类Cyclin A蛋白在多头绒泡菌细胞周期中的定位研究

采用免疫电镜技术对多头绒泡菌(Physarum polycephalum)是否含有类CyclinA蛋白以及该蛋白在有丝分裂周期各时相的定位进行了研究；并以抗CyclinA抗体封闭细胞内源类CyclinA蛋白的方法，探讨类CyclinA蛋白在多头绒泡菌细胞周期中的作用。免疫电镜结果表明，经抗CyclinA抗体标记的实验组细胞中的金颗粒密度明显高于对照组，说明多头绒泡菌细胞中含有类CyclinA蛋白。实验组样品中，细胞核的金颗粒密度很高，而细胞质的金颗粒密度与对照组的相仿，说明多头绒泡菌细胞中的类CyclinA蛋白是核蛋白。细胞核的金颗粒密度在S期最高，G2期的次之，早中期时明显降低，中期和中期以后与对照组的相近。这种金颗粒密度的变化反映了类CyclinA蛋白在细胞周期中的含量变化。以抗CyclinA抗体分别处理S期和G2期的多头绒泡菌细胞，处理后的细胞分别停滞在原来的时相，细胞核形态变得不规则，核内有空洞现象。处于有丝分裂前期的多头绒泡菌细胞经抗CyclinA抗体处理后，细胞核出现畸变。抗体处理结果说明类CyclinA蛋白是参与多头绒泡菌细胞周期多个转换过程调控的种重要蛋白，主要在S期／G2期和G2期／M期的转换以及走出有丝分裂期的进程中发挥作用。

A Cyclin A-like Protein is Localized in the Cells of Physarum polycephalum and Functions in the Cell Cycle

The subcellular distribution of a Cyclin A-like protein in the cells of Physarum polycephalum and the function of the protein in the cell cycle were studied by immunoelectron microscope and anti-Cyclin A antibody blocking.After labeled with an anti-Cyclin A monoclonal antibody,the density of gold particles in the labeled specimens was much higher than that in the control,indicating that a Cyclin A-like protein existed in Physarum polycephalum.In the labeled specimen,the gold particles density of the nucleus was higher than that of cytoplasm,which was similar to that of the control,demonstrating that the Cyclin A-like protein was a nuclear protein.The gold particles densitiy of the nuclei varied during the cell cycle.The highest appeared in S phase and the lowest came in metaphase and ana-telophase,which was close to that in the control.From S phase to metaphase,the gold particle densities dropped down gradually.The changes in the gold particle density showed the changes in the content of the Cyclin A-like protein.After treated with the anti-Cyclin A antibody in S phase and G2 phase respectively,the nuclei of Physarum polycephalum were arrested in the phases and the morphology of these nuclei became irregular.When treated with the anti-Cyclin A antibody in prophase,the nuclei appeared abnormal.These results suggested that the Cyclin A-like protein is important in cell cycle regulation of Physarum polycephalum,essentially in S/G2 and G2/M changes.