Cell cycle stage-specific phosphorylation of the Epstein-Barr virus immortalization protein EBNA-LP

Kitay, Mary Kate; Rowe, David

doi:10.1128/jvi.70.11.7885-7893.1996

Cited by 46 publications

(21 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1B) completely matches the consensus phosphorylation site for cdc2 [(S/T)PX(KR); Marin et al, 1992]. (ii) EBNA-LP can be phosphorylated by cdc2 in vitro (Kitay & Rowe, 1996a). (iii) In EBV-infected cells, EBNA-LP is highly phosphorylated in the G 2 /M phase, when the activity of cdc2 is specifically upregulated (Kitay & Rowe, 1996a;Smits & Medema, 2001).…”

Section: Cellular Protein Kinase Cdc2 Targets the Functional Phosphormentioning

confidence: 61%

Identification of protein kinases responsible for phosphorylation of Epstein–Barr virus nuclear antigen leader protein at serine-35, which regulates its coactivator function

Kato

Yokoyama

Tohya

et al. 2003

Journal of General Virology

View full text Add to dashboard Cite

Epstein-Barr virus (EBV) nuclear antigen leader protein (EBNA-LP) is a phosphoprotein suggested to play important roles in EBV-induced immortalization. Earlier studies have shown that the major site of phosphorylation of EBNA-LP by cellular kinase(s) is a serine residue at position 35 and that the phosphorylation of Ser-35 is critical for regulation of the coactivator function of EBNA-LP (Yokoyama et al., J Virol 75, 5119-5128, 2001). In the present study, we have attempted to identify protein kinase(s) responsible for the phosphorylation of EBNA-LP at Ser-35. A purified chimeric protein consisting of glutathione S-transferase (GST) fused to a domain of EBNA-LP containing Ser-35 was found to be specifically phosphorylated by purified cdc2 in vitro, while GST fused to a mutated domain of EBNA-LP in which Ser-35 was replaced with alanine was not. In addition, overexpression of cdc2 in mammalian cells caused a significant increase in the phosphorylation of EBNA-LP, while this increased phosphorylation was eliminated if Ser-35 of EBNA-LP was replaced with alanine. These results indicate that the cellular protein kinase cdc2 mediates the phosphorylation of EBNA-LP at Ser-35. Recently, we reported that cdc2 and conserved protein kinases encoded by herpesviruses phosphorylate the same amino acid residue of target proteins (Kawaguchi et al., J Virol 77, 2359-2368, 2003. Consistent with this, the EBV-encoded conserved protein kinase BGLF4 specifically mediated the phosphorylation of EBNA-LP at Ser-35. These results indicate that the coactivator function of EBNA-LP can be regulated by the activity of these cellular and viral protein kinases. INTRODUCTIONEpstein-Barr virus (EBV) is a ubiquitous human herpesvirus that is frequently associated with infectious mononucleosis and a variety of human malignancies including Burkitt's lymphoma, nasopharyngeal carcinoma, Hodgkin's disease, gastric carcinoma and various lymphomas . In vitro, EBV can readily infect and immortalize human B cells . The resultant lymphoblastoid cell lines (LCLs) carry the entire 180 kbp EBV genome encoding more than 80 viral proteins in an episomal and latent state, express only a limited number of viral proteins, including EBNA-1, EBNA-2, EBNA-3A, EBNA-3B, EBNA-3C, EBNA-LP, LMP-1, LMP-2A and LMP-2B, and produce no viral progeny ). Among these latencyassociated EBV proteins, EBNA-1, EBNA-2, EBNA-3A, EBNA-3C, EBNA-LP and LMP-1 are critical for EBVinduced B-cell immortalization, whereas EBNA-3B, LMP-2A and LMP-2B are not (Cohen et al., 1989;Hammerschmidt & Sugden, 1989;Kaye et al., 1993;Mannick et al., 1991;Marchini et al., 1992; Tomkinson et al., 1993). Lytic (or productive) infection can be induced experimentally by the treatment of latently infected cells with chemical reagents such as phorbol ester and sodium butyrate Luka et al., 1979; zur Hausen et al., 1978), and following induction of virus replication, abundant transcription of a large portion of the genome, the synthesis of many new viral polypeptides, amplification of viral DNA and release o...

show abstract

Section: Cellular Protein Kinase Cdc2 Targets the Functional Phosphormentioning

confidence: 61%

Identification of protein kinases responsible for phosphorylation of Epstein–Barr virus nuclear antigen leader protein at serine-35, which regulates its coactivator function

Kato

Yokoyama

Tohya

et al. 2003

Journal of General Virology

View full text Add to dashboard Cite

show abstract

“…The EBV latent immortalizing genes EBNA-LP and EBNA-2, for example, induce cyclin D2 expression (17,21,41). Although EBNA-LP protein levels are stable throughout the cell cycle, this protein is phosphorylated in a cell cycle stage-specific manner, suggesting possible functional regulation (22). KSHV also indirectly inactivates pRB through pRB phosphorylation in conjunction with cyclin-dependent kinase 6 (CDK 6).…”

