Studies on transcription controls operating in archaeal virus-host systems: regulation of transcription of genomes of the rudiviruses SIRV1 and SIRV2, and the lipothrixvirus SIFV of the hyperthermophilic archaeaon Sulfolobus

一对杆状病毒SIRV 1和SIRV 2的超嗜热硫化叶菌，其基因组最近已被完全测序，是一个有吸引力的和独特的模式，解开机制，控制和信号结构参与的基因表达在Escherea。病毒SIRV 1通过在基因组中广泛和快速积累点突变以DNA病毒不寻常的方式响应宿主的变化。这允许快速选择适应新宿主的新病毒变体，同时恢复复制的高保真度。与SIRV 1的基因组相反，SIRV 2的基因组与后者高度同源，但长3.2kb，在相同的宿主中保持不变。为了了解SIRV 1特异性突变系统及其控制，我们计划研究这两种病毒基因组的转录和复制。对SIRV 1和SIRV 2基因组在不同宿主中的转录本进行比较研究，将使我们能够确定参与对宿主物种变化的反应的候选基因，以及在这种条件下引起病毒行为差异的候选基因。通过构建由两种病毒基因组的不同部分组成的重组DNA分子，以不影响基本病毒功能的方式，这些基因将被选择性地破坏，或从病毒DNA中删除/引入病毒DNA中。用这些DNA转染合适的宿主并研究其复制和转录将有助于阐明基因编码的蛋白质的功能及其表达调控。这些研究还将能够鉴定对病毒功能非必需的ORF，并为基于病毒DNA的转化载体的开发奠定基础。

A pair of rod-shaped viruses SIRV1 and SIRV2 of hyperthermophilic Sulfolobus, the genomes of which have been recently completely sequenced, is an attractive and unique model for unravelling mechanisms, controls and signal structures involved in gene expression in Archaea. The virus SIRV1 responds to changes of a host in a way unusual for DNA viruses by extensive and rapid accumulation of point mutations in the genome. This allows rapid selection of new virus variants adapted to a new host, coinciding with a recovery of high fidelity of replication. In contrast to the genome of SIRV1, the genome of SIRV2, which is highly homologous to the latter, however, 3.2 kb longer, remains unchanged in the same hosts. In order to understand the SIRV1-specific mutator system and its control we plan to study transcription and replication of the genomes of the two viruses. Comparative studies of transcripts of the genomes of SIRV1 and SIRV2 in different hosts will enable us to identify candidate genes that are involved in a response to changes of host species, and those which cause differences in the behaviour of the viruses under such conditions. These genes will be selectively disrupted, or deleted/introduced from/into the DNAs of the viruses by constructing recombinant DNA molecules consisting of different portions of the genomes of the two viruses in a way not affecting essential viral functions. Transfection of an appropriate host with these DNAs and studies on their replication and transcription will shed light on functions of proteins encoded by the genes and controls of their expression. The studies will also enable to identify ORFs which are nonessential for virus function, and lay the basis for the development of a transformation vector based on the virus DNAs.