Yeast plasmid segregation: investigation of host/plasmid interactions

2微米环是一个高拷贝数的质粒，稳定地存在于酿酒酵母的大多数菌株的细胞核中。2微米的圆圈是一个“自私的”DNA，借用宿主机器进行复制和分离，以确保它在宿主细胞分裂时很少丢失，同时不会给宿主带来任何好处。我们已经确定SUMO(用一种名为SUMO的泛素相关小蛋白修饰靶蛋白)是一种调节质粒分离的宿主功能。生物化学、分子遗传学和细胞生物学方法将被用来阐明苏莫化和质粒维持之间的联系，并识别和研究质粒借用的其他使其能够遗传的宿主蛋白。荧光显微镜将被用来研究在我们的研究中发现的宿主蛋白的缺失对细胞分裂时多个质粒拷贝的平等分配和对细胞核内的质粒定位的影响。我们的研究还将有助于确定已识别的宿主蛋白参与的细胞过程，并揭示其他蛋白的新功能。该项目将确定2微米圆如何与核的其他组件相互作用，以确保其有效分离。了解酵母质粒如何利用苏莫化和其他宿主过程，可能会揭示其他遗传元素，如病毒是如何维持的，并有助于确定苏莫化在细胞分裂期间染色体忠实分离中所起的关键作用。

The 2µm circle is a high copy-number plasmid stably maintained in the nucleus of most strains of the bakers yeast, Saccharomyces cerevisiae. The 2µm circle is a "selfish" DNA, borrowing host machinery for its replication and segregation to ensure it is seldom lost when the host cell divides, while conferring no advantage to the host. We have identified sumoylation (modification of target proteins with a small ubiquitin-related protein called SUMO) as a host function that regulates plasmid segregation. Biochemical, molecular genetics, and cell biology approaches will be used to elucidate the link between sumoylation and plasmid maintenance and to identify and investigate other host proteins borrowed by the plasmid that enable its inheritance. Fluorescence microscopy will be used to investigate the effect of absence of host proteins identified in our studies on equal partitioning of the multiple plasmid copies at cell division and on plasmid localization within the nucleus. Our studies will also help identify the cellular process to which the identified host proteins contribute and reveal new functions for others. This project will determine how the 2µm circle interacts with other components of the nucleus to ensure its efficient segregation. Understanding how sumoylation and other host processes are exploited by the yeast plasmid may reveal how other genetic elements, such as viruses are maintained and help determine the essential role sumoylation plays in faithful segregation of chromosomes during cell division.