Syrovatkina Viktoriya, Fu Chuanhai, Tran Phong T
Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
Curr Biol. 2013 Dec 2;23(23):2423-9. doi: 10.1016/j.cub.2013.10.023. Epub 2013 Nov 14.
Metaphase describes a phase of mitosis where chromosomes are attached and oriented on the bipolar spindle for subsequent segregation at anaphase. In diverse cell types, the metaphase spindle is maintained at characteristic constant length [1-3]. Metaphase spindle length is proposed to be regulated by a balance of pushing and pulling forces generated by distinct sets of spindle microtubules (MTs) and their interactions with motors and MT-associated proteins (MAPs). Spindle length is further proposed to be important for chromosome segregation fidelity, as cells with shorter- or longer-than-normal metaphase spindles, generated through deletion or inhibition of individual mitotic motors or MAPs, showed chromosome segregation defects. To test the force-balance model of spindle length control and its effect on chromosome segregation, we applied fast microfluidic temperature control with live-cell imaging to monitor the effect of deleting or switching off different combinations of antagonistic force contributors in the fission yeast metaphase spindle. We show that the spindle midzone proteins kinesin-5 cut7p and MT bundler ase1p contribute to outward-pushing forces and that the spindle kinetochore proteins kinesin-8 klp5/6p and dam1p contribute to inward-pulling forces. Removing these proteins individually led to aberrant metaphase spindle length and chromosome segregation defects. Removing these proteins in antagonistic combination rescued the defective spindle length and in some combinations also partially rescued chromosome segregation defects.
中期描述了有丝分裂的一个阶段，在此阶段染色体附着并排列在双极纺锤体上，以便在后期进行后续分离。在不同的细胞类型中，中期纺锤体保持在特征性的恒定长度[1-3]。中期纺锤体长度被认为是由不同组的纺锤体微管（MTs）产生的推拉力及其与马达蛋白和微管相关蛋白（MAPs）的相互作用之间的平衡来调节的。纺锤体长度对于染色体分离保真度也很重要，因为通过缺失或抑制单个有丝分裂马达蛋白或MAPs而产生的中期纺锤体比正常短或长的细胞表现出染色体分离缺陷。为了测试纺锤体长度控制的力平衡模型及其对染色体分离的影响，我们应用快速微流控温度控制结合活细胞成像来监测在裂殖酵母中期纺锤体中删除或关闭拮抗力量贡献者的不同组合的效果。我们发现纺锤体中间区蛋白驱动蛋白-5（cut7p）和微管束集蛋白（ase1p）有助于向外推的力，而纺锤体动粒蛋白驱动蛋白-8（klp5/6p）和dam1p有助于向内拉的力。单独去除这些蛋白会导致中期纺锤体长度异常和染色体分离缺陷。以拮抗组合去除这些蛋白可挽救有缺陷的纺锤体长度，并且在某些组合中还部分挽救了染色体分离缺陷。
