Repair by genetic recombination in bacteria: overview

Conference · Wed Jan 01 04:00:00 EST 1975

OSTI ID:4144770

Howard-Flanders, P; Hanawalt, P C ^[1]

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1. ed.

DNA molecules that have been damaged in both strands at the same level are not subject to repair by excision but instead can be repaired through recombination with homologous molecules. Examples of two-strand damage include postreplication gaps opposite pyrimidine dimers, two-strand breaks produced by x- rays, and chemically induced interstrand cross-links. In ultraviolet-irradiated bacteria, and newly synthesized DNA is of length equal to the interdimer spacing. With continued incubation, this low-molecular-weight DNA is joined into high- molecular-weight chains (postreplication repair), a process associated with sister exchanges in bacteria. Recombination is initiated by pyrimidine dimers opposite postreplication gaps and by interstrand cross-links that have been cut by excision enzymes. The free ends at the resulting gaps presumably initiate the exchanges. Postreplication repair in Escherichia coli occurs in recB$sup -$ and recC$sup -$ but is greatly slowed in recF$sup -$ mutants. RecB and recC are the structural genes for exonuclease V, which digests two-stranded DNA by releasing oligonucleotides first from one strand and then from the other. The postreplication sister exchanges in ultraviolet-irradiated bacteria result in the distribution of pyrimidine dimers between parental and daughter strands, indicating that long exchanges involving both strands of each duplex occur. The R1 restriction endonuclease from E. coli has been used to cut the DNA of a bacterial drug-resistance transfer factor with one nuclease-sensitive site, and also DNA from the frog Xenopus enriched for ribosomal 18S and 28S genes. The fragments were annealed with the cut plasmid DNA and ligated, producing a new larger plasmid carrying the eukaryotic rDNA and able to infect and replicate in E. coli. (auth)

• Research Organization: Yale Univ. School of Medicine, New Haven
• NSA Number: NSA-33-012274
• OSTI ID: 4144770
• Country of Publication: United States
• Language: English

Related Subjects

*DNA-- BIOLOGICAL REPAIR
*ESCHERICHIA COLI-- GENE RECOMBINATION
*GENE RECOMBINATION
560131* --Biomedical Sciences
Applied Studies--Radiation Effects--Radiation Effects on Microorganisms--Basic Studies
BIOSYNTHESIS
DIMERS
ENZYMES
FROGS
GENES
MOLECULES
N48310* --Life Sciences--Radiation Effects on Microorganisms- -Basic Studies
NUCLEASES
PYRIMIDINES
STRAND BREAKS
ULTRAVIOLET RADIATION
X RADIATION