Bacteriophage Lambda; Abortive Infection of Bacteria Lysogenic for Phage P2

Lindahl, Gunnar; Sironi, Gianpiero; Bialy, Harvey; Calendar, Richard

doi:10.1073/pnas.66.3.587

Cited by 117 publications

(61 citation statements)

References 20 publications

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“…Prophage P2 expresses a gene, old, whose product is responsible for the inhibition of A growth (34). The action of old appears to be to introduce a general replication block in cells in which the function of RecBCD is impaired (20). Accordingly, P2 is unable to lysogenize a recB or recC mutant unless it bears a mutation in old, and A is unable to replicate in a P2 lysogen if it inactivates RecBCD by making Gam (20,34,42).…”

Section: Discussionmentioning

confidence: 99%

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Modulation of Escherichia coli RecBCD activity by the bacteriophage lambda Gam and P22 Abc functions

1988

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Plasmids that express the bacteriophage A gam gene or the P22 abc2 gene (with and without abcl) at controllable levels were placed in Escherichia coli and tested for effects on the activity of RecBCD. Like Gam, Abc2 inhibited the ATP-dependent exonuclease activity of RecBCD, apparently not by binding to DNA. However, Abc2-mediated inhibition was partial, while Gam-mediated inhibition was complete. Both Abc2 and Gam inhibited host system-mediated homologous recombination in a Chi-containing interval in the chromosome of a hybrid A phage; Abc2 inhibited it more strongly than Gam. Gam but not Abc2 spared a phage T4 gene 2 mutant from restriction by RecBCD; Abc2 exhibited weak sparing activity in combination with Abcl and substantial activity in combination with both Abcl and the P22 homologous recombination function Erf. Either Gam or the combination of the A recombination functions Exo and Bet was sufficient to induce a mode of plasmid replication that produced linear multimers. The combination of Abc2, Abcl, and Erf also exhibited this activity. However, Erf was inactive, both by itself and in combination with Abcl; Abc2 had weak activity. These results indicate that Gam and Abc2 modulate the activity of RecBCD in significantly different ways. In comparison with A Gam, P22 Abc2 has a weak effect on RecBCD nuclease activity but a strong effect on its recombination-promoting activity.The RecBCD enzyme of Escherichia coli catalyzes exonucleolytic degradation of DNA and promotes homologous recombination. To a certain extent, these two activities are distinct; while recB and recC mutants lack both, recD mutants lack only the nuclease (1, 6). The presence of RecBCD nuclease in the cell inhibits rolling-circle replication of such diverse replicons as phage X and plasmid ColEl, possibly because a critical part of the rolling circle is susceptible to exonucleolytic degradation (9,12,35). Accordingly, many bacteriophages, including X, T2, T3, T4, T5, T6, T7, P1, and 480, inhibit RecBCD nuclease during lytic growth (3, 24, 28). In addition to inhibiting rolling-circle replication, the RecBCD nuclease can degrade the linear DNA injected by some phages. Phage T4 virions contain a protein, the product of phage gene 2, that protects the phage chromosome from RecBCD; phage mutants lacking this function are restricted to growth in recBCD mutants (23 of RecBCD on lytic growth of the phage (13). Two adjacent genes, abcl and abc2, contribute independently to this function; abc2 makes the larger contribution (22). The abc2 gene, in particular, is analogous to the X gam gene in that it is required for growth of the phage in a polA host. However, the gam and abc genes differ in significant ways. They are not homologous. Moreover, they occupy different positions in the phage chromosome: the abc genes are located to the left of the homologous recombination-promoting erf gene, while gam is located to the right of the homologous recombination-promoting bet gene. This is the only known case in which the map order of analogous genetic elemen...

