Ben-Yehuda Sigal, Fujita Masya, Liu Xiaole Shirley, Gorbatyuk Boris, Skoko Dunja, Yan Jie, Marko John F, Liu Jun S, Eichenberger Patrick, Rudner David Z, Losick Richard
Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, Massachusetts 02138, USA.
Mol Cell. 2005 Mar 18;17(6):773-82. doi: 10.1016/j.molcel.2005.02.023.
Chromosome segregation during sporulation in Bacillus subtilis involves the anchoring of sister chromosomes to opposite ends of the cell. Anchoring is mediated by RacA, which acts as a bridge between a centromere-like element in the vicinity of the origin of replication and the cell pole. To define this element we mapped RacA binding sites by performing chromatin immunoprecipitation in conjunction with gene microarray analysis. RacA preferentially bound to 25 regions spread over 612 kb across the origin portion of the chromosome. Computational and biochemical analysis identified a GC-rich, inverted 14 bp repeat as the recognition sequence. Experiments with single molecules of DNA demonstrated that RacA can condense nonspecific DNA dramatically against appreciable forces to form a highly stable protein-DNA complex. We propose that interactions between DNA bound RacA molecules cause the centromere-like element to fold up into a higher order complex that fastens the chromosome to the cell pole.
枯草芽孢杆菌孢子形成过程中的染色体分离涉及姐妹染色体锚定到细胞的相对两端。这种锚定由RacA介导，RacA在复制起点附近的一个着丝粒样元件与细胞极之间起桥梁作用。为了确定这个元件，我们通过结合基因微阵列分析进行染色质免疫沉淀来绘制RacA结合位点。RacA优先结合在染色体起点部分跨越612 kb的25个区域。计算和生化分析确定了一个富含GC的14 bp反向重复序列作为识别序列。对单分子DNA的实验表明，RacA能够在相当大的力作用下显著凝聚非特异性DNA，形成高度稳定的蛋白质-DNA复合物。我们提出，结合了DNA的RacA分子之间的相互作用会使着丝粒样元件折叠成一个更高阶的复合物，从而将染色体固定到细胞极上。
