Talk abstracts

Talk on Friday 01:30-01:45pm submitted by Srivats Venkataramanan

The chromatin remodeling complex SWI/SNF is a master regulator of meiotic splicing in S. cerevisiae

Srivats Venkataramanan (Department of Molecular Cell and Developmental Biology, UCLA), Stephen Douglass (Department of Molecular Cell and Developmental Biology, UCLA), Anoop Raj Galivanche (Department of Molecular Cell and Developmental Biology, UCLA), Suman K Pradhan (Department of Biochemistry, UCLA), Tracy L Johnson (Department of Molecular Cell and Developmental Biology, UCLA)

Despite its relatively streamlined genome, there are important examples of regulated RNA splicing in Saccharomyces cerevisiae. One of the most striking is the splicing of meiotic transcripts. At the onset of meiosis, Saccharomyces cerevisiae, like other eukaryotes, undergoes a dramatic reprogramming of gene expression. This includes regulated transcription and splicing of a number of meiosis-specific transcripts. Splicing of a subset of these is dependent upon the meiosis-specific splicing activator Mer1. The discovery that spliceosome assembly occurs co-transcriptionally, while RNA polymerase is engaged with the chromatin-template, raises important questions about the mechanisms by which chromatin modification influences splicing, particularly regulated splicing. Here we show a crucial role for the chromatin remodeler Swi/Snf in meiotic regulation of splicing. We find that the complex affects meiotic splicing in multiple ways. First, meiosis-specific Swi/Snf downregulation regulates downregulation of ribosomal protein genes, leading to the redistribution of spliceosomes from this abundant class of intron-containing RNAs (the RPGs) to Mer1-regulated transcripts. Secondly, expression of Mer1 itself is absolutely dependent on Swi/Snf—Snf2 is poised at the Mer1 promoter, and the timing of Snf2 downregulation allows elegant coordination of these mechanisms. Hence, the Swi/Snf complex directs the regulated splicing of meiotic genes, establishing it as a master regulator of meiotic splicing in Saccharomyces cerevisiae. Moreover, meiosis serves as an elegant example of a poorly understood, but undoubtedly important regulatory mechanism employed by cells, whereby redistribution of limiting gene-regulation machineries to different classes of targets serves as an important adaptive strategy in response to environmental and growth conditions.

Keywords: pre-mRNA splicing , Meiosis, chromatin