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:This experiment sought to determine the genome-wide interactome of CTCF in human cells. PAR-CLIP seq for CTCF was performed in U2OS cells in 2 biological replicates
Project description:The conserved human LIN28 RNA-binding proteins function in development, maintenance of pluripotency and oncogenesis. We used PAR-CLIP and a newly developed variant of this method, iDo-PAR-CLIP, to identify LIN28B targets as well as sites bound by the individual RNA binding domains of LIN28B in the human transcriptome at nucleotide resolution. The position of target binding sites reflected the known structural relative orientation of individual LIN28B binding domains, validating iDo-PAR-CLIP. Our data suggest that LIN28B directly interacts with most expressed mRNAs and members of the let-7 microRNA family. The Lin28 binding motif detected in pre-let-7 was enriched in mRNA sequences bound by LIN28B. Upon LIN28B knock down, cell proliferation and the cell cycle were strongly impaired. Quantitative shotgun proteomics of LIN28B depleted cells revealed significant reduction of protein synthesis from its RNA targets that function in translation, mRNA splicing and cell cycle control. Computational analyses provided evidence that the strength of protein synthesis reduction correlated with the location of LIN28B binding sites within target transcripts. We used PAR-CLIP and a newly developed variant of this method, iDo-PAR-CLIP, to identify LIN28B targets as well as sites bound by the individual RNA binding domains of LIN28B in the human transcriptome at nucleotide resolution.
Project description:Protein-RNA interactions are integral components of nearly every aspect of biology including regulation of gene expression, assembly of cellular architectures, and pathogenesis of human diseases. However, studies in the past few decades have only uncovered a small fraction of the vast landscape of the protein-RNA interactome in any organism, and even less is known about the dynamics of protein-RNA interactions under changing developmental and environmental conditions. Here, we describe the gPAR-CLIP (global photoactivatable-ribonucleoside-enhanced crosslinking and immunopurification) approach for capturing regions of the transcriptome bound by RNA-binding proteins (RBPs) in budding yeast. We report over 13,000 RBP crosslinking sites in untranslated regions (UTR) covering 72% of protein-coding transcripts encoded in the genome, confirming 3M-bM-^@M-^Y UTRs as major sites for RBP interaction. Comparative genomic analyses reveal that RBP crosslinking sites are highly conserved, and RNA folding predictions indicate that secondary structural elements are constrained by protein binding and may serve as generalizable modes of RNA recognition. Finally, 38% of 3M-bM-^@M-^Y UTR crosslinking sites show changes in RBP occupancy upon glucose or nitrogen deprivation, with major impacts on metabolic pathways as well as mitochondrial and ribosomal gene expression. Our study offers an unprecedented view of the pervasiveness and dynamics of protein-RNA interactions in vivo. Duplicate gPAR-CLIP and mRNA-seq libraries were sequenced from yeast strains for each of three conditions: log-phase growth, growth after 2 hour glucose starvation, and growth after 2 hour nitrogen starvation. Additional duplicate mRNA-seq libraries were sequenced from yeast strains grown in the absence of 4-thiouracil. gPAR-CLIP libraries were used to determine regions of mRNA bound by proteins. mRNA-seq libraries served as controls for mRNA abundance. A Puf3p PAR-CLIP library was sequenced to determine how well gPAR-CLIP captured the binding signatures of a single RNA-binding protein.