Cloning and transcriptional regulation of the DNA replication-processivity factor gene of human herpesvirus-6
Human herpesvirus 6 (HHV-6) is a T cell-tropic virus which may play a role in a number of lymphoproliferative disorders as well as in the progression of a human immunodeficiency virus (HIV) infection. A cDNA encoding a 41 kd nuclear antigen (p41) expressed at early times in HHV-6 infected cells was isolated by immunoscreening a cDNA expression library with an anti-p41 monoclonal antibody. p41 is virally encoded and is highly homologous (44% sequence identity) to ICP36 (UL44 gene product), the major late DNA binding protein of human cytomegalovirus (HCMV). p41 binds DNA with the same apparent affinity as ICP36 and since ICP36 has recently been shown to be a HCMV DNA polymerase-associated processivity factor, a similar function is suggested for p41. To elucidate how the p41 gene is transcriptionally regulated, its promoter was characterized. Three p41 specific RNA transcripts were identified in HHV-6 infected cells. A single transcription start site is located 48 bp upstream of the start codon of the p41 open reading frame and a functional TATA box is 26 bp upstream of this transcription start site. A reporter construct which contained the 1027 bp region upstream of the p41 start codon was inactive in uninfected cells but functioned as a strong promoter in HHV-6 infected T-cells. Mutational analysis identified an element (EA site) located $-$73 bp to $-$52 bp relative to the transcriptional start site which was required for the strong activity of the p41 promoter. The ability of the EA site to confer strong transcriptional activity was strictly dependent on its distance from the p41 basal promoter. The EA site contains three overlapping sequences, a C/EBP recognition site and two repeat elements. Two binding complexes, C1 and C2, specifically recognize the EA site in infected cells. These complexes as well as two additional binding complexes, C3 and C4, are present in uninfected cells. C3 and C4 complexes contain members of the C/EBP transcription factor family while the C1 and C2 complexes do not.
Thompson, James Richard, "Cloning and transcriptional regulation of the DNA replication-processivity factor gene of human herpesvirus-6" (1994). Dissertations available from ProQuest. AAI9427627.