中文摘要：

Nucleostemin（Ns）作为核仁蛋白，在神经干细胞、胚胎干细胞以及某些肿瘤细胞中均高表达，在多种肿瘤细胞增殖和凋亡调控中具有重要作用．本文通过瞬时转染NSsiRNA降低NS的表达，以探究NS对HepG2细胞增殖和凋亡的影响．结果显示，下调NS表达使HepG2细胞增殖加快，G，期细胞减少，S期及G：／M期细胞增加，凋亡减少．激光共聚焦实验表明，NS与s期激酶相关蛋白2（S-phase kinase—associated protein2，Skp2）在HepG2细胞中存在共定位现象；Co—IP实验证明，NS与Skp2能相互作用；Ns下调后，Skp2出核仁的数量增加，p27和p53表达降低．总之，下调NS可促进HepG2细胞中Skp2从核仁选出，p27降解增强，同时p53表达下降，或由此促进HepG2细胞增殖，抑制其凋亡．

英文摘要：

Nucleostemin （NS） is a high expression nucleolin in many stem cells and certain tumors. NS plays important role in the regulation of cell proliferation and apoptosis, especially in cancer cells. To investigate the impact of NS knock-down of its cellular response, we transiently transfected the NS siRNA in HepG2 cells. We found that NS down-regulation accelerated cell proliferation, attenusted the G1 phase of cell cycle and increased the S and G2/M phases significantly. The apoptotic percentage of ceils was decreased as compared to the control group. The results of confocal colocalization suggested the interaction between NS and S-phase kinase-associated protein 2 （Skp2）, which was verified by Co-IP experiments. The down-regulation of NS expression enhanced the mobilization of Skp2 from nucleolus indicated its role to maintain Skp2 nucleolar retention in HepG2 cells. The suppression of NS might influence Skp2 for its ubiquitination and degradation, thus to influence the downstream tumor suppressor molecules like p27 and p53 to repress cell proliferation.