metazoan exosome complexes, individual subunits of the plant exosome core are functionally specialized Using whole-genome oligonucleotide tiling microarray analyses of csl4 null mutant plants and conditional genetic depletions of RRP4 and RRP41, we uncovered unexpected functional plasticity in the plant exosome core as well as generated a set of high-resolution genome-wide maps of Arabidopsis exosome targets These analyses provide evidence for widespread polyadenylation- and exosome-mediated RNA quality control in plants and reveal novel aspects of stable structural RNA metabolism Finally, numerous novel exosome substrates were discovered, including a select subset of mRNAs, miRNA processing intermediates, and hundreds of noncoding RNAs, the vast majority of which have not been previously described This large collection of RNAs belong to a Òdeeply hiddenÓ layer of the transcriptome that is tightly repressed and can only be visualized upon inhibition of exosome activity These first genome-wide maps of exosome substrates will aid in illuminating new fundamental components and regulatory mechanisms of eukaryotic transcriptomes Keywords: Strand-specific gene expression analysis using whole-genome oligonucleotide tiling microarray analyses of three exosome subunits, using csl4 null mutant plants and conditional genetic depletions of RRP4 and RRP41.
Project description:The RNA exosome complex functions in both the accurate processing and rapid degradation of many different classes of RNA. Functional and structural analyses indicate that RNA can either be threaded through the central channel of the exosome or more directly access the active sites of the ribonucleases Rrp44 and Rrp6, but it was unclear how many substrates follow each pathway in vivo. To address this we used UV crosslinking in growing cells to identify transcriptome-wide interactions of RNAs with the major nuclear exosome-cofactor Mtr4 and with individual exosome subunits (Rrp6, Csl4, Rrp41 and Rrp44) along the threaded RNA path. We performed comparative analyses on exosome complexes lacking the exonucleolytic activity of Rrp44, either carrying a mutation in the Rrp44 S1 RNA-binding domain, predicted to disfavor direct access to the Rrp44 exonuclease active site, or with multiple mutations in Rrp41, reported to block RNA passage through the central channel. Our analysis identified targets using preferentially channel-threading pathway such as mRNAs, 5S rRNA or scR1. Our results suggest as well that aborted tRNAs transcripts, released during transcription, would be rapidly degraded using this route. Alternatively, pre-tRNAs appears to access Rrp44 directly. Both routes seems to be involved for degradation or maturation of RNAPI transcripts. The Rrp41 mutations were found to block substrate passage to Rrp44 only for cytoplasmic mRNAs, apparently confirming the prediction of widening of the lumen in the nuclear, Rrp6-associated complex.