Project description:Post-transcriptional gene regulation relies on hundreds of RNA binding proteins (RBPs) but the function of most RBPs is unknown. The human RBP HuR/ELAVL1 is a conserved mRNA stability regulator. We used PAR-CLIP, a method based on RNA-protein crosslinking, to identify transcriptome wide ~26,000 HuR binding sites. These sites were on average highly conserved, enriched for HuR binding motifs and mainly located in 3' untranslated regions. Surprisingly, many sites were intronic, implicating HuR in splicing. Upon HuR knock down, mRNA levels and protein synthesis of thousands of target genes was down regulated, validating functionality. HuR and miRNA binding sites tended to reside nearby but generally did not overlap. Additionally, HuR knock down triggered strong and specific up regulation of miR-7. In summary, we identified thousands of direct and functional HuR targets, found a human miRNA controlled by HuR, and propose a role for HuR in splicing. PolyA mRNA was extracted from anti HuR siRNA treated and mock transfected HeLa cells to identify changes in mRNA expression and splicing. 2x100 paired end sequencing was performed according to the protocol on the Illumina HiSeq. PARCLIP was performed as in Hafner et. Al 2010 but with an antibody against endogenous HuR (3A2, Santa Cruz, sc-5261) in unstressed HeLa cells. We used, independently, 4-thiouridine (4SU) and 6-thioguanosine (6SG) to assess a possible nucleotide bias. As our proteomics measurements required labeling of cells in a special medium we also performed PAR-CLIP on cells grown in SILAC medium. Altogether we performed three PAR-CLIP experiments: 4SU labeling in standard DMEM medium, 4SU labeling in SILAC medium (as a replicate) and 6SG labeling in SILAC medium. Small RNA was extracted from anti HuR siRNA treated and mock transfected HeLa cells to identify changes in mRNA expression. Sequencing was performed on Illumina GAII using the standard sRNA 36cycle protocol.
Project description:Post-transcriptional gene regulation relies on hundreds of RNA binding proteins (RBPs) but the function of most RBPs is unknown. The human RBP HuR/ELAVL1 is a conserved mRNA stability regulator. We used PAR-CLIP, a method based on RNA-protein crosslinking, to identify transcriptome wide ~26,000 HuR binding sites. These sites were on average highly conserved, enriched for HuR binding motifs and mainly located in 3' untranslated regions. Surprisingly, many sites were intronic, implicating HuR in splicing. Upon HuR knock down, mRNA levels and protein synthesis of thousands of target genes was down regulated, validating functionality. HuR and miRNA binding sites tended to reside nearby but generally did not overlap. Additionally, HuR knock down triggered strong and specific up regulation of miR-7. In summary, we identified thousands of direct and functional HuR targets, found a human miRNA controlled by HuR, and propose a role for HuR in splicing.
Project description:We report that AUF1 modulates global mRNA stability and translation, in turn promoting the maintenance of DNA integrity. Please see individual series. In short, for AUF1 PAR-CLIP, the four isoforms of AUF1 (p37, p40, p42, and p45) tagged with a Flag epitope were expressed in HEK293 cells. For total RNA-Seq HEK293 cells were transfected with Control siRNA, AUF1 siRNA, Empty Vector, Flag-AUF1 p37, p40, p42, or p45 as well as WI-38 cells were collected at PDL 15 and 55 and also transfected with Control siRNA, AUF1 siRNA, HuR siRNA. For Ribo-Seq HeLa cells were transfected with Control siRNA, AUF1 siRNA, or HuR siRNA.
Project description:We developed a method for measuring non-specific background in PAR-CLIP data demonstrating that covalently crosslinked background binding is common, reproducible and apparently universal. Furthermore, we show that quantitative determination of background is essential for identifying targets of weakly binding RNA-binding proteins and can substantially improve motif analysis. To define background binding events in PAR-CLIP data we performed the standard PAR-CLIP protocol (Hafner et al., Cell 2010.) on lysates expressing a commonly used non-RBP control, FLAG-GFP. After FLAG-tag immunopurification of UV 365nm irradiated lysates prepared from cells supplemented with 4-thiouridine (4SU), RNA was partially digested with RNase T1, radiolabeled and separated by SDS-PAGE. Reads were sequenced by Illumina HiSeq. PAR-CLIP was also performed for HuR. Included as well is a total from lysates treated like PAR-CLIP, but without immunoprecipitation (see sample description for more detail).
