Department of Microbiology, University of Freiburg, Schänzle Strasse 1, 79104 Freiburg, Germany.
Nucleic Acids Res. 2010 Jan;38(2):455-66. doi: 10.1093/nar/gkp909. Epub 2009 Nov 11.
Bacillus subtilis and most Gram positive bacteria possess four SMC like proteins: SMC, SbcC, RecN and the product of the yhaN gene, termed SbcE. SbcE is most similar to SbcC but contains a unique central domain. We show that SbcE plays a role during transformation in competent cells and in DNA double-strand break (DSB) repair. The phenotypes were strongly exacerbated by the additional deletion of recN or of sbcC, suggesting that all three proteins act upstream of RecA and provide distinct avenues for presynapsis. SbcE accumulated at the cell poles in competent cells, and localized as a discrete focus on the nucleoids in 10% of growing cells. This number moderately increased after treatment with DNA damaging agents and in the absence of RecN or of SbcC. Damage-induced foci of SbcE arose early after induction of DNA damage and rarely colocalized with the replication machinery. Our work shows that SMC-like proteins in B. subtilis play roles at different subcellular sites during DNA repair. SbcC operates at breaks occurring at the replication machinery, whereas RecN and SbcE function mainly, but not exclusively, at DSBs arising elsewhere on the chromosome. In agreement with this idea, we found that RecN-YFP damage-induced assemblies also arise in the absence of ongoing replication.
枯草芽孢杆菌和大多数革兰氏阳性菌拥有四种类似 SMC 的蛋白质：SMC、SbcC、RecN 和 yhaN 基因产物，称为 SbcE。SbcE 与 SbcC 最相似，但含有独特的中心结构域。我们发现 SbcE 在感受态细胞中的转化和 DNA 双链断裂 (DSB) 修复中发挥作用。当 recN 或 sbcC 的缺失进一步增强表型时，表明这三种蛋白质都在前 RecA 作用，提供了不同的预联会途径。SbcE 在感受态细胞中积累在细胞两极，并在 10%的生长细胞中定位于核区的离散焦点。在用 DNA 损伤剂处理后，这个数字适度增加，而在没有 RecN 或 SbcC 的情况下则增加更多。损伤诱导的 SbcE 焦点在 DNA 损伤诱导后早期出现，很少与复制机制共定位。我们的工作表明，枯草芽孢杆菌中的 SMC 样蛋白在 DNA 修复过程中在不同的亚细胞部位发挥作用。SbcC 在复制机制上发生的断裂处起作用，而 RecN 和 SbcE 主要（但不是唯一）在染色体上其他地方出现的 DSB 处起作用。与这一观点一致，我们发现即使没有正在进行的复制，RecN-YFP 损伤诱导的组装也会出现。
