Molecular organization of<i>sbcC</i>, a gene that affects genetic recombination and the viability of DNA palindromes in<i>Escherichia coli</i>K-12

Naom, Isam; Morton, Stuart J.; Leach, David R. F.; Lloyd, Robert G.

doi:10.1093/nar/17.20.8033

Cited by 38 publications

(47 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The sbcC gene was mapped, cloned and sequenced (Naom et al 1989). This revealed that sbcC was co-transcribed with another gene originally denoted ORF45.…”

Section: Introductionmentioning

confidence: 99%

The sbcC and sbcD genes of Escherichia coli encode a nuclease involved in palindrome inviability and genetic recombination

1996

View full text Add to dashboard Cite

Background: Long DNA palindromes have the potential to adopt hairpin or cruciform secondary structures that inhibit DNA replication. In Escherichia coli, this palindrome-mediated inviability results from the activity of the sbcC and sbcD genes, and genetic observations have suggested that they may encode a nuclease. Mutations in these genes also restore the defect in genetic recombination associated with recBC sbcB mutants.

show abstract

“…The sbcC gene was mapped, cloned and sequenced (Naom et al 1989). This revealed that sbcC was co-transcribed with another gene originally denoted ORF45.…”

Section: Introductionmentioning

confidence: 99%

The sbcC and sbcD genes of Escherichia coli encode a nuclease involved in palindrome inviability and genetic recombination

1996

View full text Add to dashboard Cite

show abstract

“…The sbcC region of the chromosome has been cloned and sequenced, and the gene product has been identified as a protein of 118 kDa (23). The DNA encoding sbcC lies downstream of an open reading frame (orf-45) encoding a polypeptide of 45 kDa, with the TGA stop codon for orf-45 overlapping the proposed ATG start codon for sbcC.…”

mentioning

confidence: 99%

Identification of sbcD mutations as cosuppressors of recBC that allow propagation of DNA palindromes in Escherichia coli K-12

1992

View full text Add to dashboard Cite

The function of an open reading frame (orf-45) located upstream of the sbcC gene of Escherichia coli was investigated. Mutations that inactivate sbcC improve the ability to propagate Ared gam phage that carry a palindromic sequence in their DNA. They also act with sbcB mutations as cosuppressors of the defects in recombination, DNA repair, and cell viability associated with recBC mutations. A 1,282-bp cassette encoding resistance to kanamycin was used to disrupt orf-45. The mutation, which has a polar effect on the expression of sbcC, allowed stable propagation of palindromic k phage even when the sbcC gene product was provided in trans. Additional nonpolar mutations in orf-45 were isolated on the basis of their ability to improve the growth of recBC sbcB strains. These mutations also confer resistance to mitomycin C, allow efficient recombination in Hfr crosses, and facilitate stable propagation of palindromic phage. It is concluded that the products of orf-45 and sbcC are functionally related. The orf-45 gene is therefore renamed sbcD.The sbcC gene of Escherichia coli was defined originally by mutations that arise spontaneously in recBC sbcB strains (16). These mutations act with mutations in sbcB to suppress the defects in recombination and DNA repair associated with the recBC genotype and are selected, therefore, during normal growth because of the improved viability. Subsequently, sbcC single mutants were shown to be good hosts for a Xred gam phage carrying a DNA sequence with palindromic symmetry (Xpal) (5). Phage of this type grow poorly in sbcC+ cells. Leach and Stahl (13) had observed this feature of the sbcC phenotype in their earlier work with recBC sbcB sbcC strains but, because isogenic strains were not constructed and used for comparisons, had attributed it to the absence of exonuclease V (RecBCD enzyme) and exonuclease I (the product of sbcB). This seemed reasonable since palindromes might form hairpins or cruciforms which could be recognized and cleaved by nucleases that normally resolve Holliday intermediates in genetic recombination. Kulkarni and Stahl (11) MATERIALS AND METHODSBacterial strains and X phages. The E. coli K-12 strains and A phages used are described in Table 1. Phage stocks were prepared on strain JC7623, which allows stable propagation of the 571-bp palindrome carried by XMMS1632.Plasmids. Plasmid constructs carrying DNA inserts from the sbcC-orf-45 region of the chromosome are shown in Fig. 1. pSB43, pJP77, and pIN510 are described in detail elsewhere (3,23,28). pIN507 corresponds to pJP77 sbcC:: TnlOOO no. 5 described by Naom et al. (23). pFG103 was made by cloning a BamHI-HindIII fragment of approximately 14.5 kb from pJP77 into pACYC184 (6). A 1,282-bp cassette (kan) encoding resistance to kanamycin was cloned from pUC4K (29) into the unique PstI site of pFG103 to give pFG103K. pFG106 was constructed by removing the Kmr insertion from pFG103K by digestion with EcoRI and inserting it into the EcoRI site of the temperature-sensitive replicon pHSG415 (10). The sbcC+ construc...

