Kim Namil, Song Kiwon
Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul, Korea.
Cell Struct Funct. 2013;38(1):21-30. doi: 10.1247/csf.12014. Epub 2013 Jan 11.
Kinesin family member C1 (KIFC1) is the only member of the minus-end-directed kinesin-14 family in human cells. In cancer cells, KIFC1 plays an essential role in bipolar spindle formation by clustering the multiple poles during mitosis. However, it has not been clearly demonstrated whether KIFC1 also functions to mediate bipolar spindle formation and to maintain genomic stability in normal cells. In this study, by using human primary lung fibroblast IMR-90 cells, we showed that KIFC1 knock-down with lentiviral KIFC1 shRNA induced 17% of cells with multiple microtubule organizing centers (MTOCs) and delayed cyclin A degradation for more than 2 hr in early mitosis. However, these cells eventually carried out mitosis, resulting in 24% of cells with lagging chromosomes and 9% of cells with micronuclei after mitosis. Karyotyping of KIFC1-depleted IMR-90 cells demonstrated that cells with various abnormal numbers of chromosomes are produced. When IMR-90 cells treated with KIFC1 or the control shRNA for 60 hr were compared, 20% less cells were observed in KIFC1-depleted cells without an obvious immediate cell death. As reported for Mad2 depletion in IMR-90 cells, KIFC1-depleted IMR-90 cells showed typical features of senescence, like senescence-associated (SA) β-galactosidase expression, when incubated 6 days or more. However, IMR-90 cells knocked down with both KIFC1 and Mad2 underwent apoptosis, suggesting that KIFC1 and Mad2 likely function in different pathways during mitosis. Taken together, we suggest that KIFC1 plays an essential role for bipolar MTOC formation and maintaining chromosomal stability in the mitosis of human primary fibroblast IMR-90.
驱动蛋白家族成员C1（KIFC1）是人类细胞中负端定向驱动蛋白-14家族的唯一成员。在癌细胞中，KIFC1通过在有丝分裂期间聚集多个纺锤极，在双极纺锤体形成中发挥重要作用。然而，KIFC1是否也在正常细胞中介导双极纺锤体形成并维持基因组稳定性，尚未得到明确证实。在本研究中，我们使用人类原代肺成纤维细胞IMR-90细胞，发现用慢病毒KIFC1短发夹RNA（shRNA）敲低KIFC1可诱导17%的细胞出现多个微管组织中心（MTOC），并在有丝分裂早期使细胞周期蛋白A降解延迟超过2小时。然而，这些细胞最终完成了有丝分裂，导致有丝分裂后24%的细胞出现滞后染色体，9%的细胞出现微核。对KIFC1缺失的IMR-90细胞进行核型分析表明，会产生各种染色体数目异常的细胞。当比较用KIFC1或对照shRNA处理60小时的IMR-90细胞时，在KIFC1缺失的细胞中观察到细胞数量减少了20%，且没有明显的即时细胞死亡。正如在IMR-90细胞中报道的Mad2缺失情况一样，KIFC1缺失的IMR-90细胞在培养6天或更长时间后，表现出典型的衰老特征，如衰老相关（SA）β-半乳糖苷酶表达。然而，同时敲低KIFC1和Mad2的IMR-90细胞发生了凋亡，这表明KIFC1和Mad2在有丝分裂过程中可能在不同途径发挥作用。综上所述，我们认为KIFC1在人类原代成纤维细胞IMR-90的有丝分裂中，对双极MTOC形成和维持染色体稳定性起着至关重要的作用。