Section: Discussionmentioning

confidence: 99%

Characterization and Cell Cycle Regulation of the Major Kaposi’s Sarcoma-Associated Herpesvirus (Human Herpesvirus 8) Latent Genes and Their Promoter

Sarid

Wiezorek

Moore

et al. 1999

J Virol

163

View full text Add to dashboard Cite

Retinoblastoma tumor suppressor protein (pRB) inhibition by tumor virus oncoproteins has been attributed to the need for these viruses to promote lytic viral nucleic acid synthesis by unscheduled entry into the S phase of the cell cycle. Kaposi’s sarcoma-associated herpesvirus (KSHV or HHV8) encodes a functional cyclin (vCYC) which is expressed during latency and can direct phosphorylation of pRB. We mapped the two major latent transcripts encoding vCYC, latent transcript 1 (LT1) and LT2, by cDNA sequencing, 5′ rapid amplification of cDNA ends, and primer extension analyses. Both LT1 and LT2 transcripts are spliced, originate from the same start site, and encode ORF K13 (vFLIP) as well as ORF72 (vCYC). The latency-associated nuclear antigen (LANA, ORF73) is encoded by LT1 but spliced from LT2. While differential expression of the two transcripts was not found, the promoter controlling LT1/LT2 transcription is regulated in a cell cycle-dependent manner. Activities of both KSHV LT1/LT2 and huCYC D1 luciferase promoter reporters transfected into NIH 3T3 cells increase 11- and 4-fold, respectively, after release from cell cycle arrest by serum starvation. Further, vCYC and huCYC D2 mRNA levels are low in naturally infected BCBL-1 cells arrested in late G1 with l-mimosine but increase in parallel during a 24-h period after release from cell cycle arrest. Cell cycle regulation of KSHV vCYC expression mimics cellular D cyclin regulation and may maintain infected cell cycling. This is consistent with an alternative hypothesis that tumor viruses have developed specific responses to innate cellular defenses against latent virus infection that include pRB-induced cell cycle arrest.

show abstract

“…Specific inhibitors that block cdc2 activity reduce HSV-1 viral [75]. Several herpesvirus proteins are phosphorylated by cdc2; more than one-third of HSV-1 proteins possess consensus target sites for cdc2 phosphorylation [74,[76][77][78]. Therefore, CHPKs may be involved in the various cellular events which are normally regulated by cdc2 activity.…”

Section: Functional Cdc2-mimicry By Chpks and Its Significance: A Hypmentioning

confidence: 99%

Protein kinases conserved in herpesviruses potentially share a function mimicking the cellular protein kinase cdc2

Kawaguchi

Kato

2003

Reviews in Medical Virology

View full text Add to dashboard Cite

Herpesviruses encode protein kinases. A subset of these proteins, represented by HSV-1 UL13, are conserved throughout all members of the Herpesviridae, and here, are designated CHPKs (conserved herpesvirus protein kinases). In addition to conserved gene products like CHPKs, herpesviruses encode genes specific to respective herpesviruses. When acting upon conserved viral gene products or cellular factors, CHPKs may play conserved roles in the life cycles of herpesviruses. CHPKs may also express unique functions within the infectious process of individual herpesviruses when specific viral gene products are targeted. CHPKs demonstrate specific activity in multiple herpesvirus infections, functioning in the regulation of viral gene expression in HSV-1, tissue tropism in VZV, and viral DNA synthesis, encapsidation and egress from the nucleus in HCMV. The HCMV CHPK, however, can partially substitute for the HSV-1 CHPK. Representative CHPKs from all Herpesviridae subfamilies can also facilitate the hyperphosphorylation of the cellular translation factor, EF-1delta. This indicates that CHPKs have conserved functions. Recent data have shown that both CHPKs and a cellular protein kinase, cdc2, phosphorylate the same amino acid residues of target proteins. Thus, CHPKs may mimic cdc2 function in infected cells.

show abstract

Cell cycle stage-specific phosphorylation of the Epstein-Barr virus immortalization protein EBNA-LP

Cited by 46 publications

References 45 publications

Identification of protein kinases responsible for phosphorylation of Epstein–Barr virus nuclear antigen leader protein at serine-35, which regulates its coactivator function

Identification of protein kinases responsible for phosphorylation of Epstein–Barr virus nuclear antigen leader protein at serine-35, which regulates its coactivator function

Characterization and Cell Cycle Regulation of the Major Kaposi’s Sarcoma-Associated Herpesvirus (Human Herpesvirus 8) Latent Genes and Their Promoter

Protein kinases conserved in herpesviruses potentially share a function mimicking the cellular protein kinase cdc2

Contact Info

Product

Resources

About