Abstract
In order to study the function of human cytomegalovirus (HCMV) immediate early gene 2 (ie2) (UL122) gene products made at late times during infection, cDNA clones were isolated from an expression library made with 74 h post-infection mRNA. Based on screening of the library, 1% of transcripts in infected cells at this time were ie2 region-specific, and transcripts encoding γIE2338aa, a 40K late gene product, were more abundant than those encoding IE2579aa, an α gene product made throughout infection. As expected, the cDNA capable of directing the expression of γIE2338aa was derived from a contiguous genomic region within exon 5 of the ie1/ie2 region. The cDNA clones encoding γIE2338aa and IE2579aa were compared for their ability to trans-activate viral and cellular promoters and to repress expression from the ie1/ie2 promoter via the ie2 cis-repression signal. Unexpectedly, γIE2338aa trans-activated a variety of test promoters when cotransfected with the major α gene product, IE1491aa. Promoters derived from the cellular -actin gene, the simian virus 40 early region and the human immunodeficiency virus were all responsive to γIE2338aa plus IE1491aa, although several promoters derived from the HCMV genome were unresponsive. Thus, this abundant late product from the ie2 region may play a role in trans-activation in addition to its role as a repressor of α gene expression.
† Present address: Affymax Research Institute, 4001 Miranda Avenue, Palo Alto, California 94304, U.S.A.