Abstract
In B lymphocytes induced to proliferate in vitro by the Epstein-Barr virus (EBV), extra-chromosomal viral episomes packaged in chromatin persist in the nucleus, and there is no productive cycle. A switch from this latency to the productive cycle is observed after induced expression of the EBV BZLF1 gene product, the transcription factor EB1. We present evidence that, during latency, proteins of the myocyte enhancer binding factor 2 (MEF2) family are bound to the BZLF1 promoter and recruit class II histone deacetylases. Furthermore, we propose that latency is determined primarily by a specific and local recruitment of class II histone deacetylase (HDAC) by MEF2D to the BZLF1 gene promoter. The switch from latency to the productive cycle could be due in part to post-translational modification of MEF2 proteins and changes in the local acetylation state of the chromatin.