Cell cycle-dependent methyl esterification of lamin B.
Cell cycle-dependent methyl esterification of lamin B.
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核纤层蛋白 B 的细胞周期依赖性甲酯化。
DOI：
10.1016/s0021-9258(18)61348-1
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
D. Koshland
中科院分区：
文献类型：
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作者：
D. Chelsky;J. Olson;D. Koshland
该实验室先前的工作表明，在小鼠淋巴瘤细胞系中，大约有24种蛋白质被甲基酯化可逆修饰。在这里，我们分析了几种小鼠组织以及其他小鼠、仓鼠和人类细胞系，发现许多蛋白质甲酯普遍存在，而其他蛋白质甲酯则表现出明显的组织特异性。其中一种修饰蛋白通过细胞定位和免疫检测鉴定为层粘连蛋白B，这是一种核膜结构蛋白，在有丝分裂过程中发生解聚。甲基化的平均化学计量是每层蛋白B分子至少0.5个甲基，由放射性掺入确定。然而，通过免疫印迹，去甲基化似乎导致两个负电荷的增加，这表明每个分子产生两个羧基的两个中性甲酯的损失。通过比较有丝分裂细胞和间期细胞，发现层粘连蛋白B在有丝分裂中去甲基化，而大多数其他甲基酯化蛋白没有明显的细胞周期依赖性。除了与细胞周期相关外，研究还表明，在完整的小鼠脑组织中，层粘连蛋白B不吸收放射性甲酯，但如果细胞被裂解，则可以吸收放射性甲酯。等电聚焦后的免疫印迹分析表明，该蛋白在大脑中完全甲基化，表明完整脑组织中甲基的转换受到抑制。我们认为层粘连蛋白B的甲基化可能参与有丝分裂过程中核膜的拆卸和重组的控制。如果是这样的话，大脑中甲基转换的明显缺乏将与这些细胞无法分裂相一致。
Previous work from this laboratory has shown that approximately 24 proteins are reversibly modified by methyl esterification in a mouse lymphoma cell line. Here, we analyze several mouse tissues as well as other mouse, hamster, and human cell lines and find that many protein-methyl esters are ubiquitous while others show apparent tissue specificity. One of the modified proteins is identified by cellular localization and immunological detection as lamin B, a nuclear envelope structural protein which undergoes depolymerization during mitosis. The average stoichiometry of methylation is at least 0.5 methyl groups per lamin B molecule as determined by radioactive incorporation. By immunoblotting, however, demethylation appears to result in a gain of two negative charges suggesting the loss of two neutral methyl esters producing two carboxylic acid groups per molecule. By comparing mitotic and interphase cells, lamin B is found to be demethylated in mitosis while most other methyl esterified proteins show no appreciable cell cycle dependence. In addition to the correlation with cell cycle, it is shown that lamin B does not incorporate radioactive methyl esters in intact mouse brain tissue yet can do so if the cells are lysed. Analysis of lamin B charge by immunoblotting after isoelectric focusing indicates that this protein is fully methylated in brain suggesting that turnover of methyl groups in intact brain tissue is inhibited. We propose that methylation of lamin B may be involved in the control of disassembly and reassembly of the nuclear envelope during mitosis. If this were the case, the apparent lack of methyl group turnover in brain would be consistent with the inability of those cells to divide.