Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, TX 77008, USA.
Mol Biol Cell. 2013 Sep;24(17):2655-67. doi: 10.1091/mbc.E13-01-0061. Epub 2013 Jul 17.
Neuroepithelial transforming gene 1 (Net1) is a RhoA-subfamily-specific guanine nucleotide exchange factor that is overexpressed in multiple human cancers and is required for proliferation. Molecular mechanisms underlying its role in cell proliferation are unknown. Here we show that overexpression or knockdown of Net1 causes mitotic defects. Net1 is required for chromosome congression during metaphase and generation of stable kinetochore microtubule attachments. Accordingly, inhibition of Net1 expression results in spindle assembly checkpoint activation. The ability of Net1 to control mitosis is independent of RhoA or RhoB activation, as knockdown of either GTPase does not phenocopy effects of Net1 knockdown on nuclear morphology, and effects of Net1 knockdown are effectively rescued by expression of catalytically inactive Net1. We also observe that Net1 expression is required for centrosomal activation of p21-activated kinase and its downstream kinase Aurora A, which are critical regulators of centrosome maturation and spindle assembly. These results identify Net1 as a novel regulator of mitosis and indicate that altered expression of Net1, as occurs in human cancers, may adversely affect genomic stability.
神经上皮转化基因 1（Net1）是一种 RhoA 亚家族特异性鸟嘌呤核苷酸交换因子，在多种人类癌症中过度表达，是增殖所必需的。其在细胞增殖中的作用的分子机制尚不清楚。在这里，我们表明 Net1 的过表达或敲低会导致有丝分裂缺陷。Net1 在中期染色体向心运动和稳定的动粒微管附着的产生中是必需的。因此，抑制 Net1 的表达会导致纺锤体组装检查点的激活。Net1 控制有丝分裂的能力不依赖于 RhoA 或 RhoB 的激活，因为敲低任何一种 GTPase 都不会模拟 Net1 敲低对核形态的影响，并且 Net1 敲低的影响可以通过表达无催化活性的 Net1 有效地挽救。我们还观察到 Net1 的表达对于 p21 激活激酶及其下游激酶 Aurora A 的中心体激活是必需的，后者是中心体成熟和纺锤体组装的关键调节因子。这些结果表明 Net1 是有丝分裂的一个新的调节因子，并表明 Net1 的表达改变，如在人类癌症中发生的那样，可能会对基因组稳定性产生不利影响。
