Fontijn R D, Goud B, Echard A, Jollivet F, van Marle J, Pannekoek H, Horrevoets A J
Department of Biochemistry, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
Mol Cell Biol. 2001 Apr;21(8):2944-55. doi: 10.1128/MCB.21.8.2944-2955.2001.
Several members of the kinesin superfamily are known to play a prominent role in the motor-driven transport processes that occur in mitotic cells. Here we describe a new mitotic human kinesin-like protein, RB6K (Rabkinesin 6), distantly related to MKLP-1. Expression of RB6K is regulated during the cell cycle at both the mRNA and protein level and, similar to cyclin B, shows a maximum during M phase. Isolation of the RB6K promoter allowed identification of a CDE-CHR element and promoter activity was shown to be maximal during M phase. Immunofluorescence microscopy using antibodies raised against RB6K showed a weak signal in interphase Golgi but a 10-fold higher signal in prophase nuclei. During M phase, the newly synthesized RB6K does not colocalise with Rab6. In later stages of mitosis RB6K localized to the spindle midzone and appeared on the midbodies during cytokinesis. The functional significance of this localization during M phase was revealed by antibody microinjection studies which resulted exclusively in binucleate cells, showing a complete failure of cytokinesis. These results substantiate a crucial role for RB6K in late anaphase B and/or cytokinesis, clearly distinct from the role of MKLP-1.
已知驱动蛋白超家族的几个成员在有丝分裂细胞中发生的马达驱动运输过程中发挥着重要作用。在此，我们描述了一种新的有丝分裂人类驱动蛋白样蛋白RB6K（Rabkinesin 6），它与MKLP-1的关系较远。RB6K的表达在细胞周期的mRNA和蛋白质水平上均受到调控，并且与细胞周期蛋白B相似，在M期达到最大值。RB6K启动子的分离使得能够鉴定出一个CDE-CHR元件，并且已证明启动子活性在M期最大。使用针对RB6K产生的抗体进行免疫荧光显微镜观察显示，间期高尔基体中有微弱信号，但前期细胞核中的信号高10倍。在M期，新合成的RB6K不与Rab6共定位。在有丝分裂后期，RB6K定位于纺锤体中间区，并在胞质分裂期间出现在中体上。抗体显微注射研究揭示了这种在M期定位的功能意义，该研究仅产生双核细胞，表明胞质分裂完全失败。这些结果证实了RB6K在后期B和/或胞质分裂中起关键作用，这与MKLP-1的作用明显不同。
