Department of Biochemistry and Molecular Biology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD 20814.
Mol Biol Cell. 2020 Jun 1;31(12):1289-1301. doi: 10.1091/mbc.E20-03-0166. Epub 2020 Apr 8.
The multi-component cytoplasmic dynein transports cellular cargoes with the help of another multi-component complex dynactin, but we do not know enough about factors that may affect the assembly and functions of these proteins. From a genetic screen for mutations affecting early-endosome distribution in , we identified the mutation in Prp40A, a homologue of Prp40, an essential RNA-splicing factor in the budding yeast. Prp40A is not essential for splicing, although it associates with the nuclear splicing machinery. The mutant is much healthier than the ∆ mutant, but both mutants exhibit similar defects in dynein-mediated early-endosome transport and nuclear distribution. In the mutant, the frequency but not the speed of dynein-mediated early-endosome transport is decreased, which correlates with a decrease in the microtubule plus-end accumulations of dynein and dynactin. Within the dynactin complex, the actin-related protein Arp1 forms a mini-filament. In a pull-down assay, the amount of Arp1 pulled down with its pointed-end protein Arp11 is lowered in the mutant. In addition, we found from published interactome data that a mammalian Prp40 homologue PRPF40A interacts with Arp1. Thus, Prp40 homologues may regulate the assembly or function of dynein-dynactin and their mechanisms deserve to be further studied.
多组分细胞质动力蛋白在另一个多组分复合物 dynactin 的帮助下运输细胞货物，但我们对可能影响这些蛋白质组装和功能的因素了解还不够。在一项针对影响早期内体分布的突变的遗传筛选中，我们在 中发现了 Prp40A 的突变，Prp40A 是芽殖酵母中必需的 RNA 剪接因子 Prp40 的同源物。虽然 Prp40A 与核剪接机制相关，但它不是剪接所必需的。突变体比 ∆ 突变体更健康，但这两种突变体都表现出类似的动力蛋白介导的早期内体运输和核分布缺陷。在 突变体中，动力蛋白介导的早期内体运输的频率而不是速度降低，这与动力蛋白和 dynactin 的微管正端积累减少有关。在 dynactin 复合物中，肌动蛋白相关蛋白 Arp1 形成一个微丝。在下拉测定中，与它的尖端蛋白 Arp11 一起下拉的 Arp1 量在 突变体中降低。此外，我们从已发表的相互作用组数据中发现，一种哺乳动物 Prp40 同源物 PRPF40A 与 Arp1 相互作用。因此，Prp40 同源物可能调节动力蛋白 dynactin 的组装或功能，它们的机制值得进一步研究。
