Open AccessAmino Acids of Epstein-Barr Virus Nuclear Antigen 3A Essential for Repression of Jκ-Mediated Transcription and Their Evolutionary Conservation
Author(s) -
Rozenn Dalbiès-Tran,
Evelyn Stigger-Rosser,
Travis Dotson,
Clare E. Sample
Publication year - 2001
Publication title -
journal of virology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.617
H-Index - 292
eISSN - 1070-6321
pISSN - 0022-538X
DOI - 10.1128/jvi.75.1.90-99.2001
Subject(s) - biology , amino acid , transcription (linguistics) , psychological repression , mutant , transcription factor , virus , dna binding protein , microbiology and biotechnology , gene , genetics , gene expression , philosophy , linguistics
Epstein-Barr virus (EBV) nuclear antigen 3A (EBNA-3A) is essential for virus-mediated immortalization of B lymphocytes in vitro and is believed to regulate transcription of cellular and/or viral genes. One known mechanism of regulation is through its interaction with the cellular transcription factor Jkappa. This interaction downregulates transcription mediated by EBNA-2 and Jkappa. To identify the amino acids that play a role in this interaction, we have generated mutant EBNA-3A proteins. A mutant EBNA-3A protein in which alanine residues were substituted for amino acids 199, 200, and 202 no longer downregulated transcription. Surprisingly, this mutant protein remained able to coimmunoprecipitate with Jkappa. Using a reporter gene assay based on the recruitment of Jkappa by various regions spanning EBNA-3A, we have shown that this mutation abolished binding of Jkappa to the N-proximal region (amino acids 125 to 222) and that no other region of EBNA-3A alone was sufficient to mediate an association with Jkappa. To determine the biological significance of the interaction of EBNA-3A with Jkappa, we have studied its conservation in the simian lymphocryptovirus herpesvirus papio (HVP) by cloning HVP-3A, the homolog of EBNA-3A encoded by this virus. This 903-amino-acid protein exhibited 37% identity with its EBV counterpart, mainly within the amino-terminal half. HVP-3A also interacted with Jkappa through a region located between amino acids 127 and 223 and also repressed transcription mediated through EBNA-2 and Jkappa. The evolutionary conservation of this function, in proteins that have otherwise significantly diverged, argues strongly for an important biological role in virus-mediated immortalization of B lymphocytes.