THE SELF-CLEAVING ACTIVITY OF NUCLEOLIN DETERMINES ITS MOLECULAR-DYNAMICS IN RELATION TO CELL-PROLIFERATION
THE SELF-CLEAVING ACTIVITY OF NUCLEOLIN DETERMINES ITS MOLECULAR-DYNAMICS IN RELATION TO CELL-PROLIFERATION
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DOI：
10.1006/excr.1993.1221
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发表时间：
1993-09-01
影响因子：
3.7
通讯作者：
YEH, NH
中科院分区：
文献类型：
--
作者：
FANG, SH;YEH, NH
核仁蛋白 (105 kDa) 是指数生长细胞中最丰富的核仁磷蛋白。我们已经证明核仁素具有自降解的内在蛋白酶活性。当细胞进入增殖阶段时，这种自裂解活性显着降低，导致核仁素分子显着稳定。源自部分核仁素 cDNA 克隆的融合蛋白，编码 C 端三分之二的核仁素，保持了与从非增殖细胞纯化的核仁素相似的自裂解活性。因此酶结构域位于该区域内。带高负电荷的外源肽发挥抑制作用，表明酶活性可以被调节。从增殖细胞中分离的核仁素的裂解动力学显然与浓度无关，表明分裂阶段细胞中核仁素的自蛋白水解反应是分子内事件。裂解片段较多，聚集在四个主要位点，表观分子量约为100、70、60、50 kDa。这些结果意味着核仁素分子具有作为切割位点的重复基序。由于来自非增殖和增殖细胞的核仁素体外自切割产物的详细电泳模式，包括位置和强度，并不完全相同，因此建议根据细胞阶段优先使用特定的切割位点。增殖细胞中核仁素的翻译后修饰可能会导致这些变异。
Nucleolin (105 kDa) is the most abundant nucleolar phosphoprotein in exponentially growing cells. We have demonstrated that nucleolin has an intrinsic protease activity for autodegradation. This self-cleaving activity is markedly decreased when cells enter the proliferative stage, resulting in significant stabilization of the nucleolin molecule. The fusion protein derived from a partial nucleolin cDNA clone, which encodes the C-terminal two-thirds of nucleolin, maintained the self-cleaving activity similar to that of the nucleolin purified from nonproliferating cells. The enzymatic domain is therefore located within this region. An exogenous peptide, highly negatively charged, exerted an inhibitory effect, indicating that the enzymatic activity can be regulated. The cleavage kinetics of nucleolin isolated from proliferating cells was apparently concentration independent, suggesting that the autoproteolytic reaction of nucleolin in cells at dividing stage is an intramolecular event. There were many cleavage fragments, which were clustered at four major sites, with apparent molecular weights of about 100, 70, 60, and 50 kDa. These results imply that the nucleolin molecule has repeated motifs that serve as the cleavage sites. Since the detailed electrophoresis patterns, including location and intensity, of thein vitroself-cleaved products of nucleolin derived from nonproliferating and proliferating cells were not quite the same, preferential usage of the particular cutting sites according to cell stage was suggested. It is possible that post-translational modification of nucleolin in proliferating cells may cause these variations.