Program in Molecular and Computational Biology, University of Southern California, Los Angeles, CA, USA.
Cell Cycle. 2011 Jan 15;10(2):323-36. doi: 10.4161/cc.10.2.14552.
Heterochromatin in S. pombe is associated with gene silencing at telomeres, the mating locus and centromeres. The compact heterochromatin structure raises the question how it unpacks and reforms during DNA replication. We show that the essential DNA replication factor Cdc18 (CDC6) associates with heterochromatin protein 1 (Swi6) in vivo and in vitro. Biochemical mapping and mutational analysis of the association domains show that the N-terminus of Cdc18 interacts with the chromoshadow domain of Swi6. Mutations in Swi6 that disrupt this interaction disrupt silencing and delay replication in the centromere. A mutation cdc18-I43A that reduces Cdc18 association with Swi6 has no silencing defect at the centromere, but changes Swi6 distribution and accelerates the timing of centromere replication. We suggest that fine tuning of Swi6 association at replication origins is important for negative as well as positive control of replication initiation.
在 S. pombe 中，异染色质与端粒、交配位点和着丝粒的基因沉默有关。紧凑的异染色质结构提出了一个问题，即在 DNA 复制过程中它如何解压缩和重组。我们表明，必需的 DNA 复制因子 Cdc18（CDC6）在体内和体外与异染色质蛋白 1（Swi6）相关联。关联域的生化作图和突变分析表明，Cdc18 的 N 端与 Swi6 的染色质阴影域相互作用。破坏这种相互作用的 Swi6 突变会破坏沉默并延迟着丝粒的复制。降低 Cdc18 与 Swi6 关联的突变 cdc18-I43A 在着丝粒处没有沉默缺陷，但会改变 Swi6 的分布并加速着丝粒复制的时间。我们认为，在复制起点处精细调节 Swi6 的关联对于复制起始的负调控和正调控都很重要。
