Strategies of Bacteriophage DNA Replication

Relations Between Replication and Transcription

“…Similar to the case of phage λ replication where transcription from the P R promoter induces opening of the DNA under the same conditions (Keppel 1988). It was also suggested that RNAP involvement was not due to priming activity because transcription terminated by incorporation of 3'-dATP had no effect on replication initiation, meaning that there is no need for the transcript to cross the oriC sequence.…”

Evidence that the hanA gene coding for HU protein is essential for heterocyst differentiation in, and cyanophage A-4(L) sensitivity of, Anabaena sp. strain PCC 7120

“…The differential effect of a hanA mutation on sensitivity to A-1(L) and A-4(L) may be due to an ability of A-1(L) to code for a functionally similar protein, as does phage SPO1 of B. subtilis (26), or may reflect the differences in the strategies of DNA replication in these phages. The DNA in virulent phage A-1(L) is circularly permuted (3) and probably replicates via concatemeric intermediates (36), whereas the DNA in temperate phage A-4(L) has unique ends (3) and upon injection circularizes through recombination between terminal repeats that are present in virion DNA (38). For A-4(L), site-specific recombination could be required at the time of DNA circularization or at some stage of DNA replication.…”

Independence of bacteriophage N15 lytic and linear plasmid replication from the heat shock proteins DnaJ, DnaK, and GrpE

“…Although the mechanism of this regulation in E. coli (9) and some eukaryotes (28) has been explored, the functions of the heat shock proteins are not fully understood. Previous experiments have shown that the members of a subset of the heat shock proteins, composed of the dnaJ, dnaK, and grpE gene products, participate in the replication of some low-copy-number plasmids (4,5,13,23,27) and phages (14). In the low-copy-number plasmid P1, the DnaK and DnaJ proteins activate the specific DNA binding function of the essential plasmid replication protein, RepA, by converting it from dimers to monomers (26,27).…”

“…In bacteriophage X DNA replication, DnaK, DnaJ, and GrpE allow the release of the host DnaB protein from the phage P protein, allowing origin opening. Other temperate phages encode their own DnaB analogs and do not require the three heat shock proteins for their replication (14). The roles of these three and other heat shock proteins appear to be in the assembly and disassembly of multiprotein complexes, both facilitating appropriate interactions and preventing inappropriate ones (7).…”

“…Since mutations in the dnaJ, dnaK, and grpE genes block the vegetative growth of bacteriophage A and related phages (14), I tested to see whether N15 growth was normal in such mutants. The wild-type bacteriophage N15 used was derived from an E. coli C strain lysogenic for the phage (Table 1).…”