Limited proteolysis of rat liver nucleolin by endogenous proteases: effects of polyamines and histones.
Limited proteolysis of rat liver nucleolin by endogenous proteases: effects of polyamines and histones.
复制标题
内源性蛋白酶对大鼠肝核蛋白的有限蛋白水解：多胺和组蛋白的作用。
DOI：
10.1042/bj2890109
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
T. Hosoya
中科院分区：
文献类型：
--
作者：
T. Suzuki;N. Suzuki;T. Hosoya
核仁蛋白是一种主要的核仁磷蛋白，可能参与 rDNA 转录和核糖体生物合成。众所周知，这种蛋白质非常不稳定，会被内源蛋白酶切割成许多小肽。我们发现，当大鼠肝核仁悬浮液（Nu-1）或富含核仁素的提取物（Nu-2）在常规条件下孵育时，多胺和组蛋白与核仁素相互作用，导致其优先降解为60 kDa磷酸肽（p60）。根据肽图分析判断，肽p60被鉴定为含有核仁素分子N末端一半的肽。当 KCl 浓度高于 50 mM 时，精胺与纯化核仁素的结合会减少，而组蛋白（H1、H2B 和 H3）在 KCl 浓度高达 300 mM 的情况下能够与核仁素结合。 H1 和其他组蛋白之间的明显区别在于，H1 可以从 Nu-1 和 Nu-2 中的核仁素产生 p60，而只有当 Nu-2 用作核仁素来源时，H2B 和 H3 才刺激核仁素降解为 p60。讨论了 p60 形成和 rRNA 合成之间可能的关系，但其确切作用仍有待研究。
Nucleolin is a major nucleolar phosphoprotein and is presumably involved in rDNA transcription and ribosome biosynthesis. This protein is known to be very labile and to be cleaved by endogenous proteases into many small peptides. We found that, when rat liver nucleolar suspension (Nu-1) or nucleolin-rich extract (Nu-2) was incubated under conventional conditions, polyamines and histones interacted with the nucleolin to lead to its preferential degradation to 60 kDa phosphopeptide (p60). The peptide p60 was identified as a peptide containing the N-terminal half of the nucleolin molecule, as judged from peptide-map analysis. Whereas spermine binding to the purified nucleolin was decreased by KCl concentrations above 50 mM, histones (H1, H2B and H3) were able to bind to the nucleolin in the presence of up to 300 mM KCl. A distinct difference between H1 and other histones was found in that H1 could produce p60 from nucleolin in both Nu-1 and Nu-2, whereas H2B and H3 stimulated the degradation of nucleolin to p60 only when Nu-2 was used for the source of nucleolin. A possible relationship between p60 formation and rRNA synthesis is discussed, but its exact role remains to be studied.