Initiation of DNA replication occurs at specialized regions along chromosomes called origins. The knowledge of replication origins is imperative to understand regulation of DNA replication. The properties of replication origins in the pathogenic budding yeast Candida albicans remain enigmatic in the absence of the knowledge of authentic chromosomal origins. Earlier, we identified centromere proximal (pCEN) chromosomal origins on chromosomes 5 and 7 of C. albicans. Here, we identify another centromere-distal (dCEN) chromosomal origin by two-dimensional agarose gel electrophoresis corresponding to a previously reported autonomously replicating sequence (ARS), CARS2. We show that all the identified chromosomal origins are bound by C. albicans homologs of conserved pre-replication complex proteins Orc2 and Mcm2. Previous reports from our lab and others have shown that there is a strong inter-relationship between centromere function and pericentric origin activity, suggesting that these origins are epigenetically regulated. However, we find that short intergenic regions corresponding to each of these origins functions as an ARS element in circular plasmids. Further, we use the novel strategy of in vivo gap repair to demonstrate that circular ARS plasmids can exist independently in vivo in C. albicans. Taken together, these results show that DNA sequence underlies the function of both centromere proximal and centromere distal chromosomal origins in C. albicans.

中文翻译：

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白色念珠菌的染色体复制起点是遗传定义的，无论其染色体背景如何

DNA复制的起始发生在沿着染色体的特定区域，称为起源。复制起点的知识对于理解DNA复制的调控至关重要。在缺乏真正的染色体起源的知识的情况下，致病的发芽酵母白色念珠菌中的复制起源的特性仍然是谜。之前，我们在白色念珠菌的5号和7号染色体上鉴定了着丝粒近端（pCEN）染色体起源。在这里，我们通过二维琼脂糖凝胶电泳确定另一个着丝粒-远端（dCEN）染色体起源，它对应于先前报道的自主复制序列（ARS）CARS2。我们表明，所有已鉴定的染色体起源均由保守复制前复杂蛋白Orc2和Mcm2的白色念珠菌同源物结合。我们实验室和其他研究机构先前的报告表明，着丝粒功能与周围中心起源活动之间存在很强的相互关系，表明这些起源是表观遗传调控的。但是，我们发现对应于这些起源中的每一个的短的基因间隔区在环状质粒中起ARS元件的作用。此外，我们使用体内缺口修复的新策略来证明环状ARS质粒可以在白色念珠菌体内独立存在。综上所述，这些结果表明，DNA序列是白色念珠菌中着丝粒近端和着丝粒远端染色体起源的功能的基础。我们发现对应于这些起源中的每一个的短的基因间隔区在环状质粒中起着ARS元件的作用。此外，我们使用体内缺口修复的新策略来证明环状ARS质粒可以在白色念珠菌体内独立存在。综上所述，这些结果表明，DNA序列是白色念珠菌中着丝粒近端和着丝粒远端染色体起源的功能的基础。我们发现对应于这些起源中的每个起源的短的基因间隔区域在圆形质粒中充当ARS元件。此外，我们使用体内缺口修复的新策略来证明环状ARS质粒可以在白色念珠菌体内独立存在。综上所述，这些结果表明，DNA序列是白色念珠菌中着丝粒近端和着丝粒远端染色体起源的功能的基础。