Escherichia coli RecX Inhibits RecA Recombinase and Coprotease Activities in Vitro and in Vivo

Stohl, Elizabeth A.; Brockman, Joel; Burkle, Kristin L.; Morimatsu, Katsumi; Kowalczykowski, Stephen C.; Seifert, H. Steven

doi:10.1074/jbc.m210496200

Cited by 170 publications

(182 citation statements)

References 42 publications

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“…The effect of RecX is actually greater where RecX protein is added to an experiment prior to RecA protein (52). The inhibition of RecA ATPase activity by RecX is greater in the presence of SSB than in the absence of SSB (58).…”

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confidence: 92%

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SSB Antagonizes RecX-RecA Interaction

Baitin

Gruenig

Cox

2008

Journal of Biological Chemistry

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The bacterial RecA protein is the prototype of a nearly ubiquitous class of recombinase proteins (1-11). These enzymes promote DNA strand exchange reactions that lie at the heart of all recombination and recombinational DNA repair processes (11-16). The recombinase forms a right-handed helical filament, usually on single-stranded DNA (ssDNA).2 A homologous duplex DNA is then aligned with this bound single strand, and one strand (the one complementary to the bound single strand) is transferred from the duplex substrate to form a new duplex within the filament. This process is used to reconstruct stalled replication forks, repair double strand breaks, facilitate meiotic cross-overs in eukaryotes, and facilitate genetic exchanges of many types in almost every organism. Typical reactions are illustrated in Fig. 1.The assembly and disassembly of RecA protein filaments on DNA has been studied in some detail, although understanding is not complete. Nucleation occurs most readily on ssDNA. There are discrete nucleation and extension phases in the assembly process, with extension proceeding primarily 5Ј to 3Ј relative to the ssDNA (17, 18). Disassembly also proceeds primarily 5Ј to 3Ј, with monomeric subunits being added on one end and subtracted from the other (19,20). Dissociation at the disassembly end is coupled to ATP hydrolysis (21,22).RecA-promoted reactions are important to cell viability. Escherichia coli strains lacking a functional recA gene are viable but highly sensitive to DNA-damaging agents (23-25). Recombinational DNA repair is thus important in bacteria, especially for the repair of stalled or collapsed replication forks (26 -30). However, recombination can also have deleterious consequences and must be regulated. Recombination between repeated sequences in the genome, for example, could result in the deletion of essential genes.In the past decade, multiple new RecA regulatory mechanisms have been elucidated. The expression of the recA gene is regulated as part of the SOS response (31-35). The native RecA protein is auto-regulated by the 17 amino acid residues at its own C terminus, because virtually every RecA activity is enhanced when those 17 amino acids are deleted (36 -41). Finally, RecA function is regulated by a growing array of regulatory proteins.There are at least eight proteins in a typical E. coli cell that modulate RecA protein function to some extent. Much of the regulation is focused on RecA filament assembly and disassembly. One modulator of RecA filament dynamics is SSB. SSB strongly inhibits the nucleation phase of RecA filament assembly (42) but stimulates the extension phase, removing secondary structure in ssDNA that would otherwise impede filament growth (43-46). Although ordinarily SSB protein prevents filament nucleation, single RecA monomers can easily be added to an existing filament and displace SSB from DNA at the rate of filament extension (47).Additional proteins affect other aspects of RecA protein filament function, often by interacting directly with RecA. The nucleation ...

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confidence: 92%

“…The RecX protein is the focus of the present report and an inhibitor of RecA function both in vivo and in vitro (58). Seifert and co-workers (58) demonstrated that RecA and RecX proteins physically interact using yeast two-hybrid analysis in E. coli.…”

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confidence: 99%

SSB Antagonizes RecX-RecA Interaction

Baitin

Gruenig

Cox

2008

Journal of Biological Chemistry

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“…RecX is a bacterial regulatory protein which acts as an anti-recombinase to quell inappropriate recombinational repair during normal DNA metabolism [122,123]. It is found in bacteria and some plants (Arabidopsis thaliana & Oryza sativa) but not in archaea.…”

