INTERACTION OF RECBCD ENZYME WITH DNA DAMAGED BY GAMMA-RADIATION
INTERACTION OF RECBCD ENZYME WITH DNA DAMAGED BY GAMMA-RADIATION
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DOI：
10.1007/bf00282458
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发表时间：
1991-08-01
期刊：
影响因子：
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通讯作者：
TRGOVCEVIC, Z
中科院分区：
文献类型：
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作者：
BRCICKOSTIC, K;SALAJSMIC, E;TRGOVCEVIC, Z
噬菌体T4的基因2突变体(T4 2-)的DNA被细菌细胞质中的RecBCD酶降解。因此，在正常条件下，recBCD+ 细胞无法支持噬菌体 T4 2- 的生长。仅当细胞质中不存在 RecBCD 酶的溶核活性时，T4 2- 感染的细菌才能够形成噬菌斑。我们发现，如果在感染 T4 2- 之前，recBCD+ 细胞已暴露于伽马辐射，则它们可以形成斑块。这表明伽马射线诱导的细菌 DNA 损伤（例如双链断裂）与 RecBCD 酶结合。这种结合使酶能够开始降解细菌染色体，但同时阻止其对次要 DNA 物种（例如未受保护的感染噬菌体染色体）末端的降解作用。染色体 DNA 的降解发生在辐射后早期，在伽马射线照射后约 60 分钟停止。 RecBCD 酶对 T4 2-DNA 的溶核作用重新出现，同时细菌 DNA 降解停止。 RecBCD 酶对 T4 2-DNA 的溶核作用的停止和重新出现都依赖于功能性的recA 基因产物。这些结果表明，辐照后 DNA 降解是通过从受损染色体上依赖 recA 去除 RecBCD 酶来控制的。通过利用温度敏感突变体recB270，我们发现RecBCD介导的伽马射线诱导损伤修复发生在辐射后早期，即辐射后DNA降解期间。结果表明，RecBCD 酶的 RecD 亚基也参与了这种修复。
The DNA of a gene 2 mutant (T4 2-) of phage T4 is degraded by RecBCD enzyme in the bacterial cytoplasm. Under normal conditions, recBCD+ cells are therefore incapable of supporting the growth of phage T4 2-. Only if the nucleolytic activity of RecBCD enzyme is absent from the cytoplasm are T4 2- -infected bacteria able to form plaques. We found that recBCD+ cells can form plaques if, before infection with T4 2-, they have been exposed to gamma radiation. It is suggested that gamma ray-induced lesions of the bacterial DNA (e.g., double-strand breaks) bind RecBCD enzyme. This binding enables the enzyme to begin to degrade the bacterial chromosome, but simultaneously prevents its degradative action on the ends of minor DNA species, such as unprotected infecting phage chromosomes. Degradation of the chromosomal DNA, which occurs during the early postirradiation period, ceases about 60 min after gamma ray exposure. The reappearance of the nucleolytic action of RecBCD enzyme on T4 2- DNA accompanies the cessation of degradation of bacterial DNA. Both, this cessation and the reappearance of the nucleolytic action of RecBCD enzyme on T4 2- DNA depend on a functional recA gene product. These results suggest that postirradiation DNA degradation is controlled by the recA-dependent removal of RecBCD enzyme from the damaged chromosome. By making use of the temperature-sensitive mutant recB270, we showed that RecBCD-mediated repair of gamma ray-induced lesions occurs during the early postirradiation period, i.e. during postirradiation DNA degradation. It is shown that the RecD subunit of RecBCD enzyme also participates in this repair.