show abstract

“…From the data presented, it is clear that transfer of sbcC+ has a substantial effect on the types of recombinants recovered in Hfr crosses with recBC sbcBC strains. The reduced linkage of unselected proximal markers and the higher incidence of multiple exchanges raise the possibility that expression of the dominant sbcC+ allele (18,30) a The analysis was as described in the footnotes to Table 2 except that the ara marker was not scored and the locations of genetic markers and crossover intervals are as shown in Fig. 2.…”

Section: Methodsmentioning

confidence: 99%

“…The sbcB mutation inactivates exonuclease I, the product of sbcB (15,16), which digests single-stranded DNA in the 3'-to-5' direction (17). sbcC encodes a 118-kDa polypeptide of unknown activity (30), although there is indirect evidence that it may be a nuclease that attacks palindromic DNA (5,13,14,30).…”

mentioning

confidence: 99%

“…Lloyd and Buckman (18) showed that recBC sbcB (sbcC+) strains grow very slowly, have a lower cell viability than recBC mutants, and are somewhat deficient in recombination. Since sbcC+ is dominant (18,30), Hfr transfer of this allele to recBC sbcBC recipients is likely therefore to have a profound effect on the outcome of the cross. The results presented here show that this is indeed the case and that the conclusions drawn from earlier studies need to be re-examined.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Linkage distortion following conjugational transfer of sbcC+ to recBC sbcBC strains of Escherichia coli

Lloyd

1991

J Bacteriol

View full text Add to dashboard Cite

Conjugational recombination in Escherichia coli depends normally on RecBCD enzyme, a multifunctional nuclease and D)NA helicase produced by the recB, recC, and recD genes. However, recombination can proceed efficiently without RecBCD in recB or recC strains carrying additional mutations in both the sbcB and sbcC genes. Recombination in these strains, sometimes referred to as the RecF pathway, requires gene products that are not essential in the RecBCD-dependent process predominating in the wild type. It has also been reported to produce a different spectrum of recombinant genotypes in crosses with Hfr donors. However, the sbcC+ gene was unknowingly transferred to the recipient strain in some of these crosses, and this may have affected the outcome. This possibility was examined by conducting parallel crosses with Hfr donors that were either wild type or mutant for sbcC. Transfer of sbcC+ from an Hfr donor is shown to alter the frequency of recombinant genotypes recovered. There is a severe reduction in progeny that inherit donor markers linked to the sbcC+ allele and an increase in the incidence of multiple exchanges. Colonies of mixed genotype for one or more of the unselected proximal markers are also much more prevalent. Since the yield of recombinants is lower than normal, these changes are attributed to the reduced viability of recombinants that inherit sbcC+ from the Hfr donor. When the Hfr donor used is also mutant for sbcC, the yield of recombinants is greater and the frequencies of the different genotypes recovered are similar to those obtained in crosses with a rec+ sbc+ recipient, in which transfer of sbcC' has no apparent effect. Earlier studies are re-examined in light of these findings. It is concluded that, while recombination in recBC sbcBC strains involves different enzymes, the underlying molecular mechanism is essentially the same as that in the wild type.

show abstract

Molecular organization ofsbcC, a gene that affects genetic recombination and the viability of DNA palindromes inEscherichia coliK-12

Cited by 38 publications

References 40 publications

The sbcC and sbcD genes of Escherichia coli encode a nuclease involved in palindrome inviability and genetic recombination

The sbcC and sbcD genes of Escherichia coli encode a nuclease involved in palindrome inviability and genetic recombination

Identification of sbcD mutations as cosuppressors of recBC that allow propagation of DNA palindromes in Escherichia coli K-12

Linkage distortion following conjugational transfer of sbcC+ to recBC sbcBC strains of Escherichia coli

Contact Info

Product

Resources

About