Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America.
PLoS Genet. 2010 May 13;6(5):e1000946. doi: 10.1371/journal.pgen.1000946.
Eukaryotic chromosomes initiate DNA synthesis from multiple replication origins. The machinery that initiates DNA synthesis is highly conserved, but the sites where the replication initiation proteins bind have diverged significantly. Functional comparative genomics is an obvious approach to study the evolution of replication origins. However, to date, the Saccharomyces cerevisiae replication origin map is the only genome map available. Using an iterative approach that combines computational prediction and functional validation, we have generated a high-resolution genome-wide map of DNA replication origins in Kluyveromyces lactis. Unlike other yeasts or metazoans, K. lactis autonomously replicating sequences (KlARSs) contain a 50 bp consensus motif suggestive of a dimeric structure. This motif is necessary and largely sufficient for initiation and was used to dependably identify 145 of the up to 156 non-repetitive intergenic ARSs projected for the K. lactis genome. Though similar in genome sizes, K. lactis has half as many ARSs as its distant relative S. cerevisiae. Comparative genomic analysis shows that ARSs in K. lactis and S. cerevisiae preferentially localize to non-syntenic intergenic regions, linking ARSs with loci of accelerated evolutionary change.
真核染色体从多个复制起点启动 DNA 合成。启动 DNA 合成的机制高度保守,但复制起始蛋白结合的位点已经有很大的差异。功能比较基因组学是研究复制起点进化的一种明显方法。然而,迄今为止,酿酒酵母的复制起点图谱是唯一可用的基因组图谱。我们采用一种迭代方法,结合计算预测和功能验证,生成了克鲁维酵母 DNA 复制起点的高分辨率全基因组图谱。与其他酵母或后生动物不同,乳克鲁维酵母自主复制序列 (KlARSs) 含有一个 50 个碱基对的共识基序,提示二聚体结构。该基序对于起始是必需的,并且在很大程度上是充分的,可用于可靠地识别多达 156 个非重复基因间 ARS 中的 145 个,这些 ARS 预计存在于乳克鲁维酵母基因组中。尽管基因组大小相似,但乳克鲁维酵母的 ARS 数量是其远亲酿酒酵母的一半。比较基因组分析表明,乳克鲁维酵母和酿酒酵母的 ARS 优先定位于非同源基因间区域,将 ARS 与加速进化变化的基因座联系起来。