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：1980
卷号：77
期号：11
页码：6744-6748
DOI：10.1073/pnas.77.11.6744
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：We have constructed a plaque-forming hybrid phage, lambda SN4, which behaves as a composite replicon of the lambda phage and a mini-ColE1 plasmid. From the hybrid phage, plaque-type mutants altered in the ability to replicate as a ColE1 replicon were isolated. These mutations were designated as cer, signifying ColE1 replication defective. One of such mutants, lambda SN4cer6, was studied further. The mutant DNA was unable to replicate in vivo if expression and function of its lambda replicon were inhibited. The defect could not be complemented in trans. DNA sequence determination of the mutant phage revealed a single base pair (bp) alteration, C-G to T-A, at 160 bp upstream from the ori site of its ColE1 replicon. From lambda SN4cer6, revertants were obtained that had regained function of the ColE1 replicon, and they could be classified into two groups that showed a full and a partial recovery in the rates of ColE1-driven DNA synthesis. DNA sequence determination of revertant DNA indicated that the former group contained true revertants, T-A to C-G, at the cer6 site, whereas one of the partial revertants was found to sustain a secondary-site mutation, G-C to A-T at 187 bp upstream of the ori site. It was possible to construct a hairpin structure that starts by hydrogen bonding of bases at the site -160 and -187.
