
<ArticleTitle>The bovine <prot>herpesvirus 1 immediate-early protein</prot> (<prot>bICP0</prot>) associates with <prot>histone deacetylase 1</prot> to activate transcription.</ArticleTitle>
<AbstractText><prot>Infected-cell protein 0 encoded by bovine herpesvirus 1 (BHV-1)</prot> (<prot>bICP0</prot>) is necessary for efficient productive infection, in large part, because it activates all 3 classes of BHV-1 genes (U. V. Wirth, C. Fraefel, B. Vogt, C. Vlcek, V. Paces, and M. Schwyzer, J. Virol. 66:2763-2772, 1992). Although <prot>bICP0</prot> is believed to be a functional homologue of <prot>herpes simplex virus type 1-encoded ICP0</prot>, the only well-conserved domain between the proteins is a zinc ring finger located near the amino terminus of both proteins. Our previous studies demonstrated that <prot>bICP0</prot> is toxic to transfected cells but does not appear to directly induce apoptosis (Inman, M., Y. Zhang, V. Geiser, and C. Jones, J. Gen. Virol. 82:483-492, 2001). C-terminal sequences in the last 320 amino acids of <prot>bICP0</prot> mediate subcellular localization. Mutagenesis of the zinc ring finger within <prot>bICP0</prot> revealed that this domain was important for transcriptional activation. In this study, we demonstrate that <prot>bICP0</prot> interacts with <prot>histone deacetylase 1</prot> (<prot>HDAC1</prot>), which results in activation of a simple promoter containing four consensus Myc-Max binding sites. The interaction between <prot>bICP0</prot> and <prot>HDAC1</prot> correlated with inhibition of Mad-dependent transcriptional repression. In resting CV-1 cells, <prot>bICP0</prot> relieved HDAC1-mediated transcriptional repression. The zinc ring finger was required for relieving HDAC1-induced repression but not for interacting with <prot>HDAC1</prot>. In fetal bovine lung cells but not in a human epithelial cell line, <prot>bICP0</prot> expression correlated with reduced steady-state levels of <prot>HDAC1</prot> in crude cytoplasmic extracts. We hypothesize that the ability of <prot>bICP0</prot> to overcome HDAC1-induced repression plays a role in promoting productive infection in highly differentiated cell types.</AbstractText>
