Epstein-Barr virus polymerase processivity factor enhances BALF2 promoter transcription as a coactivator for the BZLF1immediate-early protein

Sanae Nakayama, Takayuki Murata, Kazutaka Murayama, Yoshihiro Yasui, Yoshitaka Sato, Ayumi Kudoh, Satoko Iwahori, Hiroki Isomura, Teru Kanda, Tatsuya Tsurumi

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

The Epstein-Barr virus (EBV) BMRF1 protein is an essential replication protein acting at viral replication forks as a viral DNA polymerase processivity factor, whereas the BALF2 protein is a singles-tranded DNA-binding protein that also acts at replication forks and is most abundantly expressed during viral productive replication. Here we document that the BMRF1 protein evidently enhances viral BZLF1 transcription factor-mediated transactivation of the BALF2 gene promoter. Mutagenesis and electrophoretic mobility shift assays demonstrated the BALF2 promoter to harbor two BZLF1 protein-binding sites (BZLF1-responsive elements). Direct binding of the BZLF1 protein to BZLF1-responsive elements and physical interaction between BZLF1 and BMRF1 proteins are prerequisite for the BMRF1 protein up-regulation of the BALF2 gene promoter. A monomeric mutant, C95E, which is defective in homodimerization, could still interact and enhance BZLF1-mediated transactivation. Furthermore although EBV protein kinase phosphorylates BMRF1 protein extensively, it turned out that phosphorylation of the protein by the kinase is inhibitory to the enhancement of the BZLF1-mediated transactivation of BALF2 promoter. Exogenous expression of BMRF1 protein augmented BALF2 expression in HEK293 cells harboring the EBV genome but lacking BMRF1 and BALF5 genes, demonstrating functions as a transcriptional regulator in the context of viral infection. Overall the BMRF1 protein is a multifunctional protein that cannot only act as a DNA polymerase processivity factor but also enhances BALF2 promoter transcription as a coactivator for the BZLF1 protein, regulating the expression level of viral single-stranded DNA-binding protein.

Original languageEnglish
Pages (from-to)21557-21568
Number of pages12
JournalJournal of Biological Chemistry
Volume284
Issue number32
DOIs
Publication statusPublished - 07-08-2009
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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