一类新型大肠杆菌recBC突变体：RecBC酶在同源重组中的作用探讨
A new class of Escherichia coli recBC mutants: implications for the role of RecBC enzyme in homologous recombination.
作者信息
Chaudhury A M, Smith G R
出版信息
Proc Natl Acad Sci U S A. 1984 Dec;81(24):7850-4. doi: 10.1073/pnas.81.24.7850.
Mutants of Escherichia coli sensitive to phage T4 gene 2 mutants were obtained following ethyl methanesulfonate mutagenesis. By mapping and complementation analysis, the mutations in each of the six mutants are in recB and recC. By both in vivo and in vitro analyses, the nuclease activity of RecBC enzyme is undetectable in these mutants. However, by several other criteria, such as proficiency in recombination, relative resistance to UV radiation, and viability of the cells in the culture, these mutants are almost identical to their recBC+ parent. The properties of these mutants indicate that the ATP-dependent double-stranded DNA exonuclease activity of RecBC enzyme is not required for recombination. Chi recombinational hotspots, which stimulate recombination by the RecBC pathway, have no detectable activity in the mutants. This result suggests that the nuclease activity of RecBC enzyme is required for Chi activity and is consistent with the hypothesis that Chi stimulates recombination by directing RecBC enzyme to cut DNA at or near Chi.
通过甲磺酸乙酯诱变获得了对噬菌体T4基因2突变体敏感的大肠杆菌突变体。通过定位和互补分析，六个突变体中每个突变体的突变都位于recB和recC基因。通过体内和体外分析，在这些突变体中均未检测到RecBC酶的核酸酶活性。然而，根据其他几个标准，如重组能力、对紫外线辐射的相对抗性以及培养物中细胞的活力，这些突变体与其recBC+亲本几乎相同。这些突变体的特性表明，RecBC酶的ATP依赖性双链DNA外切核酸酶活性对于重组不是必需的。通过RecBC途径刺激重组的Chi重组热点在突变体中没有可检测到的活性。这一结果表明，RecBC酶的核酸酶活性是Chi活性所必需的，并且与Chi通过引导RecBC酶在Chi处或其附近切割DNA来刺激重组的假设一致。
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