Sun Yang, Qiao Xueying, Mindich Leonard
Department of Microbiology, The Public Health Research Institute, Newark, NJ 07103, USA.
Virology. 2004 Feb 20;319(2):274-9. doi: 10.1016/j.virol.2003.10.022.
The cystoviridae are bacteriophages with genomes of three segments of dsRNA enclosed within a polyhedral capsid. Two members of this family, Phi6 and Phi8, have been shown to form carrier states in which the virus replicates as a stable episome in the host bacterium while expressing reporter genes such as kanamycin resistance or lacalpha. The carrier state does not require the activity of all the genes necessary for phage production. It is possible to generate carrier states by infecting cells with virus or by electroporating nonreplicating plasmids containing cDNA copies of the viral genomes into the host cells. We have found that carrier states in both Phi6 and Phi8 can be formed at high frequency with all three genomic segments or with only the large and small segments. The large genomic segment codes for the proteins that constitute the inner core of the virus, which is the structure responsible for the packaging and replication of the genome. In Phi6, a carrier state can be formed with the large and middle segment if mutations occur in the gene for the major structural protein of the inner core. In Phi8, carrier state formation requires the activity of genes 8 and 12 of segment S.
囊病毒科是一种噬菌体，其基因组由三段双链RNA组成，包裹在一个多面体衣壳内。该家族的两个成员，Phi6和Phi8，已被证明能形成载体状态，即病毒在宿主细菌中作为稳定的附加体进行复制，同时表达如卡那霉素抗性或乳糖α等报告基因。载体状态并不需要噬菌体产生所需的所有基因的活性。通过用病毒感染细胞或通过电穿孔将含有病毒基因组cDNA拷贝的非复制性质粒导入宿主细胞，都有可能产生载体状态。我们发现，Phi6和Phi8中的载体状态都可以通过所有三个基因组片段或仅通过大片段和小片段以高频形成。大基因组片段编码构成病毒内核的蛋白质，该结构负责基因组的包装和复制。在Phi6中，如果内核主要结构蛋白的基因发生突变，则可以通过大片段和中片段形成载体状态。在Phi8中，载体状态的形成需要S片段的基因8和12的活性。
