Project description:Rationale: RNA binding protein Apobec1 Complementation Factor (A1CF) regulates posttranscriptional ApoB mRNA editing but the range of RNA targets and long-term impact of altered A1CF expression on liver function are unknown. Objective: We studied hepatocyte-specific A1cf transgenic (A1cf +/Tg), A1cf+/Tg Apobec1– /– and A1cf –/– mice fed chow or high fat/high fructose diets using RNA-Seq, RNA-CLIP Seq and tissue microarrays from human hepatocellular cancer (HCC). Findings: A1cf +/Tg mice exhibited increased hepatic proliferation and steatosis, with increased lipogenic gene expression (Mogat1, Mogat2, Cidea, Cd36) associated with shifts in polysomal RNA distribution. Aged A1cf +/Tg mice developed spontaneous fibrosis, dysplasia and HCC, which was accelerated on a high fat/fructose diet and independent of Apobec1. RNA-Seq revealed increased expression of mRNAs involved in oxidative stress (Gstm3, Gpx3, Cbr3), inflammatory response (Il19, Cxcl14, Tnfα, Ly6c), extracellular matrix organization (Mmp2, Col1a1, Col4a1), proliferation (Kif20a, Mcm2, Mcm4, Mcm6) with a subset of mRNAs (including Sox4, Sox9, Cdh1) identified in RNA CLIP-Seq. Increased A1CF expression in human HCC correlated with advanced fibrosis and with reduced survival in a subset with nonalcoholic fatty liver disease. Conclusions: Hepatic A1CF overexpression selectively alters polysomal distribution and mRNA expression, promoting lipogenic, proliferative and inflammatory pathways leading to HCC.
Project description:Rationale: RNA binding protein Apobec1 Complementation Factor (A1CF) regulates posttranscriptional ApoB mRNA editing but the range of RNA targets and long-term impact of altered A1CF expression on liver function are unknown. Objective: We studied hepatocyte-specific A1cf transgenic (A1cf +/Tg), A1cf+/Tg Apobec1– /– and A1cf –/– mice fed chow or high fat/high fructose diets using RNA-Seq, RNA-CLIP Seq and tissue microarrays from human hepatocellular cancer (HCC). Findings: A1cf +/Tg mice exhibited increased hepatic proliferation and steatosis, with increased lipogenic gene expression (Mogat1, Mogat2, Cidea, Cd36) associated with shifts in polysomal RNA distribution. Aged A1cf +/Tg mice developed spontaneous fibrosis, dysplasia and HCC, which was accelerated on a high fat/fructose diet and independent of Apobec1. RNA-Seq revealed increased expression of mRNAs involved in oxidative stress (Gstm3, Gpx3, Cbr3), inflammatory response (Il19, Cxcl14, Tnfα, Ly6c), extracellular matrix organization (Mmp2, Col1a1, Col4a1), proliferation (Kif20a, Mcm2, Mcm4, Mcm6) with a subset of mRNAs (including Sox4, Sox9, Cdh1) identified in RNA CLIP-Seq. Increased A1CF expression in human HCC correlated with advanced fibrosis and with reduced survival in a subset with nonalcoholic fatty liver disease. Conclusions: Hepatic A1CF overexpression selectively alters polysomal distribution and mRNA expression, promoting lipogenic, proliferative and inflammatory pathways leading to HCC.
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 SuperSeries is composed of the following subset Series: GSE21574: Transcriptome-wide identification of RNA-binding protein and microRNA target sites by PAR-CLIP: QKI data GSE21575: Transcriptome-wide identification of RNA-binding protein and microRNA target sites by PAR-CLIP: IGF2BP data GSE21577: Transcriptome-wide identification of RNA-binding protein and microRNA target sites by PAR-CLIP: miRNA inhibition data GSE21918: Transcriptome-wide identification of RNA-binding protein and microRNA target sites by PAR-CLIP: sequencing data Refer to individual Series
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.
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: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: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