Bouthier de la Tour Claire, Toueille Magali, Jolivet Edmond, Nguyen Hong-Ha, Servant Pascale, Vannier Françoise, Sommer Suzanne
Univ Paris-Sud, CNRS UMR8621, CEA LRC42V, Institut de Génétique et Microbiologie, Bâtiment 409, 91405, Orsay Cedex, France.
Extremophiles. 2009 Sep;13(5):827-37. doi: 10.1007/s00792-009-0270-2. Epub 2009 Jul 22.
Deinococcus radiodurans contains a highly condensed nucleoid that remains to be unaltered following the exposure to high doses of gamma-irradiation. Proteins belonging to the structural maintenance of chromosome protein (SMC) family are present in all organisms and were shown to be involved in chromosome condensation, pairing, and/or segregation. Here, we have inactivated the smc gene in the radioresistant bacterium D. radiodurans, and, unexpectedly, found that smc null mutants showed no discernible phenotype except an increased sensitivity to gyrase inhibitors suggesting a role of SMC in DNA folding. A defect in the SMC-like SbcC protein exacerbated the sensitivity to gyrase inhibitors of cells devoid of SMC. We also showed that the D. radiodurans SMC protein forms discrete foci at the periphery of the nucleoid suggesting that SMC could locally condense DNA. The phenotype of smc null mutant leads us to speculate that other, not yet identified, proteins drive the compact organization of the D. radiodurans nucleoid.
耐辐射球菌含有高度浓缩的类核，在暴露于高剂量伽马射线照射后仍保持不变。属于染色体结构维持蛋白（SMC）家族的蛋白质存在于所有生物体中，并已证明其参与染色体浓缩、配对和/或分离。在此，我们使耐辐射细菌耐辐射球菌中的smc基因失活，出乎意料的是，发现smc基因缺失突变体除了对拓扑异构酶抑制剂的敏感性增加外，没有明显的表型，这表明SMC在DNA折叠中起作用。类似SMC的SbcC蛋白的缺陷加剧了缺乏SMC的细胞对拓扑异构酶抑制剂的敏感性。我们还表明，耐辐射球菌的SMC蛋白在类核外围形成离散的焦点，这表明SMC可能在局部浓缩DNA。smc基因缺失突变体的表型使我们推测，其他尚未鉴定的蛋白质驱动了耐辐射球菌类核的紧密组织。
