Project description:QKI is required for myelin formation in the verterbrate brain. It functions by binding RNA and regulating its stability, translation, and/or aternative splicing. We have used Affymetrix exon arrays to assess changes in gene expression in response to QKI knockdown on an exon level in rat CG-4 oligodendrocyte precursor cells. Knockdown cells were compared to control cells. Knockdown groups included QKI siRNA transfection, QKI shRNA stable transfection, and hnRNP A1 transient transfection. Control groups consisted of untransfected, control siRNA transfection, control shRNA stable transfection. Each group was analyzed in triplicate.
Project description:poly(A)+ RNA samples from hnRNP C siRNA knockdown and control HeLa cells were compared on a splice-junction microarray to detect changes in alternative splicing. Using the ASPIRE3 algorithm, we detected changes in splicing at 1,340 alternative exons. We observed a similar incidence of increased or decreased exon inclusion in hnRNP C knockdown cells, indicating that hnRNP C can either silence or enhance exon inclusion, respectively. We validated changes at 26 exons by RT-PCR with a 92% success rate.
Project description:Mediator complex is an integrative hub for transcriptional regulation. Here we show that Mediator regulates alternative mRNA processing via its Med23 subunit. Combining tandem affinity purification and mass spectrometry, we identified a number of mRNA processing factors that bind to a soluble recombinant Mediator subunit MED23 but not to several other Mediator components. One of these factors, hnRNP L, specifically interacts with MED23 in vitro and in vivo. Consistently, Mediator partially colocalizes with hnRNP L and the splicing machinery in the cell. Functionally Med23 regulates a subset of hnRNP L-targeted alternative splicing (AS) and alternative cleavage and polyadenylation (APA) events as shown by minigene reporters and exon array analysis. ChIP-seq analysis revealed that Med23 can regulate hnRNP L occupancy at their co-regulated genes. Taken together, these results demonstrate a crosstalk between Mediator and the splicing machinery, suggesting a novel mechanism for coupling mRNA processing to transcription. We performed an exon array experiment using HeLa cells expressing Med23, hnRNP L or control siRNAs which were established by a virus-mediated siRNA technology. Each sample was done in three biological replicates. Total RNA of these cell lines was processed and hybridized to the Affymetrix human exon array.