Epstein-Barr Virus Nuclear Antigen 3A Promotes Cellular Proliferation by Repression of the Cyclin-Dependent Kinase Inhibitor p21WAF1/CIP1

PLoS Pathogens

Keith C. Wanzeck¹  Robert E. Throm¹  Melissa L. Tursiella²  Emily R. Bowman²  Clare E. Sample²  Junjia Zhu³  Jason Liao³ 

[1] Department of Biochemistry, St. Jude Children's Research Hospital, Memphis, Tennessee, United States of America;Department of Microbiology and Immunology, Pennsylvania State University College of Medicine, and the Penn State Hershey Cancer Institute, Hershey, Pennsylvania, United States of America;Department of Public Health Sciences, Pennsylvania State University College of Medicine, and the Penn State Hershey Cancer Institute, Hershey, Pennsylvania, United States of America

关键词: Apoptosis;    Cyclins;    Immunoblotting;    Transfection;    Cell cycle;    cell division;    Lamins;    Viral persistence;    latency;    Epstein-Barr virus;   

DOI  :  10.1371/journal.ppat.1004415

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Latent infection by Epstein-Barr virus (EBV) is highly associated with the endemic form of Burkitt lymphoma (eBL), which typically limits expression of EBV proteins to EBNA-1 (Latency I). Interestingly, a subset of eBLs maintain a variant program of EBV latency - Wp-restricted latency (Wp-R) - that includes expression of the EBNA-3 proteins (3A, 3B and 3C), in addition to EBNA-1. In xenograft assays, Wp-R BL cell lines were notably more tumorigenic than their counterparts that maintain Latency I, suggesting that the additional latency-associated proteins expressed in Wp-R influence cell proliferation and/or survival. Here, we evaluated the contribution of EBNA-3A. Consistent with the enhanced tumorigenic potential of Wp-R BLs, knockdown of EBNA-3A expression resulted in abrupt cell-cycle arrest in G0/G1 that was concomitant with conversion of retinoblastoma protein (Rb) to its hypophosphorylated state, followed by a loss of Rb protein. Comparable results were seen in EBV-immortalized B lymphoblastoid cell lines (LCLs), consistent with the previous observation that EBNA-3A is essential for sustained growth of these cells. In agreement with the known ability of EBNA-3A and EBNA-3C to cooperatively repress p14ARF and p16INK4a expression, knockdown of EBNA-3A in LCLs resulted in rapid elevation of p14ARF and p16INK4a. By contrast, p16INK4a was not detectably expressed in Wp-R BL and the low-level expression of p14ARF was unchanged by EBNA-3A knockdown. Amongst other G1/S regulatory proteins, only p21WAF1/CIP1, a potent inducer of G1 arrest, was upregulated following knockdown of EBNA-3A in Wp-R BL Sal cells and LCLs, coincident with hypophosphorylation and destabilization of Rb and growth arrest. Furthermore, knockdown of p21WAF1/CIP1 expression in Wp-R BL correlated with an increase in cellular proliferation. This novel function of EBNA-3A is distinct from the functions previously described that are shared with EBNA-3C, and likely contributes to the proliferation of Wp-R BL cells and LCLs.

【 授权许可】

CC BY