Tsuchiya E, Hosotani T, Miyakawa T
Department of Fermentation Technology, Faculty of Engineering, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8527, Japan.
Nucleic Acids Res. 1998 Jul 1;26(13):3286-92. doi: 10.1093/nar/26.13.3286.
The NPS1/STH1 gene encodes a nuclear protein essential for the progression of G2/M phase in Saccharomyces cerevisiae . Nps1p shares homology to Snf2/Swi2p, a subunit of a protein complex known as the SNF/SWI complex. Recently, Nps1p was found to be a component of a protein complex termed RSC (3) essential for mitotic growth, whereas its function is unknown. We isolated a temperature-sensitive mutant allele of NPS1 , nps1-105, and found that the mutation increases the sensitivity to thiabendazole (TBZ). At the restrictive temperature, nps1-105 arrested at the G2/M phase in MAD1-dependent manner and missegregated the mini-chromosome with higher frequency than the wild type cells. The nuclease digestion of the chromatin of the mutant cells revealed that the mutation causes the alteration of the chromatin structure around centromeres at the restrictive temperature. The results suggested that, in the nps1-105 mutant, impaired chromatin structure surrounding centromeres may lead to an impairment of kinetochore function and the cells arrest at G2/M phase through the spindle-assembly checkpoint system.
NPS1/STH1基因编码一种对酿酒酵母中G2/M期进程至关重要的核蛋白。Nps1p与Snf2/Swi2p具有同源性，Snf2/Swi2p是一种名为SNF/SWI复合体的蛋白质复合体的一个亚基。最近，Nps1p被发现是一种名为RSC（3）的蛋白质复合体的组成部分，该复合体对有丝分裂生长至关重要，但其功能尚不清楚。我们分离出了NPS1的一个温度敏感突变等位基因nps1-105，并发现该突变增加了对噻苯咪唑（TBZ）的敏感性。在限制温度下，nps1-105以依赖MAD1的方式在G2/M期停滞，并且与野生型细胞相比，以更高的频率错误分离小染色体。对突变细胞染色质的核酸酶消化显示，该突变在限制温度下导致着丝粒周围染色质结构的改变。结果表明，在nps1-105突变体中，着丝粒周围受损的染色质结构可能导致动粒功能受损，并且细胞通过纺锤体组装检查点系统在G2/M期停滞。
