scholarly journals Genetic Evidence for the Requirement of RecA Loading Activity in SOS Induction after UV Irradiation in Escherichia coli

2006 ◽  
Vol 188 (14) ◽  
pp. 5024-5032 ◽  
Author(s):  
Ivana Ivančić-Baće ◽  
Ignacija Vlašić ◽  
Erika Salaj-Šmic ◽  
Krunoslav Brčić-Kostić
Keyword(s):  
Escherichia Coli ◽  
Uv Irradiation ◽  
Constitutive Expression ◽  
Recq Helicase ◽  
Sos Induction ◽  
Dna Damaging Agents ◽  
Lexa Repressor ◽  
Recbcd Enzyme ◽  
Dna Substrate

ABSTRACT The SOS response in Escherichia coli results in the coordinately induced expression of more than 40 genes which occurs when cells are treated with DNA-damaging agents. This response is dependent on RecA (coprotease), LexA (repressor), and the presence of single-stranded DNA (ssDNA). A prerequisite for SOS induction is the formation of a RecA-ssDNA filament. Depending on the DNA substrate, the RecA-ssDNA filament is produced by either RecBCD, RecFOR, or a hybrid recombination mechansim with specific enzyme activities, including helicase, exonuclease, and RecA loading. In this study we examined the role of RecA loading activity in SOS induction after UV irradiation. We performed a genetic analysis of SOS induction in strains with a mutation which eliminates RecA loading activity in the RecBCD enzyme (recB1080 allele). We found that RecA loading activity is essential for SOS induction. In the recB1080 mutant RecQ helicase is not important, whereas RecJ nuclease slightly decreases SOS induction after UV irradiation. In addition, we found that the recB1080 mutant exhibited constitutive expression of the SOS regulon. Surprisingly, this constitutive SOS expression was dependent on the RecJ protein but not on RecFOR, implying that there is a different mechanism of RecA loading for constitutive SOS expression.

scholarly journals Effects of recJ, recQ, and recFOR Mutations on Recombination in Nuclease-Deficient recB recD Double Mutants of Escherichia coli

2005 ◽  
Vol 187 (4) ◽  
pp. 1350-1356 ◽  
Author(s):  
Ivana Ivančić-Baće ◽  
Erika Salaj-Šmic ◽  
Krunoslav Brčić-Kostić
Keyword(s):  
Escherichia Coli ◽  
Double Mutant ◽  
Reca Protein ◽  
Recq Helicase ◽  
Single Stranded Dna ◽  
Double Stranded Dna ◽  
Recf Pathway ◽  
Recombination Pathway ◽  
Recbcd Enzyme ◽  
Dna Ends

ABSTRACT The two main recombination pathways in Escherichia coli (RecBCD and RecF) have different recombination machineries that act independently in the initiation of recombination. Three essential enzymatic activities are required for early recombinational processing of double-stranded DNA ends and breaks: a helicase, a 5′→3′ exonuclease, and loading of RecA protein onto single-stranded DNA tails. The RecBCD enzyme performs all of these activities, whereas the recombination machinery of the RecF pathway consists of RecQ (helicase), RecJ (5′→3′ exonuclease), and RecFOR (RecA-single-stranded DNA filament formation). The recombination pathway operating in recB (nuclease-deficient) mutants is a hybrid because it includes elements of both the RecBCD and RecF recombination machineries. In this study, genetic analysis of recombination in a recB (nuclease-deficient) recD double mutant was performed. We show that conjugational recombination and DNA repair after UV and gamma irradiation in this mutant are highly dependent on recJ, partially dependent on recFOR, and independent of recQ. These results suggest that the recombination pathway operating in a nuclease-deficient recB recD double mutant is also a hybrid. We propose that the helicase and RecA loading activities belong to the RecBCD recombination machinery, while the RecJ-mediated 5′→3′ exonuclease is an element of the RecF recombination machinery.

