Hepatitis C Virus Core Induces p53 Ser-15 Phosphorylation to Facilitate E6-Associated Protein-Mediated Proteasomal Degradation of p53

The hepatitis C virus (HCV) Core activates the ATM-Chk2 pathway, leading to phosphorylation of p53 at Ser-15, which inhibits mouse double minute 2 (MDM2)-mediated proteasomal degradation. This study reveals that HCV Core also promotes E6-associated protein (E6AP)-mediated degradation of p53 during HCV replication. In the presence of HCV Core, E6AP expression induced p53 ubiquitination, reduced its stability, and decreased p53 levels, whereas E6AP knockdown increased p53 levels. The E3 ubiquitin ligase activity of E6AP was critical for this process, as demonstrated using the E6AP C833A mutant and the E3 ligase inhibitor Heclin. Proteasomal inhibition with MG132 confirmed that HCV Core and E6AP act together to regulate p53 levels via the proteasome. Importantly, HCV Core-induced p53 phosphorylation was essential for E6AP-mediated degradation, as shown by the impairment of degradation in the presence of the ATM inhibitor KU-55933. E6AP also targeted p53 phosphorylated at Ser-15 by etoposide, as well as phosphomimetic mutants such as p53 S15D, but not non-phosphorylatable mutants such as p53 S15A. These findings suggest that HCV Core-induced p53 phosphorylation enhances E6AP-mediated degradation while preventing MDM2 from targeting p53, thereby maintaining p53 levels that support cell survival, viral replication, and potentially oncogenesis in human hepatocytes.