USP7

Ubiquitin specific peptidase 7 (herpes virus-associated)

PDB rendering based on 1nb8.
Identifiers
Symbols USP7; HAUSP; TEF1
External IDs OMIM: 602519 MGI: 2182061 HomoloGene: 2592 GeneCards: USP7 Gene
EC number 3.4.19.12
RNA expression pattern
More reference expression data
Orthologs
Species Human Mouse
Entrez 7874 252870
Ensembl ENSG00000187555 ENSMUSG00000022710
UniProt Q93009 Q6A4J8
RefSeq (mRNA) NM_003470 NM_001003918.2
RefSeq (protein) NP_003461 NP_001003918.2
Location (UCSC) Chr 16:
8.99 – 9.06 Mb		 Chr 16:
8.69 – 8.79 Mb
PubMed search [1] [2]

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.[1][2][3][4]

Contents

Function

Regulation of the p53 tumor suppressor

USP7 or HAUSP is a ubiquitin specific protease or a deubiquitylating enzyme that cleaves ubiquitin from its substrates.[5] Since ubiquitylation (polyubiquitination) is most commonly associated with the stability and degradation of cellular proteins, HAUSP acitivity generally stabilizes its substrate proteins. HAUSP is most popularly known as a direct antagonist of Mdm2, the E3 ubiquitin ligase for the tumor suppressor protein, p53.[6] Normally, p53 levels are kept low in part due to Mdm2-mediated ubiquitylation and degradation of p53. Interestingly, in response to oncogenic insults, HAUSP can deubiquitinate p53 and protect p53 from Mdm2-mediated degradation, indicating that it may possess a tumor suppressor function for the immediate stabilization of p53 in response to stress. 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. An intriguing possibility is that HAUSP provides an alternative pathway for safeguarding the cell against oncogenic insults.

Role in transcriptional regulation

USP7 can deubiquitinate histone H2B and this activity is associated with gene silencing in Drosophila.[7] USP7 associates with a metabolic enzyme, GMP synthetase (GMPS) and this association stimulates USP7 deubiquitinase activity towards H2B.[7] The USP7-GMPS complex is recruited to the polycomb (Pc) region in Drosophila and contributes to epigenetic silecing of homeotic genes.[8]

Association with herpesviruses

USP7 was originally identified as a protein associated with the ICP0 protein of herpes simplex virus (HSV), hence the name Herpesvirus Associated USP (HAUSP). ICP0 is an E3-ubiquitin ligase that is involved in ubiquitination and subsequent degradation of itself and certain cellular proteins. USP7 has been shown to regulate the auto-ubiquitination and degradation of ICP0.

More recently, an interaction between USP7 and the EBNA1 protein of Epstein-Barr virus (EBV) (another herpesvirus) was also discovered.[9] This interaction is particularly interesting given the oncogenic potential (potential to cause cancer) of EBV, which is associated with several human cancers. EBNA1 can compete with p53 for binding USP7. Stabilization by USP7 is important for the tumor suppressor function of p53. In cells, EBNA1 can sequester USP7 from p53 and thus attenuate stabilization of p53, rendering the cells predisposed to turning cancerous. Compromising the function of p53 by sequestering USP7 is one way EBNA1 can contribute to the oncogenic potential of EBV. Additionally, human USP7 was also shown to form a complex with GMPS and this complex is recruited to EBV genome sequences.[10] USP7 was shown to be important for histone H2B deubiquitination in human cells and for deubiquitination of histone H2B incorporated in the EBV genome. Thus USP7 may also be important for regulation of viral gene expression.

The fact that viral proteins have evolved so as to target USP7, underscores the significance of USP7 in tumor suppression and other cellular processes.

