Das Arunika, Cesario Jeffry, Hinman Anna Maria, Jang Janet K, McKim Kim S
Waksman Institute, Rutgers, the State University of New Jersey, NJ-08854
Waksman Institute, Rutgers, the State University of New Jersey, NJ-08854.
G3 (Bethesda). 2018 May 4;8(5):1555-1569. doi: 10.1534/g3.117.300571.
Bipolar spindle assembly occurs in the absence of centrosomes in the oocytes of most organisms. In the absence of centrosomes in oocytes, we have proposed that the kinesin 6 Subito, a MKLP-2 homolog, is required for establishing spindle bipolarity and chromosome biorientation by assembling a robust central spindle during prometaphase I. Although the functions of the conserved motor domains of kinesins is well studied, less is known about the contribution of the poorly conserved N- and C- terminal domains to motor function. In this study, we have investigated the contribution of these domains to kinesin 6 functions in meiosis and early embryonic development. We found that the N-terminal domain has antagonistic elements that regulate localization of the motor to microtubules. Other parts of the N- and C-terminal domains are not required for microtubule localization but are required for motor function. Some of these elements of Subito are more important for either mitosis or meiosis, as revealed by separation-of-function mutants. One of the functions for both the N- and C-terminals domains is to restrict the CPC to the central spindle in a ring around the chromosomes. We also provide evidence that CDK1 phosphorylation of Subito regulates its activity associated with homolog bi-orientation. These results suggest the N- and C-terminal domains of Subito, while not required for localization to the central spindle microtubules, have important roles regulating Subito, by interacting with other spindle proteins and promoting activities such as bipolar spindle formation and homologous chromosome bi-orientation during meiosis.
在大多数生物体的卵母细胞中，双极纺锤体的组装是在没有中心体的情况下发生的。在卵母细胞缺乏中心体的情况下，我们提出驱动蛋白6 Subito（一种MKLP - 2同源物）对于在减数分裂前期I通过组装强大的中央纺锤体来建立纺锤体双极性和染色体双取向是必需的。尽管对驱动蛋白保守的运动结构域的功能进行了充分研究，但对于保守性较差的N端和C端结构域对运动功能的贡献了解较少。在本研究中，我们研究了这些结构域对驱动蛋白6在减数分裂和早期胚胎发育中的功能的贡献。我们发现N端结构域具有调节运动蛋白定位于微管的拮抗元件。N端和C端结构域的其他部分对于微管定位不是必需的，但对于运动功能是必需的。功能分离突变体表明，Subito的一些元件对有丝分裂或减数分裂更为重要。N端和C端结构域的功能之一是将染色体乘客复合体（CPC）限制在围绕染色体的中央纺锤体周围呈环状。我们还提供证据表明，Subito的CDK1磷酸化调节其与同源物双取向相关的活性。这些结果表明，Subito的N端和C端结构域虽然不是定位于中央纺锤体微管所必需的，但通过与其他纺锤体蛋白相互作用并促进减数分裂过程中的双极纺锤体形成和同源染色体双取向等活动，在调节Subito方面具有重要作用。
