Regulation Of Virus Gene Expression and DNA Replication

痘病毒编码在感染细胞的细胞质内转录和复制其基因组所需的酶和因子。痘苗病毒是痘病毒家族的典型成员，它为研究基因调控、信使核糖核酸的生物合成和DNA复制机制提供了一种结合生化和遗传学方法的独特系统。对痘苗病毒的研究表明，这些基因分为三个时间类别-早期、中期和晚期。每个基因类都有一个一致的DNA启动子序列和相应的转录因子，这些转录因子与病毒编码的多亚单位RNA聚合酶相互作用。早期基因的转录系统在组装过程中被包装在感染性病毒颗粒内，而中晚期基因转录因子在感染后相继合成，DNA被合成为串联体，并在病毒组装过程中被包装成单位长度的基因组。

Poxviruses encode enzymes and factors needed for transcription and replication of their genomes within the cytoplasm of infected cells. Vaccinia virus, the prototypic member of the poxvirus family, provides a unique system for combining biochemical and genetic approaches for investigating mechanisms of gene regulation, mRNA biosynthesis, and DNA replication. Studies with vaccinia virus indicated that the genes are divided into three temporal classes - early, intermediate and late. Each gene class has a consensus DNA promoter sequence and corresponding transcription factors that interact with the virus-encoded multisubunit RNA polymerase. The transcription system for early genes is packaged within the infectious virus particle during its assembly, whereas the factors for intermediate and late gene transcription are synthesized successively after infection.The DNA is synthesized as concatemers that are resolved into unit length genomes and packaged during virus assembly.