Binding partners

The following is a list of some of the known cellular binding partners of USP7/HAUSP:

Interactions

USP7 has been shown to interact with Ataxin 1,[11] CLSPN[12] and P53.[6] A proteomic screen conducted to identify interacting partners of 75 human deubiquitinating enzymes (DUBs) has revealed several novel binding partners of USP7.[13]

References

  1. ^ Puente XS, Sanchez LM, Overall CM, Lopez-Otin C (Jul 2003). "Human and mouse proteases: a comparative genomic approach". Nat Rev Genet 4 (7): 544–58. doi:10.1038/nrg1111. PMID 12838346. 
  2. ^ Robinson PA, Lomonte P, Leek, Markham AF, Everett RD (Mar 1999). "Assignment1 of herpesvirus-associated ubiquitin-specific protease gene HAUSP to human chromosome band 16p13.3 by in situ hybridization". Cytogenet Cell Genet 83 (1–2): 100. doi:10.1159/000015142. PMID 9925944. 
  3. ^ "Entrez Gene: USP7 ubiquitin specific peptidase 7 (herpes virus-associated)". http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=7874. 
  4. ^ Everett RD, Meredith M, Orr A, Cross A, Kathoria M, Parkinson J (April 1997). "A novel ubiquitin-specific protease is dynamically associated with the PML nuclear domain and binds to a herpesvirus regulatory protein". EMBO J. 16 (7): 1519–30. doi:10.1093/emboj/16.7.1519. PMC 1169756. PMID 9130697. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1169756. 
  5. ^ Holowaty MN, Sheng Y, Nguyen T, Arrowsmith C, Frappier L (November 2003). "Protein interaction domains of the ubiquitin-specific protease, USP7/HAUSP". J. Biol. Chem. 278 (48): 47753–61. doi:10.1074/jbc.M307200200. PMID 14506283. 
  6. ^ a b Li M, Chen D, Shiloh A, Luo J, Nikolaev AY, Qin J, Gu W (April 2002). "Deubiquitination of p53 by HAUSP is an important pathway for p53 stabilization". Nature 416 (6881): 648–53. doi:10.1038/nature737. PMID 11923872. 
  7. ^ a b van der Knaap JA, Kumar BR, Moshkin YM, Langenberg K, Krijgsveld J, Heck AJ, Karch F, Verrijzer CP (March 2005). "GMP synthetase stimulates histone H2B deubiquitylation by the epigenetic silencer USP7". Mol. Cell 17 (5): 695–707. doi:10.1016/j.molcel.2005.02.013. PMID 15749019. 
  8. ^ van der Knaap JA, Kozhevnikova E, Langenberg K, Moshkin YM, Verrijzer CP (February 2010). "Biosynthetic enzyme GMP synthetase cooperates with ubiquitin-specific protease 7 in transcriptional regulation of ecdysteroid target genes". Mol. Cell. Biol. 30 (3): 736–44. doi:10.1128/MCB.01121-09. PMC 2812229. PMID 19995917. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2812229. 
  9. ^ Holowaty MN, Frappier L (November 2004). "HAUSP/USP7 as an Epstein-Barr virus target". Biochem. Soc. Trans. 32 (Pt 5): 731–2. doi:10.1042/BST0320731. PMID 15494000. 
  10. ^ Sarkari F, Sanchez-Alcaraz T, Wang S, Holowaty MN, Sheng Y, Frappier L (October 2009). Speck, Samuel H.. ed. "EBNA1-mediated recruitment of a histone H2B deubiquitylating complex to the Epstein-Barr virus latent origin of DNA replication". PLoS Pathog. 5 (10): e1000624. doi:10.1371/journal.ppat.1000624. PMC 2757719. PMID 19834552. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2757719. 
  11. ^ Hong S, Kim SJ, Ka S, Choi I, Kang S (June 2002). "USP7, a ubiquitin-specific protease, interacts with ataxin-1, the SCA1 gene product". Mol. Cell. Neurosci. 20 (2): 298–306. doi:10.1006/mcne.2002.1103. PMID 12093161. 
  12. ^ Faustrup H, Bekker-Jensen S, Bartek J, Lukas J, Mailand N (January 2009). "USP7 counteracts SCFbetaTrCP- but not APCCdh1-mediated proteolysis of Claspin". J. Cell Biol. 184 (1): 13–9. doi:10.1083/jcb.200807137. PMC 2615094. PMID 19124652. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2615094. 
  13. ^ . doi:10.1016/j.cell.2009.04.042. PMC 2716422. PMID 19615732. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2716422. 

Further reading