Minton K W, Daly M J
Department of Pathology, F. E. Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814-4799, USA.
Bioessays. 1995 May;17(5):457-64. doi: 10.1002/bies.950170514.
The bacterium Deinococcus (formerly Micrococcus) radiodurans and other members of the eubacterial family Deinococaceae are extremely resistant to ionizing radiation and many other agents that damage DNA. Stationary phase D. radiodurans exposed to 1.0-1.5 Mrad gamma-irradiation sustains > 120 DNA double-strand breaks (dsbs) per chromosome; these dsbs are mended over a period of hours with 100% survival and virtually no mutagenesis. This contrasts with nearly all other organisms in which just a few ionizing radiation induced-dsbs per chromosome are lethal. In this article we present an hypothesis that resistance of D. radiodurans to ionizing radiation and its ability to mend radiation-induced dsbs are due to a special form of redundancy wherein chromosomes exist in pairs, linked to each other by thousands of four-stranded (Holliday) junctions. Thus, a dsb is not a lethal event because the identical undamaged duplex is nearby, providing an accurate repair template. As addressed in this article, much of what is known about D. radiodurans suggests that it is particularly suited for this proposed novel form of DNA repair.
耐辐射球菌（以前称为微球菌）及真细菌科耐辐射球菌科的其他成员对电离辐射和许多其他能损伤DNA的因子具有极强的抗性。处于稳定期的耐辐射球菌暴露于1.0 - 1.5兆拉德的γ辐射下，每条染色体可承受超过120个DNA双链断裂（dsbs）；这些双链断裂在数小时内得以修复，存活率达100%，且几乎没有诱变现象。这与几乎所有其他生物形成对比，在其他生物中，每条染色体仅少数几个电离辐射诱导的双链断裂就可致死。在本文中，我们提出一个假说，即耐辐射球菌对电离辐射的抗性及其修复辐射诱导双链断裂的能力源于一种特殊形式的冗余，其中染色体成对存在，通过数千个四链（霍利迪）连接相互连接。因此，双链断裂并非致死事件，因为相同的未受损双链就在附近，可提供精确的修复模板。如本文所述，关于耐辐射球菌的许多已知信息表明，它特别适合这种提出的新型DNA修复形式。