Project description:Crosslinking and immunoprecipitation (CLIP) is increasingly used to map transcriptome-wide binding sites of RNA-binding proteins (RBPs). We developed a method for CLIP data analysis and applied it to compare 254 nm CLIP with PAR-CLIP, which involves crosslinking of photoreactive nucleotides with 365 nm UV light. We found small differences in the accuracy of these methods in identifying binding sites of HuR, a protein that binds low-complexity sequences and Argonaute 2, which has a complex binding specificity. We show that crosslink-induced mutations lead to single-nucleotide resolution for both PAR-CLIP and CLIP. Our results confirm the expectation from original CLIP publications that RNA-binding proteins do not protect sufficiently their sites under the denaturing conditions used during the CLIP procedure, and we show that extensive digestion with sequence-specific ribonucleases strongly biases the set of recovered binding sites. We finally show that this bias can be substantially reduced by milder nuclease digestion conditions. We performed duplicate experiments for each variant of the CLIP protocol (CLIP, PAR-CLIP), each protein (HuR, Ago2), and enzymatic digestion (complete T1 digestion, mild MNase digestion). In addition, we performed a single PAR-CLIP experiment with mild T1 digestion.
Project description:The identification of RNAs that are recognized by RNA-binding proteins (RNA-BPs) using techniques such as Crosslinking and Immunoprecipitation (CLIP) has revolutionized the genome-wide discovery of RNA-BP RNA targets. Among the different versions of CLIP that have been developed, the use of photoactivable nucleoside analogs has resulted in high efficiency photoactivable ribonucleoside-enhanced CLIP (PAR-CLIP) in vivo. Nonetheless, PAR-CLIP has not yet been applied in prokaryotes. To determine if PAR-CLIP can be used in prokaryotes, we determined suitable conditions for the incorporation of 4-thiouridine (4SU), a photoactivable nucleoside, into E. coli RNA and for the isolation of RNA crosslinked to RNA-BPs of interest. Applying this technique to Hfq, a well-characterized regulator of small RNA (sRNA)-messenger RNA (mRNA) interactions, we showed that PAR-CLIP identified most of the known sRNA targets of Hfq, as well as functionally relevant sites of Hfq-mRNA interactions at nucleotide resolution. Based on our findings, PAR-CLIP represents an improved method to identify both the RNAs and the specific regulatory sites that are recognized by RNA-BPs in prokaryotes.
Project description:We report that AUF1 modulates global mRNA stability and translation, in turn promoting the maintenance of DNA integrity. Please see individual series. In short, For AUF1 PAR-CLIP, the four isoforms of AUF1 (p37, p40, p42, and p45) tagged with a Flag epitope were expressed in HEK293 cells. For total RNA-Seq HEK293 cells were transfected with Control siRNA, AUF1 siRNA, Empty Vector, Flag-AUF1 p37, p40, p42, or p45 as well as WI-38 cells were collected at PDL 15 and 55 and also transfected with Control siRNA, AUF1 siRNA, HuR siRNA. For Ribo-Seq HeLa cells were transfected with Control siRNA, AUF1 siRNA, or HuR siRNA.
Project description:RNA-binding proteins coordinate the fates of multiple RNAs, but the principles underlying these global interactions remain poorly understood. We elucidated regulatory mechanisms of the RNA-binding protein HuR, by integrating data from diverse high-throughput targeting technologies, specifically PAR-CLIP, RIP-chip, and whole-transcript expression profiling. The number of binding sites per transcript, degree of HuR-association, and degree of HuR-dependent RNA stabilization were positively correlated. Pre-mRNA and mature mRNA containing both intronic and 3' UTR binding sites were more highly stabilized than transcripts with only 3' UTR or only intronic binding sites, suggesting that HuR couples pre-mRNA processing with mature mRNA stability. We also observed HuR-dependent splicing changes and substantial binding of HuR in poly-pyrimidine tracts of pre-mRNAs. Comparison of the spatial patterns surrounding HuR and miRNA binding sites provided functional evidence for HuR-dependent antagonism of proximal miRNA-mediated repression. We conclude that HuR coordinates gene expression outcomes at multiple interconnected steps of RNA processing. HuR (ELAVL1) PAR-CLIP
Project description:AGO-PAR-CLIP was employed to identify microRNA binding sites in BCBL-1, a Kaposi's sarcoma-associated herpesvirus (KSHV) infected B-cell line and DG75, a KSHV negative B-cell line as a control. By using our novel computational method (PARma) and differential analysis of PAR-CLIP data, highly accurate target sites of KSHV microRNAs can be defined. Examination of microRNA target sites in two different cell lines using replicate PAR-CLIP experiments