RELATION BETWEEN BACTERIOPHAGE-T4 DNA-REPLICATION AND LATE TRANSCRIPTION INVITRO AND INVIVO

An in vitro system for DNA and late RNA synthesis in extracts of phage T4-infected Escherichia coli has been devised. Here we describe the DNA synthesis properties of the system, as derived from T4 wild type- or replication mutant-infected cells. When the system is prepared from wild type phage-infected cells, DNA synthesis in vitro is sustained for a longer time at 25 than at 37°; both dCMP and hmdCMP can be incorporated into DNA. When the system is derived from E. coli infected with replication-defective T4 mutants, DNA synthesis in vitro parallels, at least qualitatively, the in vivo replication properties of these infections. T4 late RNA synthesis in vitro, even that RNA synthesis which should be initiated in vitro, can occur in the absence of concurrent DNA synthesis, both at 25 and at 40°. Nevertheless, bacteria infected with a temperature-sensitive T4 DNA polymerase (gp 43) mutant, tsP36, generate cell-free systems with the property of temperature-sensitive T4 late RNA synthesis in the absence of concurrent DNA synthesis. Bacteria-infected with a temperature-sensitive T4 dCMP hydroxymethylase (gp 42) mutant, tsLB3, do not show a comparable temperature sensitivity. Stimulated by this finding, certain aspects of the connection between T4 DNA replication and late RNA synthesis in vivo have been analyzed (or reanalyzed) The quantitative and qualitative effects, on T4 late RNA synthesis, of blocking DNA synthesis with FUdR and of inactivating temperature-sensitive T4 DNA replication proteins (gp 42 and gp 43) are shown to differ. The outcome of these in vitro and in vivo experiments is consistent with the notion that at least some of the T4 DNA replication proteins interact with the late gene transcription system. © 1979.