Poster abstracts
Poster number 52 submitted by A. Elizabeth Hildreth
Identifying the regulatory role of chromatin in transcription termination
A. Elizabeth Hildreth (Department of Biological Sciences, University of Pittsburgh), Karen M. Arndt, PhD (Department of Biological Sciences, University of Pittsburgh)
Abstract:
Normal cellular growth and development relies on the precise regulation of gene expression. In eukaryotes, the chromatin template acts as a barrier to the transcription machinery. Chromatin consists of nucleosomes, which contain approximately 147 basepairs of DNA surrounding an octamer of histone proteins H2A, H2B, H3, and H4. To faithfully express the genetic material, a host of transcription factors regulate RNA polymerase II activity during transcription initiation, elongation, and termination. The Nrd1-Nab3-Sen1 (NNS) complex regulates transcription termination of many short noncoding RNAs, some short protein-coding RNAs, and intergenic transcripts in yeast. Despite a few studies showing that transcription-coupled histone modifications are important for proper termination, very little is known about the role of chromatin in this pathway. The goal of my project is to elucidate how chromatin influences transcription termination using the NNS pathway in Saccharomyces cerevisiae as a model. To screen for histone residues required for termination by the NNS pathway, I have made use of a plasmid library encoding histones with all possible alanine substitutions and a well-characterized termination reporter. I have identified 10 residues in H3 and H4 with defects in termination, and have begun functionally characterizing their transcription-related phenotypes. Analysis to this point reveals that these amino acid substitutions in the histones cause widely varying phenotypes, perhaps suggesting that these residues promote NNS-dependent termination in different ways. Future work will elucidate the mechanisms by which these histone residues regulate proper transcription termination.
Keywords: chromatin, transcription, S cerevisiae