Li Y P, Busch R K, Valdez B C, Busch H
Department of Pharmacology, Baylor College of Medicine, Houston, TX 77030, USA.
Eur J Biochem. 1996 Apr 1;237(1):153-8. doi: 10.1111/j.1432-1033.1996.0153n.x.
The human protein C23 (nucleolin) is a major nucleolar protein. Its interactions with other proteins were studied with the two-hybrid system which identified nucleolar protein B23 (nucleophosmin) as being associated with C23. Both proteins were co-immunoprecipitated from HeLa cell nuclear extract by either monoclonal anti-C23 or monoclonal anti-B23. Binding studies utilizing deletion mutants indicated that the binding of C23 and B23 involves specific motifs. In addition to an approximately 46-amino-acid-binding domain in B23 (amino acids 194-239), amino acids 540-628 of C23 were required for binding; this region of C23 is required for the nucleolar localization. In addition, nucleolar protein p120 was also found to be co-immunoprecipitated with B23. A fragment of p120 containing a functional nucleolar localization signal bound to the truncated binding domain of B23, as did C23. These results suggest that the interaction of C23 and B23 may represent a nucleolar-targeting mechanism in which B23 acts as a nucleolar-localization signal-binding protein.
人类蛋白质C23（核仁素）是一种主要的核仁蛋白。利用双杂交系统研究了它与其他蛋白质的相互作用，该系统确定核仁蛋白B23（核磷蛋白）与C23相关。单克隆抗C23或单克隆抗B23均可从HeLa细胞核提取物中共免疫沉淀这两种蛋白质。利用缺失突变体进行的结合研究表明，C23和B23的结合涉及特定基序。除了B23中一个约46个氨基酸的结合结构域（氨基酸194 - 239）外，C23的氨基酸540 - 628对于结合也是必需的；C23的这一区域是核仁定位所必需的。此外，还发现核仁蛋白p120也与B23共免疫沉淀。含有功能性核仁定位信号的p120片段与B23的截短结合结构域结合，C23也是如此。这些结果表明，C23和B23的相互作用可能代表一种核仁靶向机制，其中B23作为核仁定位信号结合蛋白发挥作用。
