Varicella Zoster Virus Transcriptional Regulation and the Roles of VZV IE Proteins
Jeffrey I. Cohen
from: Alphaherpesviruses: Molecular Virology (Edited by: Sandra K. Weller). Caister Academic Press, U.K. (2011)
Varicella-zoster virus (VZV) encodes three immediate-early proteins, IE4, IE62, and IE63; however, only IE62 has TAATGARAT-like sequences in its promoter which are present in the promoters of each of the herpes simplex virus immediate-early proteins. The TAATGARAT-like elements on the IE62 promoter bind to VZV ORF10 protein, Oct, and HCF-1. In addition, histone methyltransferases are recruited to the IE62 promoter to modify chromatin to a transcriptionally active form. VZV IE62, the major VZV transactivator binds to VZV IE4 and IE63, and Med25, part of the mediator complex which upregulates gene expression. VZV IE62, IE4, and IE63 are present in the viral tegument where they may help to regulate transcription early in infection. IE63 binds to several cellular proteins including ASF1 and RNA polymerase II. Two hypotheses have been proposed for regulation of VZV gene expression during latency. First, relocalization of HCF-1 from the cytoplasm to the nucleus of sensory ganglia in response to stimuli associated with reactivation may help to augment transcription of IE62 to reactivate VZV from latency. Second, promoters of latent genes are maintained in a euchromatic state allowing their transcription, while promoters of genes not associated with latency are in a heterochromatic state resulting in repression of transcription read more ...