Pryzhkova Marina V, Jordan Philip W
Department of Biochemistry and Molecular Biology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205, USA.
Department of Biochemistry and Molecular Biology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205, USA
J Cell Sci. 2016 Apr 15;129(8):1619-34. doi: 10.1242/jcs.179036. Epub 2016 Feb 26.
Correct duplication of stem cell genetic material and its appropriate segregation into daughter cells are requisites for tissue, organ and organism homeostasis. Disruption of stem cell genomic integrity can lead to developmental abnormalities and cancer. Roles of the Smc5/6 structural maintenance of chromosomes complex in pluripotent stem cell genome maintenance have not been investigated, despite its important roles in DNA synthesis, DNA repair and chromosome segregation as evaluated in other model systems. Using mouse embryonic stem cells (mESCs) with a conditional knockout allele of Smc5, we showed that Smc5 protein depletion resulted in destabilization of the Smc5/6 complex, accumulation of cells in G2 phase of the cell cycle and apoptosis. Detailed assessment of mitotic mESCs revealed abnormal condensin distribution and perturbed chromosome segregation, accompanied by irregular spindle morphology, lagging chromosomes and DNA bridges. Mutation of Smc5 resulted in retention of Aurora B kinase and enrichment of condensin on chromosome arms. Furthermore, we observed reduced levels of Polo-like kinase 1 at kinetochores during mitosis. Our study reveals crucial requirements of the Smc5/6 complex during cell cycle progression and for stem cell genome maintenance.
干细胞遗传物质的正确复制及其向子细胞的适当分离是组织、器官和生物体稳态的必要条件。干细胞基因组完整性的破坏会导致发育异常和癌症。尽管在其他模型系统中评估发现，染色体结构维持蛋白复合体Smc5/6在DNA合成、DNA修复和染色体分离中发挥重要作用，但尚未对其在多能干细胞基因组维持中的作用进行研究。利用具有Smc5条件性敲除等位基因的小鼠胚胎干细胞（mESCs），我们发现Smc5蛋白缺失导致Smc5/6复合体不稳定，细胞在细胞周期的G2期积累并发生凋亡。对有丝分裂期mESCs的详细评估显示，凝缩蛋白分布异常且染色体分离受到干扰，同时伴有纺锤体形态不规则、染色体滞后和DNA桥。Smc5突变导致Aurora B激酶保留以及凝缩蛋白在染色体臂上富集。此外，我们观察到有丝分裂期间动粒处Polo样激酶1水平降低。我们的研究揭示了Smc5/6复合体在细胞周期进程和干细胞基因组维持过程中的关键需求。
