Characterization of the human cytomegalovirus UL75 (glycoprotein H) late gene promoter.

Glycoprotein H (gH, UL75) of human cytomegalovirus (HCMV) is an essential envelope glycoprotein that functions in viral entry and the activation of gene expression. To understand the regulation of this important viral gene, the promoter of the UL75 late gene was characterized in HCMV-infected cells at the late stages of viral infection. Primer extension analysis revealed a single major start site located 26 bp downstream of a putative TATA element. Deletion analysis showed the presence of a dominant activation domain from +14 to +35 that masked regulatory sequences upstream of the TATA element. Mutational analysis demonstrated that a PEA3-like element in this downstream domain was important for promoter activation. In addition, gel shift analysis revealed direct protein binding to the PEA3-like element. Together, these studies reveal that the gH promoter is regulated in a complex manner with sequences both upstream and downstream of the cap site influencing promoter activation.