Co-regulation of splicing by Rbfox1 and hnRNP M [hnRNPM k-d+Rbfox1 RNA-Seq]

hnRNP M and Rbfox proteins are subunits of the Large Assembly of Splicing Regulators (LASR). The purpose of this study is to investigate how these two splicing factors affect each others'' role in regulating splice site choices in pre-mRNA. hnRNP M is knocked down by RNAi in Flp-In T-REx 293 cells (Invitrogen), whereas Rbfox1 is expressed inducibly under tetracycline control from construct integrated into the genome at the FRT site. Using this system, splicing and expression profiles of cells expressing and/or lacking these proteins are compared on a whole genome level by RNA-seq technology. Overall design: The experiment was performed in Flp-In T-REx 293, Rbfox2 knockout cells (clone 7), in which the Rbfox2 ORF was disrupted in the first constitutive exon (exon 3), thus these cells do not produce endogenous Rbfox protein. In addition to this, cells expressing Flag-tagged Rbfox1 under tetracycline control from a pcDNA5/FRT/TO construct inserted into the FRT site were generated. hnRNP M was knocked down to 10% of the normal levels by transient expression of two RNA hairpins targeting separate 3'' UTR regions. A non-targeting hairpin served as control. Four separate cell populations: not expressing Rbfox with normal levels fo hnRNP M; expressing Rbfox1 with normal hnRNP M levels; not expressing Rbfox, hnRNP M expression reduced by 90%; expressing Rbfox1, hnRNP M reduced by 90% were each grown independently in triplicates. Total RNA was collected from these cells and further treated with DNase I to avoid DNA contamination. Illumina TruSeq stranded mRNA kit was used to generate strand-specific libraries. These libraries were subjected to 50bp paired-end sequencing (Illumina HiSeq2000 platform). In parallel, a fraction of each cell population was lysed in RIPA buffer for protein analysis.

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Damianov A, Ying Y, Lin CH, Lee JA, Tran D, Vashisht AA, Bahrami-Samani E, Xing Y, Martin KC, Wohlschlegel JA, Black DL