The SbcCD protein of Escherichia coli is related to two putative nucleases in the UvrA superfamily of nucleotide-binding proteins

Leach, David R. F.; Lloyd, Robert G.; Coulson, Andrew

doi:10.1007/bf00120998

Cited by 22 publications

(12 citation statements)

References 25 publications

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“…SbcC functions in complex with a coordinately regulated protein, SbcD, to mediate ATP-dependent exonuclease activity (12a, 40). It is interesting that the three known Mre11 homologs exhibit significant homology to the SbcD proteins from E. coli and Bacillus subtilis (23,39,43). Similarity between SbcC/SbcD and ScRad50/ScMre11 has been noted previously (72).…”

Section: Discussionmentioning

confidence: 61%

Human Rad50 Is Physically Associated with Human Mre11: Identification of a Conserved Multiprotein Complex Implicated in Recombinational DNA Repair

Dolganov¹,

Maser

Novikov³

et al. 1996

Molecular and Cellular Biology

197

127

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In this report, we describe the identification and molecular characterization of a human RAD50 homolog, hRAD50. hRAD50 was included in a collection of cDNAs which were isolated by a direct cDNA selection strategy focused on the chromosomal interval spanning 5q23 to 5q31. Alterations of the 5q23-q31 interval are frequently observed in myelodysplasia and myeloid leukemia. This strategy was thus undertaken to create a detailed genetic map of that region. Saccharomyces cerevisiae RAD50 (ScRAD50) is one of three yeast RAD52 epistasis group members (ScRAD50, ScMRE11, and ScXRS2) in which mutations eliminate meiotic recombination but confer a hyperrecombinational phenotype in mitotic cells. The yeast Rad50, Mre11, and Xrs2 proteins appear to act in a multiprotein complex, consistent with the observation that the corresponding mutants confer essentially identical phenotypes. In this report, we demonstrate that the human Rad50 and Mre11 proteins are stably associated in a protein complex which may include three other proteins. hRAD50 is expressed in all tissues examined, but mRNA levels are significantly higher in the testis. Other human RAD52 epistasis group homologs exhibit this expression pattern, suggesting the involvement of human RAD52 epistasis group proteins in meiotic recombination. Human RAD52 epistasis group proteins are highly conserved and act in protein complexes that are analogous to those of their yeast counterparts. These findings indicate that the function of the RAD52 epistasis group is conserved in human cells.Acute myeloid leukemia (AML) and myelodysplastic disease are associated with alterations of the 5q23-q31 chromosomal interval (25,60,63). Extensive analysis of patient material has narrowed the commonly deleted region to 5q31, leading to the proposal that an AML tumor suppressor is contained within this region. This interval has thus been designated the critical region (45,46,60). We undertook the creation of a detailed transcriptional and physical map of the 5q23-q31 interval and used direct cDNA selection to identify potential tumor suppressors in this region (16a). Among the cDNAs isolated by this method was hRAD50, a human homolog of the Saccharomyces cerevisiae DNA repair gene, ScRAD50. We have mapped the hRAD50 locus to 5q31, placing it in the critical region proposed to contain the AML tumor suppressor (45). Its homology to ScRAD50 argues that hRAD50 encodes a protein that is involved in human recombinational DNA repair. Double-strand-break (DSB) repair proteins are involved in diverse DNA recombination processes in mammalian and yeast cells. In addition to conferring sensitivity to DNA-damaging agents, DSB repair deficiency affects meiotic and mitotic recombination, mating-type switching, and the assembly of antigen receptor genes (20,86). Although defects in DSB repair and DNA recombination are coincident in both mammals and S. cerevisiae, the prevalent mechanisms of recombinational DNA repair differ significantly in these systems (8,26). Nonhomologous recombination is much more frequen...

