Project description:This experiment identifies hnRNP A1 binding sites transcriptome-wide in Hela cells. HeLa cells with inducible expression of T7-tagged hnRNP A1 were grown to approximately 90% confluence and then subject to iCLIP analysis (following the protocol from Huppertz et al. 2014 (iCLIP: protein-RNA interactions at nucleotide resolution)). The iCLIP library was sequenced using Illumina's HighSeq 1500
Project description:The scaffold attachment factors SAFB1 and SAFB2 are paralogs, which are involved in cell cycle regulation, apoptosis, differentiation, and stress response. They have been shown to function as estrogen receptor co-repressors, and there is evidence for a role in breast tumorigenesis. To identify their endogenous target genes in MCF-7 breast cancer cells, we utilized gene expression array analysis, which was set up in a two-by-four design, with vehicle and estrogen treatment, and control, SAFB1, SAFB2, and SAFB1/SAFB2 siRNA as variables. Using custom chips containing 1.5 kb upstream regulatory region, we identified 541 SAFB1/SAFB2 binding sites in promoters of known genes, with significant enrichment on chromosome 1 and 6. Gene expression analysis revealed that the majority of target genes were induced in the absence of SAFB1 or SAFB2, and less were repressed. In contrast to SAFB2, which shared most of its target genes with SAFB1, SAFB1 had many unique target genes, most of them involved in regulation of the immune system. A subsequent analysis of the estrogen treatment group revealed that twelve percent of estrogen-regulated genes were dependent on SAFB1, with the majority being estrogen-repressed genes. These were primarily genes involved in apoptosis, such as BBC3, NEDD9, and OPG. Thus, this study confirms SAFB1/SAFB2âs primary role as co-repressors, and also uncovers a previously unknown role for SAFB1 in regulation of immune genes, and in estrogen-mediated repression of genes. To identify transcripts which were altered upon decrease of SAFB1 or SAFB2 expression we performed gene expression array analysis in MCF-7 cells. A secondary goal was to identify ERα-target genes for which estrogen regulation was dependent upon SAFB expression. We also added an experimental group in which we co-transfected siRNAs targeting both SAFB1 and SAFB2, which allowed us to address the question of interactions between the two paralogs. We therefore set up an experiment reflecting a 2x4 design, with a total of eight experimental groups.
Project description:A key function for RNA-binding proteins in orchestrating plant development and environmental responses is well established. However, the lack of a genome-wide view on their in vivo binding targets and binding landscapes represents a gap in understanding the mode of action of plant RNA-binding proteins. Here, we adapt individual nucleotide resolution crosslinking immunoprecipitation (iCLIP) for genome-wide determining the binding repertoire of the circadian clock-regulated Arabidopsis thaliana glycine-rich RNA-binding protein AtGRP7. We have established iCLIP for plants to identify target transcripts of the RNA-binding protein AtGRP7. This paves the way to investigate the dynamics of posttranscriptional networks in response to exogenous and endogenous cues.
Project description:iCLIP experiment to assess the binding of the highly abundant nuclear RNA-binding protein hnRNP C and core splicing factor U2AF65 on a genomic scale. To investigate how both proteins compete for binding at a subset of sites, U2AF65 iCLIP experiments were performed from both HNRNPC knockdown and control HeLa cells.
Project description:The studies of spliceosomal interactions are challenging due to their dynamic nature. Here we developed spliceosome iCLIP, which immunoprecipitates SmB along with snRNPs and auxiliary RNA binding proteins (RBPs) to simultaneously map the spliceosomal binding to human snRNAs and pre-mRNAs. This identified 9 distinct regions on pre-mRNAs, which overlap with position-dependent binding patterns of 15 RBPs. Using spliceosome iCLIP, we additionally identified >50,000 branchpoints (BPs) that have canonical features, unlike those identified by RNA-seq. The iCLIP BPs generally overlap with the computationally predicted BPs, and alternative BPs are associated with extended regions of structurally accessible RNA. We find that the position and strength of BPs defines the binding patterns of SF3 and U2AF complexes, whereas the RNA structure around BPs affects the sensitivity of exons to perturbation of these complexes. Our findings introduce spliceosome iCLIP as a new method for transcriptomic studies of BPs and splicing mechanisms.
Project description:This experiments was performed in HeLa cells according to the iCLIP protocol with the following modifications: no antiRNase was used and the concentration of RNase I was 0.5 U/ml. In iCLIP4, the dephosphorylation step was omitted from the standard protocol. The rest of the protocol was identical to the previously published iCLIP protocol )Huppertz I, Attig J, D'Ambrogio A, Easton LE, Sibley CR, Sugimoto Y, Tajnik M, Knig J, Ule J: iCLIP: protein-RNA interactions at nucleotide resolution. Methods 2014, 65:274-287).
Project description:Oxygen deprivation (hypoxia) is encountered in physiological conditions but also characterizes many pathological conditions including ischemia and cancer. In order to survive, the cells usually rely upon the activation of the Hypoxia Inducible Factors (HIF), a small family of heterodimeric transcriptional activators. However, adaption to hypoxia also involves, lesser-known, HIF-independent processes that affect chromatin remodelling and nuclear architecture. SAFB1/2 (Scaffold Attachment Factors B1 and 2) are integral components of the nuclear matrix of vertebrate cells and known to affect functions that include transcriptional regulation, RNA processing and response to DNA damage. Our work indicates that SAFB1/2 swiftly change their localization from the insoluble matrix fraction to more soluble nuclear fractions in a HIF-independent manner. To extend our study, we performed immunoprecipitation experiments with SAFB1 or SAFB2 from cells exposed to both normoxia and short-term hypoxia (2 hours). Mass spectrometry analysis of the immunoprecipitates revealed that short-term exposure of cells to low oxygen levels alters the protein-protein interactions of SAFB1/2 mainly with proteins implicated in mRNA maturation and transcriptional control. Our data suggest that SAFB1/2 proteins participate in molecular mechanisms immediately responsive to hypoxia that entail their rapid mobilization from the nuclear matrix and their altered association with constituents of splicing and transcriptional machinery.
Project description:The scaffold attachment factors SAFB1 and SAFB2 are paralogs, which are involved in cell cycle regulation, apoptosis, differentiation, and stress response. They have been shown to function as estrogen receptor co-repressors, and there is evidence for a role in breast tumorigenesis. To identify their endogenous target genes in MCF-7 breast cancer cells, we utilized gene expression array analysis, which was set up in a two-by-four design, with vehicle and estrogen treatment, and control, SAFB1, SAFB2, and SAFB1/SAFB2 siRNA as variables. Using custom chips containing 1.5 kb upstream regulatory region, we identified 541 SAFB1/SAFB2 binding sites in promoters of known genes, with significant enrichment on chromosome 1 and 6. Gene expression analysis revealed that the majority of target genes were induced in the absence of SAFB1 or SAFB2, and less were repressed. In contrast to SAFB2, which shared most of its target genes with SAFB1, SAFB1 had many unique target genes, most of them involved in regulation of the immune system. A subsequent analysis of the estrogen treatment group revealed that twelve percent of estrogen-regulated genes were dependent on SAFB1, with the majority being estrogen-repressed genes. These were primarily genes involved in apoptosis, such as BBC3, NEDD9, and OPG. Thus, this study confirms SAFB1/SAFB2’s primary role as co-repressors, and also uncovers a previously unknown role for SAFB1 in regulation of immune genes, and in estrogen-mediated repression of genes.