Lysine acetylation plays a role in RNA binding protein-regulated alternative pre-mRNA splicing

Alternative pre-mRNA splicing allows one gene to encode multiple spliced messenger RNAs and, in turn, multiple proteins from a single gene transcript. This process is tightly regulated by cis elements within the pre-mRNA and trans-acting RNA binding proteins that recognize and bind to these elements, thus influencing the spliceosome assembly at adjacent splice sites. Thus, chemical modifications in either the cis-elements or trans factors or both can significantly alter splicing patterns and, thereby, the cellular proteome. Recent studies highlight that many RNA binding proteins (RBPs) are modified at multiple lysine side chains via acetylation, which neutralizes the formal positive charge and disrupts RPBs' ability to participate in RNA recognition, binding and protein-protein interactions. This suggests that lysine acetylation of RPBs may be a novel mode of eukaryotic gene regulation during pre-mRNA processing. To test this, we used the well-characterized polypyrimidine tract binding protein (which is acetylated at several lysine side chains) as a model system to investigate the role of reversible RBP acetylation in regulating alternative-pre mRNA splicing. Using multiple sequence analysis, structure-based electrostatic modeling of RNA-protein interactions, and multi-site glutamine (acetyllysine mimic) and arginine (deacetyllysine mimic) mutants, we show for the first time that for a subset of PTBP1-regulated exons, acetylation at RNA-interacting lysine side chains significantly alters PTBP1 splicing activity.