Mutants of Escherichia coli K-12 defective in DNA repair and in genetic recombination.
Mutants of Escherichia coli K-12 defective in DNA repair and in genetic recombination.
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发表时间：
1966-06
期刊：
影响因子：
3.3
通讯作者：
P. Howard-Flanders;L. Theriot
中科院分区：
文献类型：
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作者：
P. Howard-Flanders;L. Theriot
暴露于紫外线（UV）下，Bclaria很容易被杀死，这可能是细菌DNA中形成UV光产物的结果。还已知嘧啶二聚体是以高产率形成的光产物之一，并且细菌通常含有用于修复含有这些产物的DNA的有效机制。嘧啶二聚体在孵育过程中从DNA中切除，并且可以回收，仍然包含在短寡核苷酸中。这种切除似乎涉及单链DNA的中断，随后是局部DNA断裂和修复合成（SETLOW and CARRIER 1964;博伊斯and HOWARD-FLANDERS 1964; PETTIJOHN and HANAWALT 1964）。这些观察结果之所以有趣，不仅是因为它们揭示了损伤DNA修复的有效且可能广泛的过程机制，还因为它们表明局部修复可以发生在双螺旋的一条链中。这种DNA修复机制可能与遗传交换机制有关。通过发现噬菌体重组体可以通过连接预先存在的噬菌体DNA分子的片段而形成，获得了对遗传重组机制的深入了解（MESELSON和WEIGLE 1961）。由于必须保持噬菌体基因组碱基序列的连续性，因此可能需要来自每个亲本分子的重叠单链之间的碱基配对作为重组体形成的前奏（LEVINTHAL 1959）。有人认为，重组过程可能是通过重叠两侧的局部DNA修复合成完成的（MESELSON 1964），某些酶可能参与遗传重组和辐射后的修复（HOWARD-FLANDERS and博伊斯1964）。通过分离E. coZi K-12，当与合适的供体菌株交配时失去了形成重组体的能力。由于这些突变体能够接受遗传物质normafly，似乎它们可能在将供体DNA整合到受体染色体中的过程中有缺陷（表型符号Kec-）。由于修复和重组之间的关系，测试了菌株暴露于紫外线的存活能力，发现其具有高度辐射敏感性（WARNIK和MARGULIES 1965）。暴露于紫外线后，这些突变体过度降解其DNA，并且不能掺入标记的胸苷（BAUK，CHAMBERLIN，博伊斯和HOWARD-FLANDERS 1966）。
BACTERIA are readily killed by exposure to ultraviolet light (UV) , presumably as the result of the formation of UV photoproducts in the bacterial DNA. It is also known that pyrimidine dimers are among the photoproducts formed with a high yield, and that bacteria normally contain an efficient mechanism for the repair of DNA containing these products. Pyrimidine dimers are excised from DNA during incubation and can be recovered, still contained within a short oligonucleotide. This excision appears to involve the interruption of single DNA strands, and to be followed by local DNA breakdown and repair synthesis (SETLOW and CARRIER 1964; BOYCE and HOWARD-FLANDERS 1964; PETTIJOHN and HANAWALT 1964). These observations are of interest not only because they reveal the mechanism of an effective and possibly widespread process for the repair of injured DNA, but also because they suggest that local repair can occur in one strand of a double helix. This mechanism for DNA repair may be related to the mechanism of genetic exchange. An insight into the mechanisms of genetic recombination was gained through the discovery that h bacteriophage recombinants can be formed by joining fragments of preexisting phage DNA molecules (MESELSON and WEIGLE 1961). As continuity in the base sequence of the phage genome must be preserved, base pairing between overlapping single strands from each parentel molecule is presumably required as a prelude to the formation of a recombinant ( LEVINTHAL 1959). It has been suggested that the process of recombination may be completed by local DNA repair synthesis on either side of the overlap (MESELSON 1964) and that certain of the enzymes involved may serve in both genetic recombination and in repair after irradiation ( HOWARD-FLANDERS and BOYCE 1964). Further evidence in support of these concepts has been obtained through the isolation of mutants of E. coZi K-12 that have lost the ability to form recombinants when mated with suitable donor strains. As these mutants are able to accept genetic material normafly, it appears that they may be defective in the process of integrating the donor DNA into the recipient chromosome (phenotype symbol Kec-) . Because of the suggested relationship between repair and recombination, the strains were tested for ability to survive exposure to UV, and were found to be highly radiosensitive (CLARK and MARGULIES 1965). After exposure to UV, these mutants degrade their DNA excessively and fail to incorporate labeled thymidine ( CLARK, CHAMBERLIN, BOYCE, and HOWARD-FLANDERS 1966).