Epstein-Barr nuclear antigen leader protein coactivates transcription through interaction with histone deacetylase 4

Epstein-Barr nuclear antigen (EBNA) leader protein (EBNALP) co-activates promoters with EBNA2 and is important for Epstein-Barr virus immortalization of B cells. Investigation of the role of histone cleacetylases (HDACs) in EBNALP and EBNA2 promoter regulation has now identified EBNALP and EBNA2 to be associated with HIDAC4 in a lymphoblastoid cell line. Furthermore, a transcription-deficient EBNALP point mutant did not associate with HDAC4. HIDAC4 and 5 overexpression repressed EBNA2 activation and EBNALP coactivation, whereas other HDACs had little effect. Moreover, EBNALP expression decreased nuclear HDAC4. Expression of 14-3-3 anchors HDAC4 in the cytoplasm, increased EBNALP effects, and reversed HDAC4 or 5 repression. HIDAC4 reversal depended on the HDAC4 nuclear export sequence. Consistent with EBNALP coactivation being mediated by nuclear HIDAC4 depletion, HIDAC4 overexpression increased nuclear HIDAC4 and specifically repressed EBNA2-dependent activation as well as EBNALP-dependent coactivation. Also, EBNALP, HDAC4, and 14-3-3 could be immunoprecipitated in a single complex. Thus, these data strongly support a model in which EBNALP coactivates transcription by relocalizing HIDAC4 and 5 from EBNA2 activated promoters to the cytoplasm. The observed EBNALP effects are likely also in part through HIDAC5, which is highly homologous to HIDAC4.