Jenkins D E, Martens C L, Mocarski E S
Department of Microbiology and Immunology, Stanford University School of Medicine, California 94305-5402.
J Gen Virol. 1994 Sep;75 ( Pt 9):2337-48. doi: 10.1099/0022-1317-75-9-2337.
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 gamma IE2(338aa), a 40K late gene product, were more abundant than those encoding IE2(579aa), an alpha gene product made throughout infection. As expected, the cDNA capable of directing the expression of gamma IE2(338aa) was derived from a contiguous genomic region within exon 5 of the ie1/ie2 region. The cDNA clones encoding gamma IE2(338aa) and IE2(579aa) 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, gamma IE2(338aa) trans-activated a variety of test promoters when cotransfected with the major alpha gene product, IE1(491aa). Promoters derived from the cellular beta-actin gene, the simian virus 40 early region and the human immunodeficiency virus were all responsive to gamma IE2(338aa) plus IE1(491aa), although several beta 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 alpha gene expression.
为了研究人巨细胞病毒（HCMV）立即早期基因2（ie2）（UL122）在感染后期产生的基因产物的功能，从用感染后74小时的mRNA构建的表达文库中分离出cDNA克隆。基于对该文库的筛选，此时感染细胞中1%的转录本是ie2区域特异性的，编码γIE2（338个氨基酸）（一种40K晚期基因产物）的转录本比编码IE2（579个氨基酸）（一种在整个感染过程中产生的α基因产物）的转录本更丰富。正如预期的那样，能够指导γIE2（338个氨基酸）表达的cDNA来自ie1/ie2区域外显子5内的一个连续基因组区域。比较了编码γIE2（338个氨基酸）和IE2（579个氨基酸）的cDNA克隆在反式激活病毒和细胞启动子以及通过ie2顺式抑制信号抑制ie1/ie2启动子表达方面的能力。出乎意料的是，当与主要的α基因产物IE1（491个氨基酸）共转染时，γIE2（338个氨基酸）反式激活了多种测试启动子。来自细胞β-肌动蛋白基因、猿猴病毒40早期区域和人类免疫缺陷病毒的启动子都对γIE2（338个氨基酸）加IE1（491个氨基酸）有反应，尽管来自HCMV基因组的几个β启动子没有反应。因此，ie2区域这种丰富的晚期产物除了作为α基因表达的抑制剂外，可能在反式激活中也发挥作用。
