the herpesvirus associated ubiquitin specific protease, usp7, is a negative regulator of pml proteins and pml nuclear bodies泛素相关的疱疹病毒特定的蛋白酶,usp7,pml蛋白和pml核体的负面调节器.pdf

The Herpesvirus Associated Ubiquitin Specific Protease, USP7, Is a Negative Regulator of PML Proteins and PML Nuclear Bodies Feroz Sarkari, Xueqi Wang, Tin Nguyen, Lori Frappier* Department of Molecular Genetics, University of Toronto, Toronto, Canada Abstract The PML tumor suppressor is the founding component of the multiprotein nuclear structures known as PML nuclear bodies (PML-NBs), which control several cellular functions including apoptosis and antiviral effects. The ubiquitin specific protease USP7 (also called HAUSP) is known to associate with PML-NBs and to be a tight binding partner of two herpesvirus proteins that disrupt PML NBs. Here we investigated whether USP7 itself regulates PML-NBs. Silencing of USP7 was found to increase the number of PML-NBs, to increase the levels of PML protein and to inhibit PML polyubiquitylation in nasopharyngeal carcinoma cells. This effect of USP7 was independent of p53 as PML loss was observed in p53-null cells. PML-NBs disruption was induced by USP7 overexpression independently of its catalytic activity and was induced by either of the protein interaction domains of USP7, each of which localized to PML-NBs. USP7 also disrupted NBs formed from some single PML isoforms, most notably isoforms I and IV. CK2a and RNF4, which are known regulators of PML, were dispensable for USP7- associated PML-NB disruption. The results are consistent with a novel model of PML regulation where a deubiquitylase disrupts PML-NBs through recruitment of another cellular protein(s) to PML NBs, independently of its catalytic activity. Citation: Sarkari F, Wang X, Nguyen T, Frappier L (2011) The Herpesvirus Associated Ubiquitin Specific Protease, USP7, Is a Negative Regulator of PML Proteins and PML Nuclear Bodies. PLoS ONE 6(1): e16598. doi:10.1371/journal.pone.0016598 Editor: David Harrich, Queensland Institut