Section: Methanobacterium Thermoformicium and Neisseria Gonorhoeaementioning

confidence: 99%

Phylogeny vs genome reshuffling: horizontal gene transfer

2008

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The evolutionary events in organisms can be tracked to the transfer of genetic material. The inheritance of genetic material among closely related organisms is a slow evolutionary process. On the other hand, the movement of genes among distantly related species can account for rapid evolution. The later process has been quite evident in the appearance of antibiotic resistance genes among human and animal pathogens. Phylogenetic trees based on such genes and those involved in metabolic activities refl ect the incongruencies in comparison to the 16S rDNA gene, generally used for taxonomic relationships. Such discrepancies in gene inheritance have been termed as horizontal gene transfer (HGT) events. In the post-genomic era, the explosion of known sequences through large-scale sequencing projects has unraveled the weakness of traditional 16S rDNA gene tree based evolutionary model. Various methods to scrutinize HGT events include atypical composition, abnormal sequence similarity, anomalous phylogenetic distribution, unusual phyletic patterns, etc. Since HGT generates greater genetic diversity, it is likely to increase resource use and ecosystem resilience.

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“…The recX gene that is situated 161 bp downstream of the H. influenzae recA gene (an organization that is observed in several bacterial species) was also investigated. In E. coli, recX is cotranscribed with recA (Pagès et al, 2003) and inhibits recombinase, co-protease and ATP hydrolysis activities of RecA (Venkatesh et al, 2002;Pagès et al, 2003;Stohl et al, 2003), indicating that recX may play an important role in SOS responses.…”

Section: Northern Blot and Rt-pcr Analysis Of The Sos Responsementioning

confidence: 99%

Induction of the SOS regulon of Haemophilus influenzae does not affect phase variation rates at tetranucleotide or dinucleotide repeats

2005

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Haemophilus influenzae has microsatellite repeat tracts in 59 coding regions or promoters of several genes that are important for commensal and virulence behaviour. Changes in repeat number lead to switches in expression of these genes, a process referred to as phase variation. Hence, the virulence behaviour of this organism may be influenced by factors that alter the frequency of mutations in these repeat tracts. In Escherichia coli, induction of the SOS response destabilizes dinucleotide repeat tracts. H. influenzae encodes a homologue of the E. coli SOS repressor, LexA. The H. influenzae genome sequence was screened for the presence of the minimal consensus LexA-binding sequence from E. coli, CTG(N) 10 CAG, in order to identify genes with the potential to be SOS regulated. Twenty-five genes were identified that had LexA-binding sequences within 200 bp of the start codon. An H. influenzae non-inducible LexA mutant (lexA NI ) was generated by site-directed mutagenesis. This mutant showed increased sensitivity, compared with wild-type (WT) cells, to both UV irradiation and mitomycin C (mitC) treatment. Semi-quantitative RT-PCR studies confirmed that H. influenzae mounts a LexA-regulated SOS response following DNA assault. Transcript levels of lexA, recA, recN, recX, ruvA and impA were increased in WT cells following DNA damage but not in lexA NI cells. Induction of the H. influenzae SOS response by UV irradiation or mitC treatment did not lead to any observable SOS-dependent changes in phase variation rates at either dinucleotide or tetranucleotide repeat tracts. Treatment with mitC caused a small increase in phase variation rates in both repeat tracts, independently of an SOS response. We suggest that the difference between H. influenzae and E. coli with regard to the effect of the SOS response on dinucleotide phase variation rates is due to the absence of any of the known trans-lesion synthesis DNA polymerases in H. influenzae.

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Escherichia coli RecX Inhibits RecA Recombinase and Coprotease Activities in Vitro and in Vivo

Cited by 170 publications

References 42 publications

SSB Antagonizes RecX-RecA Interaction

SSB Antagonizes RecX-RecA Interaction

Phylogeny vs genome reshuffling: horizontal gene transfer

Induction of the SOS regulon of Haemophilus influenzae does not affect phase variation rates at tetranucleotide or dinucleotide repeats

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