Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
J Cell Biol. 2013 Jan 21;200(2):151-61. doi: 10.1083/jcb.201206142. Epub 2013 Jan 14.
Many mitotic factors were shown to be activated by Ran guanosine triphosphatase. Previous studies in Xenopus laevis egg extracts and in highly proliferative cells showed that mitotic chromosomes were surrounded by steep Ran guanosine triphosphate (GTP) concentration gradients, indicating that RanGTP-activated factors promote spindle assembly around chromosomes. However, the mitotic role of Ran in normal differentiated cells is not known. In this paper, we show that although the steep mitotic RanGTP gradients were present in rapidly growing cell lines and were required for chromosome congression in mitotic HeLa cells, the gradients were strongly reduced in slow-growing primary cells, such as HFF-1 fibroblasts. The overexpression of RCC1, the guanine nucleotide exchange factor for Ran, induced steeper mitotic RanGTP gradients in HFF-1 cells, showing the critical role of RCC1 levels in the regulation of mitosis by Ran. Remarkably, in vitro fusion of HFF-1 cells produced cells with steep mitotic RanGTP gradients comparable to HeLa cells, indicating that chromosomal gain can promote mitosis in aneuploid cancer cells via Ran.
许多有丝分裂因子被证明可以被 Ran GTP 酶激活。先前在非洲爪蟾卵提取物和高度增殖细胞中的研究表明，有丝分裂染色体周围存在陡峭的 Ran GTP（GTP）浓度梯度，表明 RanGTP 激活因子促进纺锤体在染色体周围组装。然而，Ran 在正常分化细胞中的有丝分裂作用尚不清楚。本文显示，尽管在快速生长的细胞系中存在陡峭的有丝分裂 RanGTP 梯度，并且这些梯度对于有丝分裂 HeLa 细胞中的染色体向心性收缩是必需的，但在生长缓慢的原代细胞（如 HFF-1 成纤维细胞）中，这些梯度强烈降低。RCC1 的过表达，Ran 的鸟嘌呤核苷酸交换因子，在 HFF-1 细胞中诱导更陡峭的有丝分裂 RanGTP 梯度，表明 RCC1 水平在 Ran 调节有丝分裂中起着关键作用。值得注意的是，HFF-1 细胞的体外融合产生了具有与 HeLa 细胞相当的陡峭有丝分裂 RanGTP 梯度的细胞，表明染色体增益可以通过 Ran 促进非整倍体癌细胞的有丝分裂。
