Wu Guikai, Chen Phang-Lang
Department of Biological Chemistry, School of Medicine, D268 Medical Science I, University of California, Irvine, CA 92697, USA.
Biochem Biophys Res Commun. 2008 Aug 1;372(3):454-8. doi: 10.1016/j.bbrc.2008.05.065. Epub 2008 May 23.
Human Kif4A is a member of the Kinesin-4 family of kinesins. Kif4A is thought to be a bona fide chromokinesin because it possesses a motor domain and associates with condensed chromosomes during mitosis. Genetic deletion of Kif4A promotes tumorigenic phenotypes in mouse embryonic cells. Kif4A is critical for mitotic regulation including chromosome condensation, spindle organization and cytokinesis. However, the precise chromatin-binding domain of Kif4A has not been characterized. Herein, we report the identification of two conserved motifs critical for chromatin-binding: the first leucine Zip motif (Zip1) of a leucine Zip/Basic/leucine Zip region (ZBZ) previously thought to be a nuclear localization signal (NLS), and a cysteine-rich (CR) motif within the C-terminal region of Kif4A. Furthermore, by depleting endogenous Kif4A via RNAi and concurrently expressing RNAi-resistant Kif4A versions, we observed that wild type Kif4A, but not the mutants deficient in DNA-binding (Zip1 or CR deleted) or ATPase activity (K94A point mutant), was able to rescue the RNAi-elicited abnormal mitotic profile. Taken together, our results show that both the Zip1 and CR motifs are important for Kif4A chromatin-binding and its mitotic function.
人类Kif4A是驱动蛋白-4家族的成员。Kif4A被认为是一种真正的染色体驱动蛋白，因为它具有一个运动结构域，并且在有丝分裂期间与浓缩染色体相关联。Kif4A的基因缺失会促进小鼠胚胎细胞中的致瘤表型。Kif4A对于包括染色体浓缩、纺锤体组织和胞质分裂在内的有丝分裂调控至关重要。然而，Kif4A精确的染色质结合结构域尚未得到表征。在此，我们报告了对两个对染色质结合至关重要的保守基序的鉴定：先前被认为是核定位信号（NLS）的亮氨酸拉链/碱性/亮氨酸拉链区域（ZBZ）的第一个亮氨酸拉链基序（Zip1），以及Kif4A C末端区域内的富含半胱氨酸（CR）基序。此外，通过RNA干扰耗尽内源性Kif4A并同时表达抗RNA干扰的Kif4A变体，我们观察到野生型Kif4A能够挽救RNA干扰引发的异常有丝分裂谱，而缺乏DNA结合（Zip1或CR缺失）或ATP酶活性（K94A点突变体）的突变体则不能。综上所述，我们的结果表明Zip1和CR基序对于Kif4A的染色质结合及其有丝分裂功能都很重要。
