Relative roles of T7 RNA polymerase and gene 4 primase for the initiation of T7 phage DNA replication in vivo.
- 1 June 1987
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences
- Vol. 84 (12), 3977-3981
- https://doi.org/10.1073/pnas.84.12.3977
Abstract
Initiation sites of T7 phage DNA replication in the presence and absence of T7 phage gene 4 primase have been analyzed by using Escherichia coli cells infected with T7 phage amber mutants, T73,6 and T73,4,6, respectively. Restriction analysis of the [3H]thymidine-labeled DNA, synthesized by the T73,4,6 phage-infected cells in the presence of 2'',3''-dideoxy-3''-azidothymidine, has shown that only the light (L) strand of T7 DNA has been synthesized from the primary origin area to the right. Transition sites from RNA to DNA have been located precisely in the primary origin region of the T7 phage genome. In the gene 4- condition, > 20 transition sites have been detected only in the L strand. They scattered widely down-stream from the .vphi.1.1 promoters and mostly downstream from the .vphi.1.3 promoter. The same transition sites have been detected in the gene 4+ condition, suggesting that the transcripts started from these promoters are used as primers of the rightward L-strand DNA synthesis in the gene 4+ condition. In addition, many heavy (H)- and L-strand transition sites have been detected at gene 4 primase sites in the gene 4+ condition. The relative roles of T7 phage RNA polymerase and primase at the primary origin have been discussed.Keywords
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