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Section: Discussionmentioning

confidence: 99%

“…The answer may have to do with host range. In E. coli lysogenic for phage P2, A does not grow (20), while a A hybrid bearing a substitution of the P22 erf region for the A red region does (17). Prophage P2 expresses a gene, old, whose product is responsible for the inhibition of A growth (34).…”

Section: Discussionmentioning

confidence: 99%

Modulation of Escherichia coli RecBCD activity by the bacteriophage lambda Gam and P22 Abc functions

1988

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“…The P2 old gene product interferes with the growth of λ phage and kills E. coli cells that lack the recBCD nuclease-helicase. 75 Induction of λ prophage in a P2 old C -lysogenic strain results in partial degradation of many tRNA molecules. 76 Purified Old protein has been reported to have 5 0 to 3 0 exonuclease activity on DNA, as well as an uncharacterized ribonuclease activity.…”

Section: Accessory Genes ("Morons")mentioning

confidence: 99%

Bacteriophage P2

Christie

Calendar

2016

Bacteriophage

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“…Recombination between the oligonucleotide and the infecting phage inactivated gam and allowed selection for the desired red gam mutants on a P2 lysogen of strain C600 (LINDAHL et al 1970;ZISSLER et al 1971).…”

Section: Bacteriophage  Construction By Recombineeringmentioning

confidence: 99%

RecBCD Enzyme “Chi Recognition” Mutants Recognize Chi Recombination Hotspots in the Right DNA Context

2016

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RecBCD enzyme is a complex, three-subunit protein machine essential for the major pathway of DNA double-strand break repair and homologous recombination in Escherichia coli. Upon encountering a Chi recombination-hotspot during DNA unwinding, RecBCD nicks DNA to produce a single-stranded DNA end onto which it loads RecA protein. Conformational changes that regulate RecBCD's helicase and nuclease activities are induced upon its interaction with Chi, defined historically as 59 GCTGGTGG 39. Chi is thought to be recognized as single-stranded DNA passing through a tunnel in RecC. To define the Chi recognition-domain in RecC and thus the mechanism of the RecBCD-Chi interaction, we altered by random mutagenesis eight RecC amino acids lining the tunnel. We screened for loss of Chi activity with Chi at one site in bacteriophage l. The 25 recC mutants analyzed thoroughly had undetectable or strongly reduced Chi-hotspot activity with previously reported Chi sites. Remarkably, most of these mutants had readily detectable, and some nearly wild-type, activity with Chi at newly generated Chi sites. Like wild-type RecBCD, these mutants had Chi activity that responded dramatically (up to fivefold, equivalent to Chi's hotspot activity) to nucleotide changes flanking 59 GCTGGTGG 39. Thus, these and previously published RecC mutants thought to be Chi-recognition mutants are actually Chi context-dependence mutants. Our results fundamentally alter the view that Chi is a simple 8-bp sequence recognized by the RecC tunnel. We propose that Chi hotspots have dual nucleotide sequence interactions, with both the RecC tunnel and the RecB nuclease domain.KEYWORDS chromosomal sites; recombination hotspots; Chi; RecBCD enzyme; DNA context-dependence H OMOLOGOUS recombination, like other aspects of chromosome metabolism, is controlled by special DNA sites. The sites controlling homologous recombination that are best understood at the molecular level are the Chi hotspots of Escherichia coli (Smith 2012). Chi sites control RecBCD enzyme, a complex enzyme with both nuclease and helicase activities essential for the major pathway of DNA double-strand break repair and genetic recombination. These sites, called Chi for crossover hotspot instigator (Lam et al. 1974), locally stimulate recombination by altering the multiple activities of RecBCD. Here, we address the question of how RecBCD recognizes Chi, the first step in its stimulation of recombination. Our results force a reanalysis of both the Chi nucleotide sequence and how RecBCD recognizes Chi.Chi was discovered as a set of mutations that increase the plaque size of phage l red gam mutants, which rely on the E. coli RecBCD pathway for growth (Lam et al. 1974;McMilin et al. 1974;Henderson and Weil 1975). In the absence of its own recombination functions (Red) and of the RecBCD inhibitor (Gam), l replication forms only monomeric circles. Phage DNA packaging, however, requires dimeric or higher order concatemers, which can be formed by RecBCDpromoted recombination between monomers. Wild-typ...

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Bacteriophage Lambda; Abortive Infection of Bacteria Lysogenic for Phage P2

Cited by 117 publications

References 20 publications

Modulation of Escherichia coli RecBCD activity by the bacteriophage lambda Gam and P22 Abc functions

Modulation of Escherichia coli RecBCD activity by the bacteriophage lambda Gam and P22 Abc functions

Bacteriophage P2

RecBCD Enzyme “Chi Recognition” Mutants Recognize Chi Recombination Hotspots in the Right DNA Context

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