Talk abstracts

Talk on Friday 05:15-05:30pm submitted by Hualin Zhou

The Role of Hu Proteins in The Coupling of Transcription and Splicing

Hua-Lin Zhou (Genetics Department, Case Western Reserve University), Hua Lou (Genetics Department, Case Western Reserve University)

Abstract:
Rapid progress in recent years has demonstrated that splicing is tightly coupled to transcription and this coupling provides a possibility that elongation rate of RNAPII can influence splice site selection. While modification of chromatin structure has been shown to regulate splice site choice through affecting transcription elongation rate, no splicing regulators had been shown to directly interact with chromosomal proteins to regulate the transcription elongation rate.
Hu proteins are a family (HuA/R, HuB, HuC and HuD) of mammalian RNA-binding proteins. Our previously studies demonstrated that Hu proteins function as important splicing regulators, which inhibits exon 23a of the neurobromatosis type I (NF1) pre-mRNA inclusion by binding to AU-rich sequences surrounding this exon. In this report, we will discuss a potential novel role of Hu proteins in alternative splicing regulation through affecting transcription elongation rate.
Through a yeast two-hybrid screen, we identified histone deacetylase 2 (HDAC2) as proteins that directly interact with HuC protein. These interactions were then verified in mammalian cells. The interactions between HuC and chromatin-associated proteins prompted us to postulate a role of this protein in transcription. Co-immunoprecipitation assay indicates that Hu proteins interact with both ser5 and ser2 phosphorylated RNAPII in an RNA-independent fashion. An interaction between a transcription elongation factor CDK9 and Hu proteins was also detected. There results suggest that Hu proteins play a role in coupling transcription and splicing.
The ChIP assay also demonstrates that the acetylation level of both histone H3 and H4 at the exon 23a region is much higher in high Hu expressing CA77 cells than low Hu expressing HeLa cells. These results help us to develop a working model that Hu proteins increase transcription elongation rate through modulating the local chromatin structure surrounding exon 23a via its interactions with histones and/or HDAC2. Our studies uncover a novel regulatory mechanism of alternative splicing by Hu proteins. Additional experiments that will provide more mechanistic details will be discussed.
HU

Keywords: Hu proteins, Alternative splicing