Studies on Microtubule Binding Proteins

描述(申请人提供)：细胞数量通过一分为二的方式增加。每个子细胞接收母细胞的一半内容和染色体的一个相同副本--这是遗传指令。在准备分裂的过程中，染色体对被收集在纺锤形的微管支架上。然后将这些对分离到主轴的两极。随后，两极进一步分开，带走了染色体，细胞膜收缩到纺锤体中面，将细胞挤压成两个子体，每个子体都有遗传物质的精确副本和原始细胞质的一半。这一描述是一个非常复杂和严格监管的过程的极大简化版本。微管是中心角色；它们定义了基本的纺锤体结构，它们是在不同阶段引导染色体到达目的地的轨道，它们是分子马达在细胞质分裂之前用来推动纺锤体极分离的底物。这一过程对健康和患病的细胞都是至关重要的。由于癌细胞分裂失控，纺锤体是抗癌药物的常见靶点。这项拟议的工作是一系列结构测定，旨在可视化至关重要的蛋白质和大分子复合体如何在微管的活动中心相互作用。感兴趣的区域是微管的正端和负端。在这里，协调的微管组装和拆解导致染色体收集，然后是染色体对的分离。特别令人感兴趣的是负责染色体附着到拆解微管正端的蛋白质，与正端结合和跟踪的蛋白质，以及覆盖和保护负端的蛋白质。另一个感兴趣的区域是纺锤体中心的区域，在那里来自相反两极的微管重叠。在这里，交联蛋白和马达决定和调节纺锤体的长度。结构测定将通过低温电子显微镜和图像分析进行。我们获得的结构结果将为从机制上理解纺锤体微管在细胞分裂过程中发生的一些最重要的事件提供基础。

DESCRIPTION (provided by applicant): Cells increase in number by dividing in two. Each daughter cell receives half the contents of the mother cell and an identical copy of the chromosomes - the genetic instructions. During preparation for division, the chromosome pairs are collected on a spindle shaped microtubule scaffold. The pairs are then separated to the two poles of the spindle. Subsequently the poles move further apart, taking the chromosomes with them and the cell membrane constricts into the spindle midplane, pinching the cell into two daughters each with an exact copy of the genetic material and half of the cytoplasm of the original. This description is a greatly simplified version of a very complicated and tightly regulated process. The microtubules are the central players; they define the basic spindle architecture, they are the tracks that guide chromosomes to their destinations at the various stages and they are the substrates that molecular motors use to push the spindle poles apart before the cytoplasm is divided. The process is of fundamental importance for both healthy and diseased cells. As cancer cells are dividing uncontrollably, the spindle is a common target for anti-cancer drugs. The proposed work is a series of structure determinations aimed at visualizing how critically important proteins and macromolecular complexes interact at foci of activity on the microtubules. The regions of interest are the plus and minus ends of microtubules. Here coordinated microtubule assembly and disassembly result in chromosome collection followed by separation of the chromosome pairs. Of particular interest are proteins responsible for chromosome attachment to disassembling microtubule plus ends, proteins that bind and track with the plus ends and a protein that caps and protects minus ends. The other region of interest is the zone in the center of the spindle where microtubules from opposite poles overlap. Here crosslinking proteins and motors determine and regulate spindle length. The structure determinations will be carried out by cryo-electron microscopy and image analysis. The structural results we obtain will provide the basis for a mechanistic understanding of some of the most important events taking place on spindle microtubules during cell division.