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Section: Discussionmentioning

confidence: 61%

Human Rad50 Is Physically Associated with Human Mre11: Identification of a Conserved Multiprotein Complex Implicated in Recombinational DNA Repair

Dolganov¹,

Maser

Novikov³

et al. 1996

Molecular and Cellular Biology

197

127

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“…SbcA and sbcB are generally thought to activate exoVIII, a 5Ј-3Ј exonuclease, and to inactivate exoI, a 3Ј-5Ј exonuclease, respectively (50,51). SbcC and sbcD suppressors also are thought to encode nuclease activities, but their substrate specificities have not been defined (52). Thus, exonucleases involved in the recF pathway appear to process DNA ends so as to generate a 3Ј overhang.…”

Section: Discussionmentioning

confidence: 99%

recF and recR are required for the resumption of replication at DNA replication forks in Escherichia coli

Courcelle

Carswell-Crumpton

Hanawalt

1997

Proc. Natl. Acad. Sci. U.S.A.

205

281

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Escherichia coli containing a mutation in recF are hypersensitive to UV. However, they exhibit normal levels of conjugational or transductional recombination unless the major pathway (recBC) is defective. This implies that the UV sensitivity of recF mutants is not due to a defect in recombination such as occurs during conjugation or transduction. Here, we show that when replication is disrupted, at least two genes in the recF pathway, recF and recR, are required for the resumption of replication at DNA replication forks, and that in their absence, localized degradation occurs at the replication forks. Our observations support a model in which recF and recR are required to reassemble a replication holoenzyme at the site of a DNA replication fork. These results, when taken together with previous literature, suggest that the UV hypersensitivity of recF cells is due to an inability to resume replication at disrupted replication forks rather than to a defect in recombination. Current biochemical and genetic data on the conditions under which recF-mediated recombination occurs suggest that the recombinational intermediate also may mimic the structure of a disrupted replication fork.

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“…The derived amino acid sequences of SbcC and SbcD are similar to those of the putative major exonucleases of bacteriophage T4 (gp46 and gp47) and T5 (gpD13 and gpD12) (14,20). In addition, the gam gene of bacteriophage allows palindrome-containing phage to plate on strains of E. coli that are sbcCD ϩ , suggesting that the Gam protein might actually inhibit two nucleases, RecBCD and SbcCD (28).…”

mentioning

confidence: 99%

“…They are more closely related to SbcD than other members of the phosphoesterase family and, it has been suggested, are mechanistically similar (15,16). The sbcC gene encodes a large 118.7-kDa polypeptide that contains the ATP-A and ATP-B nucleotide binding motifs in globular regions at either end of the protein (14,20). These are separated by a large ␣-helical region that is predicted to form two coiled-coil domains interrupted by a short spacer (16).…”

mentioning

confidence: 99%

Overexpression, Purification, and Characterization of the SbcCD Protein from Escherichia coli

Connelly

Leau

Okely

et al. 1997

Journal of Biological Chemistry

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The sbcC and sbcD genes mediate palindrome inviability in Escherichia coli. The sbcCD operon has been cloned into the plasmid pTrc99A under the control of the strong trc promoter and introduced into a strain carrying a chromosomal deletion of sbcCD. The SbcC and SbcD polypeptides were overexpressed to 6% of total cell protein, and both polypeptides copurified in a four-step purification procedure. Purified SbcCD is a processive double-strand exonuclease that has an absolute requirement for Mn 2؉ and uses ATP as a preferred energy source. Gel filtration chromatography and sedimentation equilibrium analyses were used to show that the SbcC and SbcD polypeptides dissociate at some stage after purification and that this dissociation is reversed by the addition of Mn 2؉ . We demonstrate that SbcD has the potential to form a secondary structural motif found in a number of protein phosphatases and suggest that it is a metalloprotein that contains the catalytic center of the SbcCD exonuclease.

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The SbcCD protein of Escherichia coli is related to two putative nucleases in the UvrA superfamily of nucleotide-binding proteins

Cited by 22 publications

References 25 publications

Human Rad50 Is Physically Associated with Human Mre11: Identification of a Conserved Multiprotein Complex Implicated in Recombinational DNA Repair

Human Rad50 Is Physically Associated with Human Mre11: Identification of a Conserved Multiprotein Complex Implicated in Recombinational DNA Repair

recF and recR are required for the resumption of replication at DNA replication forks in Escherichia coli

Overexpression, Purification, and Characterization of the SbcCD Protein from Escherichia coli

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