Amino acids of Epstein-Barr virus nuclear antigen 3A essential for repression of Jkappa-mediated transcription and their evolutionary conservation.
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.
Dalbiès-Tran
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Program in Viral Oncogenesis and Tumor Immunology, Department of Virology and Molecular Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
Stigger-Rosser
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Dotson
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Sample
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D000595:Amino Acid Sequence; D005075:Biological Evolution; D017124:Conserved Sequence; D019309:Epstein-Barr Virus Nuclear Antigens / Q000737:chemistry* / Q000502:physiology; D006801:Humans; D008969:Molecular Sequence Data; D012097:Repressor Proteins / Q000737:chemistry* / Q000502:physiology; D017385:Sequence Homology; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000502:physiology*; D014407:Tumor Cells, Cultured
D019309:Epstein-Barr Virus Nuclear Antigens; D012097:Repressor Proteins; D014157:Transcription Factors