Poster abstracts
Poster number 20 submitted by Victor Corral
A phosphorylation circuitry of RNaseH1 regulates R-loop homeostasis
Victor Corral (Pharmacology, University of Minnesota - Twin Cities), Hai D. Nguyen (Pharmacology, University of Minnesota - Twin Cities), Maxwell Bannister (Undergraduate studies, Augsburg University)
Abstract:
R-loop is a transcription intermediate resulting from the formation of stable RNA:DNA hybrids and a displaced single-stranded DNA (ssDNA). Aberrant accumulation or distribution of R-loops in the genome, if not regulated, becomes a source of genomic instability, a hallmark in many cancers. Our lab previously found that the ssDNA-binding protein, Replication Protein A (RPA), is a sensor of R-loops. RPA recruits and stimulates the activity of RNaseH1, an enzyme that specifically hydrolyzes the RNA moiety within RNA:DNA hybrids. How RPA-RNaseH1 interaction is regulated in cells is not known. Here, we provide evidence that phosphorylation of RNaseH1 is crucial for RPA-RNaseH1 interaction. RNaseH1 phospho-mutant at serine 76 (S76A), but not the phospho-mimetic mutant (S76E), disrupts its interaction with RPA. Importantly, expression of RNaseH1-S76A mutant, but not RNaseH1-S76E mutant, failed to suppress R-loop-associated genomic instability. Future studies will investigate how RNaseH1 phosphorylation affects its enzymatic activity and cellular functions. Altogether, these findings highlight a new phosphorylation circuitry by an unknown kinase critical for R-loop resolution through RNaseH1 function.
Keywords: RNaseH1, R-loop, Phosphorylation