Veit B E, Fangman W L
Department of Genetics, University of Washington, Seattle 98195.
Mol Cell Biol. 1988 Nov;8(11):4949-57. doi: 10.1128/mcb.8.11.4949-4957.1988.
The 2 micron plasmid of Saccharomyces cerevisiae is maintained by the action of plasmid-encoded gene products that control copy number and promote equipartition of plasmid copies at cell division. We show that the REP1 and REP2 plasmid-encoded gene products are master regulators that act in concert to autoregulate the level of their own transcripts and to regulate transcript levels of the FLP gene that promotes plasmid copy amplification. REP1 and REP2 are also shown to repress transcription at REP3, the cis-acting site essential for plasmid equipartitioning. We propose a model in which REP3 acts by dislodging transcription apparatuses that otherwise cause plasmid molecules to adhere to the mother nucleus and segregate asymmetrically. On the basis of their ability to generate specific chromatin structures, we also propose that the REP1 and REP2 gene products interact with different specific sequences found iterated in the 2 micron plasmid.
酿酒酵母的2微米质粒通过质粒编码基因产物的作用得以维持，这些基因产物控制着拷贝数，并在细胞分裂时促进质粒拷贝的均等分配。我们发现，质粒编码的REP1和REP2基因产物是主要调节因子，它们协同作用以自动调节自身转录本的水平，并调节促进质粒拷贝扩增的FLP基因的转录本水平。REP1和REP2还被证明可抑制REP3处的转录，REP3是质粒均等分配所必需的顺式作用位点。我们提出了一个模型，其中REP3通过移除转录装置来发挥作用，否则这些转录装置会导致质粒分子附着于母细胞核并进行不对称分离。基于它们产生特定染色质结构的能力，我们还提出REP1和REP2基因产物与在2微米质粒中重复出现的不同特定序列相互作用。
