Instituto de Microbiología Bioquímica, CSIC/Universidad de Salamanca, Edificio Departamental, Salamanca, Spain.
EMBO J. 2010 Mar 3;29(5):934-42. doi: 10.1038/emboj.2009.411. Epub 2010 Jan 21.
DNA replication origins (ORI) in Schizosaccharomyces pombe colocalize with adenine and thymine (A+T)-rich regions, and earlier analyses have established a size from 0.5 to over 3 kb for a DNA fragment to drive replication in plasmid assays. We have asked what are the requirements for ORI function in the chromosomal context. By designing artificial ORIs, we have found that A+T-rich fragments as short as 100 bp without homology to S. pombe DNA are able to initiate replication in the genome. On the other hand, functional dissection of endogenous ORIs has revealed that some of them span a few kilobases and include several modules that may be as short as 25-30 contiguous A+Ts capable of initiating replication from ectopic chromosome positions. The search for elements with these characteristics across the genome has uncovered an earlier unnoticed class of low-efficiency ORIs that fire late during S phase. These results indicate that ORI specification and dynamics varies widely in S. pombe, ranging from very short elements to large regions reminiscent of replication initiation zones in mammals.
酿酒酵母的 DNA 复制起始点（ORI）与腺嘌呤和胸腺嘧啶（A+T）丰富区域共定位，早期的分析已经确定了一个 DNA 片段的大小，从 0.5 到超过 3kb，可以在质粒实验中驱动复制。我们已经询问了在染色体背景下 ORI 功能的要求。通过设计人工 ORI，我们发现，短至 100bp 的 A+T 丰富片段，与酿酒酵母 DNA 没有同源性，也能够在基因组中启动复制。另一方面，对内源性 ORI 的功能剖析表明，其中一些跨越几个千碱基，包括几个模块，这些模块可能短至 25-30 个连续的 A+T，能够从异位染色体位置启动复制。在整个基因组中搜索具有这些特征的元件，揭示了一类以前未被注意到的低效率 ORI，它们在 S 期后期才开始活跃。这些结果表明，酿酒酵母的 ORI 特异性和动力学变化很大，从非常短的元件到类似于哺乳动物复制起始区的大区域。
