Jayaram M, Li Y Y, Broach J R
Cell. 1983 Aug;34(1):95-104. doi: 10.1016/0092-8674(83)90139-3.
The yeast plasmid 2mu and certain hybrid plasmids constructed from it are maintained stably and at high copy number in yeast cells. By examining various mutant hybrid 2mu plasmids, we show that these properties require the integrity of four plasmid loci. Two of these, designated REP1 and REP2, are active in trans and correspond to two open coding regions of 2mu. The other two loci are active only in cis and correspond to the origin of replication and to a region, designated REP3, located several hundred bp away from the origin and consisting of direct repeats of a 62 bp sequence. We propose that the REP loci constitute a copy control system that overrides normal cellular restriction on plasmid replication and amplifies the plasmid when copy number is low.
酵母质粒2μm及其构建的某些杂种质粒在酵母细胞中能稳定维持且拷贝数很高。通过检测各种突变的杂种2μm质粒，我们发现这些特性需要四个质粒位点的完整性。其中两个位点，命名为REP1和REP2，具有反式活性，对应于2μm的两个开放编码区。另外两个位点仅具有顺式活性，分别对应于复制起点和一个称为REP3的区域，该区域位于距起点几百个碱基对处，由一个62bp序列的直接重复序列组成。我们提出，REP位点构成了一个拷贝控制系统，该系统能克服细胞对质粒复制的正常限制，并在拷贝数较低时扩增质粒。
