Cell Cycle Regulation of Microtubule Assembly

这项研究的目的是确定在发育中的海胆胚胎的间期到有丝分裂转变过程中，参与微管组装调节的大分子。未受精的海胆卵停留在第一个有丝分裂周期的G1，尽管有大量的微管蛋白亚基，但几乎没有组装的微管。受精后，第一卵裂有丝分裂器的微管同步组装。因此，发育中的海胆胚胎可以被视为研究微管组装调控的诱导型模型系统。最近发现，间期受阻的卵细胞含有两种新型的微管组装抑制物--负端抑制物和pH依赖的正端抑制物。这项拟议的研究的目标是分离和表征细胞周期中的这些独特因素。对海胆卵、文蛤卵母细胞、小鼠B16黑色素瘤细胞、鱿鱼视叶和哺乳动物脑组织等多种来源的初步实验表明，这些负调控因子可能存在于所有真核细胞中，特别是在细胞周期中细胞质微管以受控方式快速组装和拆解的情况下。有丝分裂微管阵列和间期微管阵列在细胞周期中的相互转换是细胞形态发生的一个基本问题。这一过程对细胞分裂以及神经元生长和可塑性等发育过程都具有明显的重要性。这些研究有望增加我们对微管组装在活细胞中被调控的基本机制的理解。

The intent of this study is to identify the macromolecules involved in the regulation of microtubule assembly during the interphase-to- mitosis transition in developing sea urchin embryos. Unfertilized sea urchin eggs are arrested at G1 of the first mitotic cycle and have few, if any assembled microtubules despite a large pool of tubulin subunits. Following fertilization microtubules of the first cleavage mitotic apparatus are synchronously assembled. Therefore the developing sea urchin embryo can be viewed as an inducible model system for studying the regulation of microtubule assembly. It has been recently discovered that interphase-arrested egg cells contain two novel inhibitors of microtubule assembly- a minus-end inhibitor and a pH-dependent plus-end inhibitor. The goal of the proposed research is to isolate and characterize these unique factors during the cell cycle. Preliminary experiments with such diverse sources as sea urchin eggs, surf clam oocytes, mouse B16 cultured melanoma cells, squid optic lobe and mammalian brain tissue suggest that these negative control factors may exist in all eukaryotic cells, particularly where cytoplasmic microtubules are rapidly assembled and disassembled in a controlled manner during the cell cycle. The interconversion of mitotic and interphase microtubule arrays during the cell cycle is a fundamental problem of cellular morphogenesis. The process is of obvious importance for cell division but also for developmental processes such as neuronal growth and plasticity. These studies are expected to increase our understanding of fundamental mechanisms whereby microtubule assembly is regulated in the living cell.