Ikeda H, Shimizu H, Ukita T, Kumagai M
Department of Molecular Biology, University of Tokyo, Japan.
Adv Biophys. 1995;31:197-208. doi: 10.1016/0065-227x(95)99392-3.
We developed a novel assay system for illegitimate recombination, in which the frequency of the formation of lambda Spi- phages formed during prophage induction was measured with an E. coli P2 lysogen as the indicator bacteria. Since almost all of the lambda Spi- phages thus detected contain attR, they have essentially the same structures as lambda bio transducing phages, indicating that this assay system enables us to detect specialized transducing phages that produce heterogenote transductants, thus ignoring the occurrences of docL and docR particles which carry only one cohesive end. The following results on the formation of specialized transducing phages have been obtained by this assay system to date. (1) Irradiation with UV light greatly enhanced the formation of lambda Spi- phages. (2) Treatments with other DNA-damaging agents also enhanced the formation of lambda Spi- phages. (3) Illegitimate recombination during prophage induction does not require the RecA function, indicating that enhancement of lambda Spi- phage formation is not controlled by the SOS regulatory system. (4) Preliminary results suggested that DNA gyrase is involved in the formation of lambda Spi- phage during pro-phage induction. Since the above results were consistent with most of the previous observations on the illegitimate recombination in other systems, the Spi- assay system can provide important clues to the mechanism of illegitimate recombination.
我们开发了一种用于检测异常重组的新型检测系统，该系统以大肠杆菌P2溶原菌作为指示菌，测定原噬菌体诱导过程中形成的λ Spi-噬菌体的形成频率。由于由此检测到的几乎所有λ Spi-噬菌体都含有attR，它们与λ bio转导噬菌体具有基本相同的结构，这表明该检测系统使我们能够检测产生异源基因型转导子的特异性转导噬菌体，从而忽略仅携带一个粘性末端的docL和docR颗粒的出现。迄今为止，通过该检测系统已获得以下关于特异性转导噬菌体形成的结果。（1）紫外线照射大大增强了λ Spi-噬菌体的形成。（2）用其他DNA损伤剂处理也增强了λ Spi-噬菌体的形成。（3）原噬菌体诱导过程中的异常重组不需要RecA功能，这表明λ Spi-噬菌体形成的增强不受SOS调节系统的控制。（4）初步结果表明，DNA促旋酶参与原噬菌体诱导过程中λ Spi-噬菌体的形成。由于上述结果与之前在其他系统中关于异常重组的大多数观察结果一致，因此Spi-检测系统可以为异常重组的机制提供重要线索。
