Regulation of Poxvirus Gene Expression & 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。牛痘病毒是痘病毒家族的原型成员，它提供了一个独特的系统，用于结合生物化学和遗传学方法来研究基因调控、mRNA生物合成和DNA复制的机制。对牛痘病毒的研究表明，这些基因分为三个时间类别-早期、中期和晚期。每个基因类别都有一个共有的DNA启动子序列和相应的转录因子，与病毒编码的多亚基RNA聚合酶相互作用。早期基因的转录系统在病毒组装过程中被包装在病毒颗粒内，而中期和晚期基因转录因子在感染后相继合成。DNA合成为多联体，在病毒组装过程中被分解成单位长度的基因组并包装。

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.