The Herpes Simplex Virus Type 1 (HSV-1) Regulatory Protein ICP0 Interacts with and Ubiquitinates p53

Herpes simplex virus type 1 regulatory protein ICP0 contains a zinc-binding RING finger and has been shown to induce the proteasome-dependent degradation of a number of cellular proteins in a RING finger-dependent manner during infection. This domain of ICP0 is also required to induce the formation of unanchored polyubiquitin chains in vitro in the presence of ubiquitin-conjugating enzymes UbcH5a and UbcH6. These data indicate that ICP0 has the potential to act as a RING finger ubiquitin ubiquitin-protein isopeptide ligase (E3) and to induce the degradation of certain cellular proteins through ubiquitination and proteasome-mediated degradation. Here we demonstrate that ICP0 is a genuine RING finger ubiquitin E3 ligase that can interact with and mediate the ubiquitination of the major oncoprotein p53 both in vitro and in vivo. Ubiquitination of p53 requires ICP0 to have an intact RING finger domain and occurs independently of its ability to bind to the ubiquitin-specific protease USP7.