Organization of protein factors on the carboxy terminal domain of RNA polymerase II in yeast (941.1)

Abstract

Organization of Protein Factors on the Carboxy Terminal Domain of RNA Polymerase II in Yeast Mohammad M. Mosaheb and Stephen M. Fuchs: Tufts University, Medford, MA, Department of Biology.The Carboxy Terminal Domain (CTD) of RNA Polymerase II (RNAPII) in yeast is made up of 26 heptad repeats with the sequence YSPTSPS. The heptad repeats have different phosphorylation patterns at their 3 serines at different stages of transcription which mediate the recruitment of specific protein factors required for transcription. Our goal is to find out how the protein factors organize themselves on the 26 repeats ‐ Do the protein factors have to bind to a specific range of repeats? Or can they bind anywhere on the CTD and still be functional. For this work, we divided the CTD into 3 segments of 8 heptad repeats and subsequently created variants in which the serines in one of three segments were replaced with alanine. Measuring yeast growth on plates we have demonstrated that repeats likely have non‐redundant function. We are currently isolating RNAPII complexes to biochemically identify difference in protein factor abundance in our three mutants. We are also creating 3 new mutants heptad repeats each one with only one of the 3 serines mutated, these new mutants will be helpful to decipher which one of the 3 serines is more important in recruiting our protein factor of interest.