Vales L D, Darnell J E
Rockefeller University, New York, New York 10021.
Genes Dev. 1989 Jan;3(1):49-59. doi: 10.1101/gad.3.1.49.
The left end of the adenovirus genome is arranged such that the polypeptide IX gene is 'buried' (entirely contained) within the E1B transcription unit. The E1B gene is transcribed actively early in infection while, in contrast, IX gene transcription only occurs after DNA replication. Using recombinant plasmid constructs and recombinant viruses, we have found that the nested arrangement of the IX gene prevents its transcription. The experiments show that E1B transcription across the IX promoter inhibits IX gene expression early in infection, and yet, the 21-kD E1B protein activates the IX gene. IX mRNA synthesis occurs in the absence of DNA replication when the E1A gene and E1B promoter are absent, but only when the 21-kD E1B protein is present in trans. Our results indicate that during the adenovirus infectious cycle, the only templates on which IX transcription can be activated are newly replicated templates not committed to E1B transcription. This situation may be a model for genes that are activated specifically at the time of replication.
腺病毒基因组的左端排列方式使得多肽IX基因“被掩埋”（完全包含）在E1B转录单元内。E1B基因在感染早期活跃转录，而相比之下，IX基因转录仅在DNA复制后发生。利用重组质粒构建体和重组病毒，我们发现IX基因的嵌套排列阻止了其转录。实验表明，E1B转录跨越IX启动子在感染早期抑制IX基因表达，然而，21-kD E1B蛋白却能激活IX基因。当E1A基因和E1B启动子缺失时，在没有DNA复制的情况下会发生IX mRNA合成，但前提是反式存在21-kD E1B蛋白。我们的结果表明，在腺病毒感染周期中，IX转录能够被激活的唯一模板是未用于E1B转录的新复制模板。这种情况可能是复制时特异性激活基因的一个模型。
