MOLECULAR MECHANISM OF CO-ACTIVATION ACTIVITIES OF EPSTEIN-BARR VIRUS NUCLEARPROTEIN EBNA-LP

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Epstein-Barr virus (EBV) infection causes cell growth transformation of primary human B lymphocyte. EBV nuclear proteins EBNA-2 and EBNA-LP play critical roles on the transformation. Those proteins are expressed simultaneously in early stage of EBV infection. EBNA-2 is a transactivator that up-regulates transcriptional activities of both viral and cellular promoters. EBNA-LP stimulates the EBNA-2 mediated transactivation as a cofactor (Harada a ＆ Kieff, J.Virol., 1997). To address the molecular mechanism of transcriptional activation which EBNA-2 and EBNA-LP cooperatively regulate to establish the EBV latent infection, we investigate direct and indirect interaction of those EBNAs, and the association of EBNA-LP with cellular proteins.(1) EBNA-LP-associated proteins were identified by sequencing proteins that immunoprecipitated with flag-tagged EBNA-LP from B lymphoblast cells in which flag-LP was stably expressed. The association of EBNA-LP with Hsp70 (72/73) was confirmed, and sequences of DNA-PK catalytic subunit, HA95, Hsp27, prolyl 4-hydroxylase α-1 subunit, α-tublin, β-tublin, were identified (J.Virol., 2001b).(2) EBNA-2 has at least two domains, amino acids 1 to 60 and 96 to 210, which independently mediate homotypic association. EBNA-2 self-association is likely to be critical to the ability of EBNA-2 to interact simultaneously with multiple cellular transcription factors and coactivators through its interaction domain to cellular DNA binding proteins and its acidic activation domain (J.Virol., 2001a).(3) We identified HAX-1 protein that associates with EBNA-LP in both yeast and human lymphocytes using the yeast two-hybrid screening. HAX-1 is reported to be a cytoplasmic protein that locates in mitochondria and associates with HS1 that is a substrate of B cell receptor associated kinase.