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χ*, a χ‐related 11‐mer sequence partially active in an E. coli recC * strain
Author(s) -
Handa Naofumi,
Ohashi Seishi,
Kusano Kohji,
Kobayashi Ichizo
Publication year - 1997
Publication title -
genes to cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.912
H-Index - 115
eISSN - 1365-2443
pISSN - 1356-9597
DOI - 10.1046/j.1365-2443.1997.1410339.x
Subject(s) - recbcd , biology , exonuclease , escherichia coli , mutant , microbiology and biotechnology , exonuclease iii , nucleic acid sequence , genetics , dna , polymerase , gene
Background: χ sequence (5′GCTGGTGG) of Escherichia coli was first identified as a site that increased the plaque size of bacteriophage λ. Subsequent studies showed that this site is responsible for both the attenuation of RecBCD exonuclease activity and the promotion of RecA, RecBCD‐mediated recombination. It is known that bacteriophage λ containing the χ site makes very small plaques on a recC * ( recC1004 ) mutant because χ is not recognized by the RecBC*D mutant enzyme. Results: We cloned E. coli chromosomal fragments in λ which allowed λ to form larger plaques on this recC * mutant. The fragments were found to share a χ‐like 11‐mer sequence, 5′GCTGGTG CTCG . Substitution of these fragments with a synthetic 11‐mer of this sequence and single‐base‐pair substitution analysis of its last four nucleotides demonstrated that this sequence is both necessary and sufficient for the observed activity. The sequence, designated χ* (chi‐star), protected rolling‐circle DNA replication in the recC * mutant and in the recBCD + strain, most likely because it attenuated the exonuclease activity of the RecBC*D and RecBCD + enzyme. χ*, did not significantly stimulate λ recombination in two assays. Conclusion: We have discovered that a mutant RecBCD enzyme responds, in vivo , to a longer χ variant.