Role of Escherichia coli RecBC enzyme in SOS induction

1985 ◽  
Vol 201 (3) ◽  
pp. 525-528 ◽  
Author(s):  
Abdul M. Chaudhury ◽  
Gerald R. Smith
Keyword(s):  
Escherichia Coli ◽  
Sos Induction

The role of thiol redox systems in the response of Escherichia coli to far-UV irradiation

Microbiology ◽  
2009 ◽  
Vol 78 (3) ◽  
pp. 290-295
Author(s):  
O. N. Oktyabr’skii ◽  
V. Yu. Ushakov ◽  
N. G. Muzyka ◽  
G. V. Smirnova
Keyword(s):  
Escherichia Coli ◽  
Uv Irradiation ◽  
Redox Systems ◽  
Thiol Redox

scholarly journals Role of DNA Ligase in the Illegitimate Recombination That Generates λbio-Transducing Phages in Escherichia coli

Genetics ◽  
2001 ◽  
Vol 158 (1) ◽  
pp. 29-39
Author(s):  
Masaaki Onda ◽  
Junko Yamaguchi ◽  
Katsuhiro Hanada ◽  
Yasuo Asami ◽  
Hideo Ikeda
Keyword(s):  
Escherichia Coli ◽  
Uv Irradiation ◽  
Sequence Homology ◽  
Illegitimate Recombination ◽  
Dna Ligase ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Recombinant Phage ◽  
Dna Break

Abstract We studied the role of DNA ligase in illegitimate recombination in Escherichia coli. A temperature-sensitive mutation in the lig gene reduced the frequency with which λbio-transducing phages were generated to 10-14% of that of wild type under UV irradiation. Reintroduction of the lig gene into this mutant restored the frequency of recombinant phage generation to that of wild type. Furthermore, overexpression of DNA ligase enhanced illegitimate recombination by 10-fold with or without UV irradiation. In addition, when DNA ligase was present in only limited amounts, UV-induced or spontaneous illegitimate recombination occurred exclusively at hotspot sites that have relatively long sequences of homology (9 or 13 bp). However, when DNA ligase was overexpressed, most of the illegitimate recombination took place at non-hotspot sites having only short sequences of homology (<4 bp). Thus, the level of ligase activity affects the frequency of illegitimate recombination, the length of sequence homology at the recombination sites, and the preference for recombination at hotspots, at least after UV irradiation. These observations support our hypothesis that the illegitimate recombination that generates λbio-transducing phages is mediated by the DNA break-and-join mechanism.

scholarly journals Role of RcsF in Signaling to the Rcs Phosphorelay Pathway in Escherichia coli

2005 ◽  
Vol 187 (19) ◽  
pp. 6770-6778 ◽  
Author(s):  
Nadim Majdalani ◽  
Michael Heck ◽  
Valerie Stout ◽  
Susan Gottesman
Keyword(s):  
Escherichia Coli ◽  
Cell Surface ◽  
Small Rna ◽  
Kinase Activity ◽  
Response Regulator ◽  
Constitutive Expression ◽  
Activation Mechanism ◽  
Sensor Kinase ◽  
High Level

ABSTRACT The rcs phosphorelay pathway components were originally identified as regulators of capsule synthesis. In addition to the transmembrane sensor kinase RcsC, the RcsA coregulator, and the response regulator RcsB, two new components have been characterized, RcsD and RcsF. RcsD, the product of the yojN gene, now renamed rcsD, acts as a phosphorelay between RcsC and RcsB. Transcription of genes for capsule synthesis (cps) requires both RcsA and RcsB; transcription of other promoters, including that for the small RNA RprA, requires only RcsB. RcsF was described as an alternative sensor kinase for RcsB. We have examined the role of RcsF in the activation of both the rprA and cps promoters. We find that a number of signals that lead to activation of the phosphorelay require both RcsF and RcsC; epistasis experiments place RcsF upstream of RcsC. The RcsF sequence is characteristic of lipoproteins, consistent with a role in sensing cell surface perturbation and transmitting this signal to RcsC. Activation of RcsF does not require increased transcription of the gene, suggesting that modification of the RcsF protein may act as an activating signal. Signals from RcsC require RcsD to activate RcsB. Sequencing of an rcsC allele, rcsC137, that leads to high-level constitutive expression of both cps and rprA suggests that the response regulator domain of RcsC plays a role in negatively regulating the kinase activity of RcsC. The phosphorelay and the variation in the activation mechanism (dependent upon or independent of RcsA) provide multiple steps for modulating the output from this system.

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