Center for Global Infectious Disease Research, Seattle Children's Research Institute , Seattle, WA, USA.
Laboratory of Cellular and Structural Biology, The Rockefeller University , New York, NY, USA.
J Cell Biol. 2023 Sep 4;222(9). doi: 10.1083/jcb.202207060. Epub 2023 Jun 26.
The nuclear pore complex (NPC) physically interacts with chromatin and regulates gene expression. The Saccharomyces cerevisiae inner ring nucleoporin Nup170 has been implicated in chromatin organization and the maintenance of gene silencing in subtelomeric regions. To gain insight into how Nup170 regulates this process, we used protein-protein interactions, genetic interactions, and transcriptome correlation analyses to identify the Ctf18-RFC complex, an alternative proliferating cell nuclear antigen (PCNA) loader, as a facilitator of the gene regulatory functions of Nup170. The Ctf18-RFC complex is recruited to a subpopulation of NPCs that lack the nuclear basket proteins Mlp1 and Mlp2. In the absence of Nup170, PCNA levels on DNA are reduced, resulting in the loss of silencing of subtelomeric genes. Increasing PCNA levels on DNA by removing Elg1, which is required for PCNA unloading, rescues subtelomeric silencing defects in nup170Δ. The NPC, therefore, mediates subtelomeric gene silencing by regulating PCNA levels on DNA.
核孔复合体（NPC）与染色质相互作用，并调节基因表达。酿酒酵母内环核孔蛋白 Nup170 被认为与染色质组织以及端粒区基因沉默的维持有关。为了深入了解 Nup170 如何调节这一过程，我们利用蛋白质-蛋白质相互作用、遗传相互作用和转录组相关性分析，鉴定出 Ctf18-RFC 复合物，即一种替代增殖细胞核抗原（PCNA）加载器，是 Nup170 基因调控功能的促进剂。Ctf18-RFC 复合物被招募到缺乏核篮蛋白 Mlp1 和 Mlp2 的 NPC 亚群中。在没有 Nup170 的情况下，DNA 上的 PCNA 水平降低，导致端粒基因沉默的丧失。通过去除 Elg1 增加 DNA 上的 PCNA 水平，Elg1 是 PCNA 卸载所必需的，挽救了 nup170Δ中端粒沉默缺陷。因此，NPC 通过调节 DNA 上的 PCNA 水平介导端粒基因沉默。
