期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1978
卷号：75
期号：2
页码：605-609
DOI：10.1073/pnas.75.2.605
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：We have monitored the development of intracellular phiX DNA forms during the course of a virus life cycle that duplicates as closely as possible the normal infection of individual cells by single virions. The viral DNA was isolated in a one-step purification procedure, and quantitative electron microscopy was performed on the samples, resulting in the following conclusions: (i) Early in the life cycle, when the cells accumulate duplex rings, two types of DNA replication intermediates are observed: a rolling circle with a single-stranded tail; and a novel form, a single-stranded circle that is partially duplex. Thus, duplex ring synthesis appears to occur in two asymmetric steps, with positive strand DNA first being processed from the tail of the rolling circle and circularized, before it acts as a template for negative strand synthesis. (ii) Late in the life cycle, as single-stranded circles are synthesized and virus particles are assembled, only one replicating intermediate is observed--the rolling circle with a single-stranded tail. At this stage, the number of rolling circles reaches a level of about 35 per cell. (iii) The net rate of polymerization in the rolling circle intermediates is about 200 nucleotides per sec.
