Yasukawa Takehiro, Yang Ming-Yao, Jacobs Howard T, Holt Ian J
MRC-Dunn Human Nutrition Unit, Wellcome Trust-MRC Building, Hills Road, Cambridge CB2 2XY, United Kingdom.
Mol Cell. 2005 Jun 10;18(6):651-62. doi: 10.1016/j.molcel.2005.05.002.
In solid tissues of vertebrates, initiation of mitochondrial DNA replication encompasses a broad zone downstream of the major noncoding region (NCR). In contrast, analysis with two-dimensional agarose gel electrophoresis of mitochondrial DNA replication intermediates in cultured human cells revealed initiation concentrated in the NCR. Mapping of prominent free 5' ends on the heavy strand of mitochondrial DNA identified two clusters of potential start sites. One mapped to the previously assigned origin of strand-asynchronous replication (O(H)); the other lay several hundred nucleotides away from O(H), toward the other end of the NCR. The latter cluster is proposed to be the major site of bidirectional replication initiation on the basis of the following: its prominence is enhanced in cells amplifying mitochondrial DNA after experimentally induced mitochondrial DNA depletion; free 5' ends are found in corresponding positions on the opposite strand; it is transient in nature; and it is associated with bubble arcs.
在脊椎动物的实体组织中，线粒体DNA复制的起始涵盖主要非编码区（NCR）下游的一个广泛区域。相比之下，对培养的人类细胞中线粒体DNA复制中间体进行二维琼脂糖凝胶电泳分析发现，起始集中在NCR。对线粒体DNA重链上突出的游离5'端进行定位，确定了两个潜在起始位点簇。一个定位于先前确定的链异步复制起点（O(H)）；另一个位于离O(H)几百个核苷酸处，朝向NCR的另一端。基于以下几点，后一个簇被认为是双向复制起始的主要位点：在实验诱导线粒体DNA耗竭后线粒体DNA扩增的细胞中，其突出性增强；在相反链的相应位置发现游离5'端；它本质上是短暂的；并且它与泡状弧相关。
