Sau Soumitra, Conrad Michael N, Lee Chih-Ying, Kaback David B, Dresser Michael E, Jayaram Makkuni
Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712.
Program in Cell Cycle and Cancer Biology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104.
J Cell Biol. 2014 Jun 9;205(5):643-61. doi: 10.1083/jcb.201312002.
The chromosome-like mitotic stability of the yeast 2 micron plasmid is conferred by the plasmid proteins Rep1-Rep2 and the cis-acting locus STB, likely by promoting plasmid-chromosome association and segregation by hitchhiking. Our analysis reveals that stable plasmid segregation during meiosis requires the bouquet proteins Ndj1 and Csm4. Plasmid relocalization from the nuclear interior in mitotic cells to the periphery at or proximal to telomeres rises from early meiosis to pachytene. Analogous to chromosomes, the plasmid undergoes Csm4- and Ndj1-dependent rapid prophase movements with speeds comparable to those of telomeres. Lack of Ndj1 partially disrupts plasmid-telomere association without affecting plasmid colocalization with the telomere-binding protein Rap1. The plasmid appears to engage a meiosis-specific motor that orchestrates telomere-led chromosome movements for its telomere-associated segregation during meiosis I. This hitherto uncharacterized mode of germ-line transmission by a selfish genetic element signifies a mechanistic variation within the shared theme of chromosome-coupled plasmid segregation during mitosis and meiosis.
酵母2微米质粒的染色体样有丝分裂稳定性由质粒蛋白Rep1-Rep2和顺式作用位点STB赋予，可能是通过搭便车促进质粒-染色体的关联和分离。我们的分析表明，减数分裂期间稳定的质粒分离需要成束蛋白Ndj1和Csm4。从有丝分裂细胞的核内部到减数分裂早期至粗线期端粒处或近端的周边，质粒重新定位。与染色体类似，质粒经历依赖于Csm4和Ndj1的快速前期移动，其速度与端粒相当。缺乏Ndj1会部分破坏质粒-端粒关联，但不影响质粒与端粒结合蛋白Rap1的共定位。质粒似乎参与了一种减数分裂特异性的运动机制，该机制在减数分裂I期间协调由端粒引导的染色体运动，以实现其与端粒相关的分离。这种自私遗传元件迄今未被表征的种系传递模式，标志着有丝分裂和减数分裂期间染色体偶联质粒分离这一共同主题内的一种机制变异。
