Molecular mechanism of cytokinesis in animal cells

1. 我们从分裂酵母中发现了一个新的rho基因，命名为rho5^+。rho1基因的干扰物不能生长，表明rho1^+是必需基因。我们通过免疫荧光显微镜和GFP-Rhol融合蛋白在分裂酵母细胞中的表达，将Rho1定位在间期生长尖端和细胞质分裂期间的隔膜上。Rhol基因的过度表达导致细胞形态异常、肌动蛋白斑块脱位和细胞壁增厚。Rho2过表达致死性，细胞形态异常，细胞壁异常厚。rho3基因的破坏导致细胞形态异常和分裂异常。rho4基因的破坏导致细胞极性丧失和异常分裂。通过F-actin亲和层析，从海胆卵中发现了新的F-actin结合蛋白。其中60K蛋白鉴定为冠蛋白，150K蛋白鉴定为肌凝蛋白6。免疫荧光显微镜显示，这些蛋白质和ARP3，我们在去年鉴定，存在于卵裂沟皮层。我们从裂变酵母中克隆了ARP3基因并破坏了它。末端表型显示肌动蛋白斑块脱位。ABP40是一种集中在海胆卵卵裂沟中的蛋白质，被证明具有切断f -actin的活性。

1. Cleavage signaling pathwayWe found a new rho gene from the fission yeast and named it rho5^+.Disruptant of rho1 gene could not grow indicating that rho1^+ is an essential gene. We localized Rho1 by both immunofluorescence microscopy and expression of GFP-Rhol fusion protein in the fission yeast cell to growing tips during interphase and to septum during cytokinesis. Overexperssion of Rhol induced aberrant morphology, delocalization of actin patches, and thickening of cell wall. Overexperssion of Rho2 was lethal, cell morphology was aberrant and cell wall was abnormally thick. Disruption of rho3 gene induced aberrant morphology of the cell and abnormal division. Disruption of rho4 gene induced loss of cell polarity and abnormal division.2. Structure and foumation of the contractile ringWe found novel F-actin-binding proteins from sea urchin eggs by F-actin affinity chromatography. Among them, 60K protein was indentified as coronin and 150K protein was identified as myosin 6. Immunofluorescence microscopy showed that these proteins and ARP3, which we indentified in the last year, are present in the cleavage furrow cortex. We gene-cloned ARP3 from fission yeast and disrupted it. The terminal phenotype showed that actin patches were delocalized. ABP40, a protein which is concentrated in the cleavage furrow of the sea urchin egg, was demonstrated to have an F-actin-severing activity.