Mitosis-specific hyperphosphorylation of Epstein-Barr virus nuclear antigen 2 suppresses its function.
The Epstein-Barr virus (EBV) nuclear antigen 2 (EBNA-2) is a key gene expressed in EBV type III latent infection that can transactivate numerous promoters, including those for all the other type III viral latency genes as well as cellular genes responsible for cell proliferation. EBNA-2 is essential for EBV-mediated immortalization of primary B lymphocytes. We now report that EBNA-2, a phosphoprotein, is hyperphosphorylated specifically in mitosis. Evidence that the cyclin-dependent kinase p34(cdc2) may be involved in this hyperphosphorylation includes (i) coimmunoprecipitation of EBNA-2 and p34(cdc2), suggesting physical association; (ii) temporal correlation between hyperphosphorylation of EBNA-2 and an increase in p34(cdc2) kinase activity; and (iii) ability of purified p34(cdc2)/cyclin B1 kinase to phosphorylate EBNA-2 in vitro. Hyperphosphorylation of EBNA-2 appears to suppress its ability to transactivate the latent membrane protein 1 (LMP-1) promoter by about 50%. The association between EBNA-2 and PU.1 is also decreased by about 50% in M-phase-arrested cells, as shown by coimmunoprecipitation from cell lysates, suggesting that hyperphosphorylation of EBNA-2 impairs its affinity for PU.1. Finally, endogenous LMP-1 mRNA levels in M phase are around 55% of those in asynchronously growing cells. These results suggest that regulation of gene expression during type III latency may be regulated in a cell-cycle-related manner.
Yue
Wei
W
Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Davenport
Matthew G
MG
Shackelford
Julia
J
Pagano
Joseph S
JS
D016203:CDC2 Protein Kinase / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D019309:Epstein-Barr Virus Nuclear Antigens / Q000737:chemistry / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral; D006367:HeLa Cells; D006801:Humans; D008938:Mitosis; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism; D014763:Viral Matrix Proteins / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins; D000099232:Proto-Oncogene Protein Spi-1
D016203:CDC2 Protein Kinase; D019926:Cyclin B; D056744:Cyclin B1; D019309:Epstein-Barr Virus Nuclear Antigens; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D015534:Trans-Activators; D014763:Viral Matrix Proteins; D014764:Viral Proteins; D000099232:Proto-Oncogene Protein Spi-1; C534699:CCNB1 protein, human; C402641:EBNA-2 protein, Human herpesvirus 4; C037662:EBV-associated membrane antigen, Epstein-Barr virus