Transcription fromVaricella-Zoster VirusGene67 (Glycoprotein IV)

Threetranscripts map tothevaricella-zoster virus (VZV)open reading frame(ORF)67,whichencodes glycoprotein IV(gplV). Allofthese transcripts are polyadenylated andare transcribed fromleft toright towards thegenomic terminal short repeats. Previous Northern (RNA)blot analysessuggested thatthemost abundant ofthese transcripts (1.65 kb)might codeforgpIV. We performed Sinuclease protection andprimer extension assaysanddetermined thatthe5'terminus ofthe1.65-kb transcript maps 91bpupstream fromthe gpIVinitiation codon. AnAT-rich region (ATAAA), -28bpfromthecapsite, isa potential TATA box,and at-71bpthere isa consensusCCAAT boxmotif. The3'endofthe1.65-kb transcript is20bpdownstream oftwooverlapping polyadenylation signals, AATAAA andATTAAA,andjust downstream ofthe3'terminus isaGU-rich sequence.These results arereminiscent ofdatafromouranalysis oftheVZVgpVgene,confirming thatVZV appearsabletouse unusual TATA boxmotifs. Manycanonical TATA sequencesare present upstreamfromthese VZV transcriptional startsites but,apparently, are notused.We tested sequences upstream fromthegpIVcapsite forpromoter activity intransient expression experiments bycloning a DNA fragment (+63to-343bp)into pCAT3M,whichcontains achloramphenicol acetyltransferase reporter gene. Thisclone showedlittle constitutive promoter activity butwas activated more than200-fold byinfection with VZV and5-fold withherpes simplex virus. ThetwoknownVZV transactivating genes(those forORF 4and ORF 62)were tested fortheir abilities toactivate expression fromthegpIVpromoter byusing their cognate promoters. TheORF 4gene was minimally active, whereas theORF 62gene gavetwofold induction; both genes,acting together, gave fivefold induction. However, replacement oftheIE62promoterwiththe immediate-early cytomegalovirus promoterintheORF 62construct gaveover40-fold induction ofchloramphenicol acetyltransferase activity underthegpIVpromoter inthesame assay. Varicella-zoster virus (VZV)isthecausative agent oftwo clinical exanthems. Varicella, commonly called chickenpox, causes amilddisease withfewcomplications andisusually contracted during childhood. Zoster, orshingles, caused by thereactivation oflatent virus, isapainful disease normally foundinolder individuals orimmunocompromised patients. Bothchickenpox andzoster areoccasionally serious or life-threatening, especially inimmunocompromised individ