Escherichia coli RecG and RecA proteins in R-loop formation.

Hong, Xiankang; Cadwell, Gregory W.; Kogoma, Tokio

doi:10.1002/j.1460-2075.1995.tb07233.x

Cited by 102 publications

(123 citation statements)

References 54 publications

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“…This activity appears to be important for ensuring efficient recombination in the presence of the PriA helicase (19). Furthermore, RecG can unwind R-loops, which helps to limit their accumulation in vivo (15,21,22). Clearly, these activities do not require RecG's interaction with a Holliday junction and therefore may not be as sensitive to the concentration of free Mg 2ϩ .…”

Section: Discussionmentioning

confidence: 99%

Targeting Holliday Junctions by the RecG Branch Migration Protein of Escherichia coli

Whitby¹,

Lloyd²

1998

Journal of Biological Chemistry

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The RecG protein of Escherichia coli is a junctionspecific DNA helicase that drives branch migration of Holliday intermediates in genetic recombination and DNA repair. The reaction was investigated using synthetic X-junctions. RecG dissociates X-junctions to flayed duplex products, although DNA unwinding of the heterologous arms is limited to <30 base pairs. Junction unwinding requires Mg 2؉ and the hydrolysis of ATP. X-junction DNA stimulates the ATPase activity of RecG. ATPase activity is also stimulated by linear duplex DNA, although to a lesser extent than by X-DNA, but not by linear single-stranded DNA. In situ 1,10-phenanthrolinecopper footprinting shows that RecG binds to the strand cross-over point at the center of the X-junction. Substrate recognition by RecG was investigated using DNAs that represented the various component parts of an Xjunction. The minimal DNA structure that RecG forms a stable complex with is a flayed duplex, suggesting that this is the critical feature for junction recognition by RecG. Junction binding and unwinding also depend critically on the concentration of free Mg 2؉ , excess free cation dramatically inhibiting both processes. These inhibitory effects are not mediated specifically by Mg 2؉ ; e.g. both Ca 2؉ and hexamminecobalt(III) chloride also inhibit X-junction binding and unwinding by RecG. The relative abilities of these cations to inhibit RecG-junction binding is correlated with their respective abilities to stack X-junction DNA. From this we conclude that RecG is unable to bind or binds very poorly to fully stacked X-junctions.

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Section: Discussionmentioning

confidence: 99%

Targeting Holliday Junctions by the RecG Branch Migration Protein of Escherichia coli

Whitby¹,

Lloyd²

1998

Journal of Biological Chemistry

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“…RecG-mediated R-loop removal renders the recG gene essential for the viability of RNase H mutants (rnh), and recG inactivation triggers the use of R-loops as alternative replication initiation points, a phenomenon termed constitutive stable DNA replication (38).…”

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confidence: 99%

Situational Repair of Replication Forks

Robu

Inman

Cox

2004

Journal of Biological Chemistry

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Replication forks often stall or collapse when they encounter a DNA lesion. Fork regression is part of several major paths to the repair of stalled forks, allowing nonmutagenic bypass of the lesion. We have shown previously that Escherichia coli RecA protein can promote extensive regression of a forked DNA substrate that mimics a possible structure of a replication fork stalled at a leading strand lesion. Using electron microscopy and gel electrophoresis, we demonstrate that another protein, E. coli RecG helicase, promotes extensive fork regression in the same system. The RecG-catalyzed fork regression is very efficient and faster than the

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“…RecG is required to limit the activity of PriA: Drawing the conclusion from the data in Figure 2 that RecG is needed to support junction resolution by RusA has to be tempered by evidence that RecG itself is required to maintain viability in the case of polA and dam cells (Hong et al 1995;Marinus 2000). Synthetic lethality assays based on a recG 1 derivative of pRC7 confirmed this was so for polA recG cells ( Figure 3A, panels i and ii).…”

Section: Resultsmentioning

confidence: 90%

“…These include the D loops and R loops that PriA protein could otherwise exploit to initiate stable DNA replication (SDR), a form of chromosome replication that is independent of oriC and of the initiator protein DnaA, and which also includes the replication primed by recombination during repair of chromosome breaks (Vincent et al 1996;Fukuoh et al 1997;Kogoma 1997;McGlynn et al 1997). SDR is elevated constitutively in cells lacking RecG (Hong et al 1995) and triggers severe overreplication of the chromosome when increased even further by damage to DNA. This sets in motion a pathological cascade that interferes with the cell cycle and which results in the formation of extraordinarily long filaments that bud off a small cell capable of normal growth and division only after a very long delay (Rudolph et al 2009a,b).…”

Section: T He Early Stages Of Genetic Recombination Inmentioning

confidence: 99%

“…With no means to distinguish parental strands from nascent strands, the MutHLS proteins initiate mismatch repair indiscriminately in dam mutants, which may result in chromosome breakage when repair tracks overlap ( Figure 1B). Thus, the viability of both polA and dam mutants depends on recombination proteins to repair DNA breaksRecBCD and RecA to initiate exchanges at the broken DNA ends and RuvABC to cleave Holliday junctions (Figure 1, A and B) (Lloyd et al 1974;Hong et al 1995;Kuzminov 1995;Ishioka et al 1998;Marinus 2000).…”

Section: T He Early Stages Of Genetic Recombination Inmentioning

confidence: 99%

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Promoting and Avoiding Recombination: Contrasting Activities of the Escherichia coli RuvABC Holliday Junction Resolvase and RecG DNA Translocase

et al. 2010

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RuvABC and RecG are thought to provide alternative pathways for the late stages of recombination in Escherichia coli. Inactivation of both blocks the recovery of recombinants in genetic crosses. RuvABC resolves Holliday junctions, with RuvAB driving branch migration and RuvC catalyzing junction cleavage. RecG also drives branch migration, but no nuclease has been identified that might act with RecG to cleave junctions, apart from RusA, which is not normally expressed. We searched for an alternative nuclease using a synthetic lethality assay to screen for mutations causing inviability in the absence of RuvC, on the premise that a strain without any ability to cut junctions might be inviable. All the mutations identified mapped to polA, dam, or uvrD. None of these genes encodes a nuclease that cleaves Holliday junctions. Probing the reason for the inviability using the RusA Holliday junction resolvase provided strong evidence in each case that the RecG pathway is very ineffective at removing junctions and indicated that a nuclease component most probably does not exist. It also revealed new suppressors of recG, which were located to the ssb gene. Taken together with the results from the synthetic lethality assays, the properties of the mutant SSB proteins provide evidence that, rather than promoting recombination, a major function of RecG is to curb potentially pathological replication initiated via PriA protein at sites remote from oriC.

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Escherichia coli RecG and RecA proteins in R-loop formation.

Cited by 102 publications

References 54 publications

Targeting Holliday Junctions by the RecG Branch Migration Protein of Escherichia coli

Targeting Holliday Junctions by the RecG Branch Migration Protein of Escherichia coli

Situational Repair of Replication Forks

Promoting and Avoiding Recombination: Contrasting Activities of the Escherichia coli RuvABC Holliday Junction Resolvase and RecG DNA Translocase

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