Identification of major phosphorylation sites of epstein-barr virus nuclear antigen leader protein (EBNA-LP): Ability of EBNA-LP to induce latent membrane protein 1 cooperatively with EBNA-2 is regulated by phosphorylation

Akihiko Yokoyama, Michiko Tanaka, Go Matsuda, Kentaro Kato, Mikiko Kanamori, Hiroshi Kawasaki, Hisashi Hirano, Issay Kitabayashi, Misao Ohki, Kanji Hirai, Yasushi Kawaguchi

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42 Citations (Scopus)

Abstract

Epstein-Barr virus (EBV) nuclear antigen leader protein (EBNA-LP) is a phosphoprotein suggested to play important roles in EBV-induced immortalization of B cells. One of the potential functions of EBNA-LP is a cooperative induction with EBNA-2 of viral and cellular gene expression, including that of the genes for viral latent membrane protein 1 (LMP-1) and cellular cyclin D2. We report here that the phosphorylation of EBNA-LP by cellular kinase(s) is critical to its ability to cooperate with EBNA-2 in up-regulating the expression of LMP-1 in a B-lymphoma cell line. Our conclusion is based on the following observations. (i) Mass-spectrometric analysis of purified EBNA-LP and mutational analyses of EBNA-LP revealed that the serine residue at position 35 in the W2 repeat domain is the major phosphorylation site of EBNA-LP in vivo. (ii) Substitutions of this site in each W2 repeat domain with alanine markedly reduced the ability of the protein to induce LMP-1 expression in combination with EBNA-2 in Akata cells. (iii) Replacement at the major phosphorylation sites with glutamic acids restored the wild-type phenotype. It is well established that this substitution mimics constitutive phosphorylation. These results indicated that the coactivator function of EBNA-LP is regulated by phosphorylation.

Original languageEnglish
Pages (from-to)5119-5128
Number of pages10
JournalJournal of virology
Volume75
Issue number11
DOIs
Publication statusPublished - 2001

ASJC Scopus subject areas

  • Microbiology
  • Immunology
  • Insect Science
  • Virology

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