Identifying Substrates, Interacting Partners and Cofactors of Pirh2: Characterizing the Pirh2-PKCdelta Interaction

p53 is a central player in the cellular response to stress, allowing cells to cope in the presence of diverse stress signals including DNA damage and oncogene activation. In response to stress, p53 acts as a transcription factor to regulate the expression of protein-coding and non-coding RNA genes that collectively result in cell cycle arrest, senescence or apoptosis. One such p53-regulated gene encodes the Pirh2 protein, an E3 ubiquitin ligase known to ubiquitinate many substrates including p53, p27/Kip1 cell cycle inhibitor and DNA polymerase η. The objective of this project was to validate a putative interaction between Pirh2 and Protein Kinase Cδ and determine if the latter was a substrate for Pirh2-mediated ubiquitination. While data suggest that Pirh2 protein expression negatively correlates with PKCδ protein levels, it could not be confirmed that Pirh2 mediates ubiquitin-dependent degradation of PKCδ protein.