Heteroduplex joint formation in Escherichia coli recombination is initiated by pairing of a 3′-ending strand

被引:24
作者
Friedman-Ohana, R [1 ]
Cohen, A [1 ]
机构
[1] Hebrew Univ Jerusalem, Hadassah Med Sch, Dept Mol Biol, IL-91010 Jerusalem, Israel
关键词
genetic recombination; RecBCD; RecD; strand exchange; RecJ;
D O I
10.1073/pnas.95.12.6909
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
The formation of heteroduplex joints in Escherichia coli recombination is initiated by invasion of double-stranded DNA by a single-stranded homologue, To determine the polarity of the invasive strand, linear molecules with direct terminal repeats were released by in vivo restriction of infecting chimeric phage DNA and heteroduplex products of intramolecular recombination were analyzed, With this substrate, the invasive strand is expected to be incorporated into the circular crossover product and the complementary strand is expected to be incorporated into the reciprocal linear product. Strands of both polarities were incorporated into heteroduplex structures, but only strands ending 3' at the break were incorporated into circular products, This result indicates that invasion of the 3'-ending strand initiates the heteroduplex joint formation and that the complementary 5'-ending strand is incorporated into heteroduplex structures in the process of reciprocal strand exchange. The polarity of the invasive strand was not affected by recD, recJ, or xonA mutations. However, xon4 and recJ mutations increased the proportion of heteroduplexes containing 5'-ending strands. This observation suggests that RecJ exonuclease and exonuclease I mag enhance recombination by degrading the displaced strands during branch migration and thereby causing strand exchange to be unidirectional.
引用
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页码:6909 / 6914
页数:6
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