Epstein-Barr virus nuclear antigen 3C augments Mdm2-mediated p53 ubiquitination and degradation by deubiquitinating Mdm2
Authors: Abhik Saha
Pankaj Kumar
Bharat Bajaj
Karen Sims
Erle S Robertson
Masanao Murakami
Journal: Journal of virology (2009)
Discipline: MICROBIOLOGY
Keywords: Epstein-Barr virus; EBNA3C; deubiquitination; Mdm2; p53
Affiliations: Department of Microbiology and Tumor Virology Program of the Abramson Comprehensive Cancer Center, University of Pennsylvania Medical School, Philadelphia, PA 19104, USA., Department of Microbiology and Tumor Virology Program of the Abramson Comprehensive Cancer Center, University of Pennsylvania Medical School, 201E Johnson Pavilion, 3610 Hamilton Walk, Philadelphia, Pennsylvania 19104

Abstract:  Epstein-Barr virus (EBV) nuclear antigen 3C (EBNA3C) is one of the essential latent antigens for primary B-cell transformation. Previous studies established that EBNA3C facilitates degradation of several vital cell cycle regulators, including the retinoblastoma (pRb) and p27(KIP) proteins, by recruitment of the SCF(Skp2) E3 ubiquitin ligase complex. EBNA3C was also shown to be ubiquitinated at its N-terminal residues. Furthermore, EBNA3C can bind to and be degraded in vitro by purified 20S proteasomes. Surprisingly, in lymphoblastoid cell lines, EBNA3C is extremely stable, and the mechanism for this stability is unknown. In this report we show that EBNA3C can function as a deubiquitination enzyme capable of deubiquitinating itself in vitro as well as in vivo. Functional mapping using deletion and point mutational analysis showed that both the N- and C-terminal domains of EBNA3C contribute to the deubiquitination activity. We also show that EBNA3C efficiently deubiquitinates Mdm2, an important cellular proto-oncogene, which is known to be overexpressed in several human cancers. The data presented here further demonstrate that the N-terminal domain of EBNA3C can bind to the acidic domain of Mdm2. Additionally, the N-terminal domain of EBNA3C strongly stabilizes Mdm2. Importantly, EBNA3C simultaneously binds to both Mdm2 and p53 and can form a stable ternary complex; however, in the presence of p53 the binding affinity of Mdm2 toward EBNA3C was significantly reduced, suggesting that p53 and Mdm2 might share a common overlapping domain of EBNA3C. We also showed that EBNA3C enhances the intrinsic ubiquitin ligase activity of Mdm2 toward p53, which in turn facilitated p53 ubiquitination and degradation. Thus, manipulation of the oncoprotein Mdm2 by EBNA3C potentially provides a favorable environment for transformation and proliferation of EBV-infected cells. 

Retracted: No

PubPeer comments:
 Figure 6C. Much more similar than you would expect. https: imgur.com b7iHiHi , 
 Last author appears to be on this journalu2019s editorial board: https: jvi.asm.org content board-editors , 
 Figure 9A. * Red box: The right aMyc panel appears to only show five lanes, while six were expected. Could the authors please check?  , 
 2021 correction. https: journals.asm.org doi 10.1128 JVI.00758-21 AUTHOR CORRECTION Volume 83, no. 9, p. 4652u20134669, 2009, https: doi:10.1128 JVI.02408-08. Page 4661, Fig. 6C, part V: Due to an error that occurred during copying and pasting to generate the Fig. 6C panels, the middle (Mdm2) panel is an inadvertent duplicate of the middle (Mdm2) panel in Fig. 6C, part I. The Mdm2 panel of Fig. 6C, part V, should appear as shown below. Page 4664, Fig. 9A: The bottom right (WB: u03b1Myc Lysate) panel was inadvertently cropped, with one lane less to the left. The bottom right (WB: u03b1Myc Lysate) panel of Fig. 9A should appear as shown below. Correction of these figures does not change the conclusions of this paper. ,