IE2 protein is insufficient for transcriptional repression of the human cytomegalovirus US3 promoter

Abstract

Expression of the human cytomegalovirus (HCMV) US3 gene is regulated in part by transcriptional repression mediated through a cis-repressive region located between the TATA box and the transcriptional start site. The US3 cis-repressive element has extensive sequence identity with a similar repressive element in UL122-123 (the major immediate-early gene complex). Repression of UL122-123 is mediated through the interaction of the IE2 protein with cis-repressive sequences. In spite of the similarity of the two repressive elements, IE2 activated rather than repressed transcription from the US3 promoter. Additionally, IE1 or IE1 and IE2 in combination also activated US3 expression. These data demonstrate that regulation of HCMV immediate-early genes is quite complex and involves a number of proteins.