Ubiquitin-specific-processing protease 7 (USP7), also known as ubiquitin carboxyl-terminal hydrolase 7 or herpesvirus-associated ubiquitin-specific protease (HAUSP), is an enzyme that in humans is encoded by the USP7 gene. USP7 or HAUSP is a ubiquitin specific protease or a deubiquitylating enzyme that cleaves ubiquitin from its substrates.[9] Since ubiquitylation (polyubiquitination) is most commonly associated with the stability and degradation of cellular proteins, HAUSP activity generally stabilizes its substrate proteins. Another important role of HAUSP function involves the oncogenic stabilization of p53. Oncogenes such as Myc and E1A are thought to activate p53 through a p19 alternative reading frame (p19ARF, also called ARF)-dependent pathway, although some evidence suggests ARF is not essential in this process. A possibility is that HAUSP provides an alternative pathway for safeguarding the cell against oncogenic insults. USP7 can deubiquitinate histone H2B and this activity is associated with gene silencing in Drosophila. USP7 associates with a metabolic enzyme, GMP synthetase (GMPS) and this association stimulates USP7 deubiquitinase activity towards H2B. The USP7-GMPS complex is recruited to the polycomb (Pc) region in Drosophila and contributes to epigenetic silencing of homeotic genes.