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大肠杆菌姐妹染色单体分离包括一个突然的全局转变,同时释放后期分裂的姐妹连接点。

Escherichia coli sister chromosome separation includes an abrupt global transition with concomitant release of late-splitting intersister snaps.

机构信息

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.

出版信息

Proc Natl Acad Sci U S A. 2011 Feb 15;108(7):2765-70. doi: 10.1073/pnas.1019593108. Epub 2011 Jan 31.

Abstract

The basis for segregation of sister chromosomes in bacteria is not established. We show here that two discrete ~150-kb regions, both located early in the right replichore, exhibit prolonged juxtaposition of sister loci, for 20 and 30 min, respectively, after replication. Flanking regions, meanwhile, separate. Thus, the two identified regions comprise specialized late-splitting intersister connections or snaps. Sister snap loci separate simultaneously in both snap regions, concomitant with a major global nucleoid reorganization that results in emergence of a bilobed nucleoid morphology. Split snap loci move rapidly apart to a separation distance comparable with one-half the length of the nucleoid. Concomitantly, at already split positions, sister loci undergo further separation to a comparable distance. The overall consequence of these and other effects is that thus far replicated sister chromosomes become spatially separated (individualized) into the two nucleoid lobes, while the terminus region (and likely, all unreplicated portions of the chromosome) moves to midcell. These and other findings imply that segregation of Escherichia coli sister chromosomes is not a smooth continuous process but involves at least one and likely, two major global transition(s). The presented patterns further suggest that accumulation of internal intranucleoid forces and constraining of these forces by snaps play central roles in global chromosome dynamics. They are consistent with and supportive of our previous proposals that individualization of sisters in E. coli is driven primarily by internally generated pushing forces and is directly analogous to sister individualization at the prophase to prometaphase transition of the eukaryotic cell cycle.

摘要

细菌中姐妹染色体分离的基础尚未确定。我们在这里表明,两个离散的~150kb 区域都位于右复制子的早期,在复制后分别有 20 分钟和 30 分钟的姐妹基因座的长时间并列。与此同时,侧翼区域分离。因此,这两个已识别的区域包含专门的晚期分裂姐妹连接或连接点。姐妹连接点同时在两个连接点区域中分离,伴随着一个主要的全局核小体重组,导致核小体形态出现双叶状。分裂的连接点迅速分开,分离距离与核小体长度的一半相当。同时,在已经分裂的位置,姐妹基因座进一步分离到类似的距离。这些和其他效应的总体结果是,迄今为止复制的姐妹染色体在空间上被分离(个体化)成两个核小体叶,而末端区域(可能还有染色体的所有未复制部分)移动到细胞中部。这些和其他发现表明,大肠杆菌姐妹染色体的分离不是一个平滑连续的过程,而是至少涉及一个,可能还有两个主要的全局转变。所呈现的模式进一步表明,核内内部力的积累和连接点对这些力的约束在全局染色体动力学中起着核心作用。它们与我们之前的提议一致,并支持我们的提议,即在大肠杆菌中姐妹的个体化主要是由内部产生的推力驱动的,并且与真核细胞周期的前期到前中期转变中姐妹的个体化直接类似。

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