Leno G H, Mills A D, Philpott A, Laskey R A
Department of Biochemistry, University of Mississippi Medical Center, Jackson, 39216, USA.
J Biol Chem. 1996 Mar 29;271(13):7253-6. doi: 10.1074/jbc.271.13.7253.
Previous studies showed that the nuclear phosphoprotein nucleoplasmin performs the first stage of chromatin decondensation of Xenopus sperm at fertilization. It binds and removes sperm basic proteins replacing them with histones. We now show that this activity depends upon the massive hyperphosphorylation of nucleoplasmin that occurs when oocytes mature into eggs. Egg extracts or purified hyperphosphorylated egg nucleoplasmin decondense sperm chromatin and remove sperm basic proteins much faster than oocyte extracts or hypophosphorylated oocyte nucleoplasmin. Furthermore, dephosphorylation of egg nucleoplasmin slows sperm decondensation and prevents basic protein removal from sperm chromatin. We conclude that hyperphosphorylation of nucleoplasmin is used to modulate the rapid changes in chromatin structure that accompany early development in Xenopus.
先前的研究表明，核磷蛋白在受精时执行非洲爪蟾精子染色质解聚的第一阶段。它结合并去除精子碱性蛋白，并用组蛋白取而代之。我们现在表明，这种活性取决于卵母细胞成熟为卵子时发生的核磷蛋白大量超磷酸化。卵提取物或纯化的超磷酸化卵核磷蛋白使精子染色质解聚并去除精子碱性蛋白的速度比卵母细胞提取物或低磷酸化卵母细胞核磷蛋白快得多。此外，卵核磷蛋白的去磷酸化会减缓精子解聚，并阻止从精子染色质中去除碱性蛋白。我们得出结论，核磷蛋白的超磷酸化用于调节非洲爪蟾早期发育过程中伴随的染色质结构的快速变化。
