Concatemers in DNA replication: Electron microscopic studies of partially denatured intracellular lambda DNA

Skalka, Anna Marie; Poonian, Mohindar S.; Bartl, P.

doi:10.1016/0022-2836(72)90081-2

Cited by 85 publications

(20 citation statements)

References 12 publications

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“…Such complexes contribute to the activity of homologous recombination with linear dsDNA and are independent of the host recombination proteins (43). Homologous recombination has been proposed to be one of the pathways for generating substrates with the correct topology (genomic concatemers) for packaging into infectious viral particles (44).…”

Section: Resultsmentioning

confidence: 99%

Molecular Characterization of a Novel Temperate Sinorhizobium Bacteriophage, ФLM21, Encoding DNA Methyltransferase with CcrM-Like Specificity

Dziewit

Oscik

Bartosik

et al. 2014

J Virol

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ABSTRACT⌽LM21 is a temperate phage isolated from Sinorhizobium sp. strain LM21 (Alphaproteobacteria). Genomic analysis and electron microscopy suggested that ⌽LM21 is a member of the family Siphoviridae. The phage has an isometric head and a long noncontractile tail. The genome of ⌽LM21 has 50,827 bp of linear double-stranded DNA encoding 72 putative proteins, including proteins responsible for the assembly of the phage particles, DNA packaging, transcription, replication, and lysis. Virion proteins were characterized using mass spectrometry, leading to the identification of the major capsid and tail components, tape measure, and a putative portal protein. We have confirmed the activity of two gene products, a lytic enzyme (a putative chitinase) and a DNA methyltransferase, sharing sequence specificity with the cell cycle-regulating methyltransferase (CcrM) of the bacterial host. Interestingly, the genome of Sinorhizobium phage ⌽LM21 shows very limited similarity to other known phage genome sequences and is thus considered unique. IMPORTANCEProphages are known to play an important role in the genomic diversification of bacteria via horizontal gene transfer. The influence of prophages on pathogenic bacteria is very well documented. However, our knowledge of the overall impact of prophages on the survival of their lysogenic, nonpathogenic bacterial hosts is still limited. In particular, information on prophages of the agronomically important Sinorhizobium species is scarce. In this study, we describe the isolation and molecular characterization of a novel temperate bacteriophage, ⌽LM21, of Sinorhizobium sp. LM21. Since we have not found any similar sequences, we propose that this bacteriophage is a novel species. We conducted a functional analysis of selected proteins. We have demonstrated that the phage DNA methyltransferase has the same sequence specificity as the cell cycle-regulating methyltransferase CcrM of its host. We point out that this phenomenon of mimicking the host regulatory mechanisms by viruses is quite common in bacteriophages.

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Section: Resultsmentioning

confidence: 99%

Molecular Characterization of a Novel Temperate Sinorhizobium Bacteriophage, ФLM21, Encoding DNA Methyltransferase with CcrM-Like Specificity

Dziewit

Oscik

Bartosik

et al. 2014

J Virol

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“…3) (see below). However, efforts to show that Ter is a simple nuclease were confounded by the connection between cleavage and packaging: cells infected by mutants with mutations in any of the phage genes required for packaging accumulated linear concatemers (oligomers of several chromosomes joined head to tail) rather than single chromosomes with cohesive ends (45,183,194). Elegant studies of DNA packaging in vivo by using phage mutants that contain a short tandem cos duplication ruled out the possibility that Ter acts as a simple nuclease in vivo (54,56,57).…”

Section: Prophage Insertionmentioning

confidence: 99%

Little Lambda, Who Made Thee?

Gottesman

Weisberg

2004

Microbiol Mol Biol Rev

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SUMMARY The study of the bacteriophage λ has been critical to the discipline of molecular biology. It was the source of key discoveries in the mechanisms of, among other processes, gene regulation, recombination, and transcription initiation and termination. We trace here the events surrounding these findings and draw on the recollections of the participants. We show how a particular atmosphere of interactions among creative scientists yielded spectacular insights into how living things work.

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“…Late during bacteriophage vegetative growth, DNA replication results in the formation of linear concatemers consisting of genomes covalently joined head to tail (Smith and Skalka, 1966;Salzman and Weissbach, 1967;Carter et al, 1969;MacKinlay and Kaiser, 1969;Carter and Smith, 1970;Skalka et al, 1972;Wake et al, 1972;Enquist and Skalka, 1973;Better and Friefelder, 1983). In a process called DNA maturation, chromosomal units are cut from the concatemer by the introduction of two nicks, staggered 12 nucleotides apart on the opposite strands of the duplex, at a specific site in the DNA called cos (Enquist and Skalka, 1973;Feiss and Margulies, 1973;Emmons, 1974;Feiss and Campbell, 1974;Better and Freifelder, 1983).…”

Section: Introductionmentioning

confidence: 99%

Mutations of the coat protein gene of bacteriophage λ that overcome the necessity for the FI gene; the EFi domain

Murialdo

Tzamtzis

1997

Molecular Microbiology

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SummaryThe functions of most of the 10 genes involved in phage capsid morphogenesis are well understood. The function of the FI gene is one of the exceptions. Mutants in FI fail to mature and package DNA. The gene product (gpFI) seems to act as a catalyst for the formation of an intermediate in capsid assembly called complex II, which contains a procapsid (an empty capsid precursor), terminase (the enzyme that cleaves the DNA precursor and packages it into the procapsid) and DNA. The mechanism for this stimulation remains unknown. It has also been reported that gpFI appeared to stimulate terminase-mediated cos cleavage, in the absence of procapsids, by increasing enzyme turnover. In comparison with other head-gene mutants, FI mutants are leaky, producing approx. 0.1 phage per infected cell. Some second-site revertants of FI ¹ phages, called 'fin', that bypass the necessity for gpFI, have been isolated and found to harbour a mutation in the genes that code for the two subunits of terminase. In the course of mapping additional fin mutants, it was discovered that some mapped outside the terminase genes. To localize the mutations, restriction fragments of fin mutant DNAs were subcloned into plasmids and their ability to contribute to fin function was determined by marker-rescue analysis. The location of the fin mutation was further delineated by deletion analysis of a plasmid that was positive for fin. This showed that some fin mutations mapped to a region comprising genes E, D and a portion of C. The sequencing of this entire region in several fin isolates showed that the fin mutations are clustered in a small region of gene E corresponding to a portion of 26 amino acid residues of the coat protein (gpE ). We have called this region of the protein the EFi domain.All the mutations result in an increase in positive charge relative to the wild-type protein. These results suggest that DNA maturation and packaging are in part controlled by an interaction between gpFI and capsid gpE.

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Concatemers in DNA replication: Electron microscopic studies of partially denatured intracellular lambda DNA

Cited by 85 publications

References 12 publications

Molecular Characterization of a Novel Temperate Sinorhizobium Bacteriophage, ФLM21, Encoding DNA Methyltransferase with CcrM-Like Specificity

Molecular Characterization of a Novel Temperate Sinorhizobium Bacteriophage, ФLM21, Encoding DNA Methyltransferase with CcrM-Like Specificity

Little Lambda, Who Made Thee?

Mutations of the coat protein gene of bacteriophage λ that overcome the necessity for the FI gene; the EFi domain

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