Höger T H, Zatloukal K, Waizenegger I, Krohne G
Division of Membrane Biology and Biochemistry, Institute of Cell and Tumor Biology, German Cancer Research Center, Heidelberg.
Chromosoma. 1990 Oct;99(6):379-90. doi: 10.1007/BF01726689.
Previous analyses of the nuclear lamina of mammalian cells have revealed three major protein components (lamins A, B and C) that have been identified by protein sequence homology as members of the intermediate filament (IF) protein family. It has been claimed that mammalian cells contain either all three lamins or lamin B alone. Using monoclonal antibodies specific for B-type lamins and cDNA cloning we identified a second major mammalian B-type lamin (murine lamin B2), thus showing that lamin composition in mammals is more complex than previously thought. Lamin B2 is coexpressed with lamin B1 (formerly termed lamin B) in all somatic cells and mammalian species that we analysed, including a variety of cells currently believed to contain only a single lamin. This suggests that two B-type lamins are necessary to form a functional lamina in mammalian somatic cells. By cDNA cloning we found that Xenopus laevis lamin LII is the amphibian homolog of mammalian lamin B2. Lamin expression during embryogenesis of amphibians and mammals shows striking similarities. The first lamins expressed in the early embryo are the two B-type lamins, while A-type lamins are only detected much later in development. These findings indicate that the genomic differentiation into two B-type lamins occurred early in vertebrate evolution and has been maintained in both their primary structure and pattern of expression.
先前对哺乳动物细胞核纤层的分析揭示了三种主要蛋白质成分（核纤层蛋白A、B和C），通过蛋白质序列同源性鉴定，它们是中间丝（IF）蛋白家族的成员。有人声称哺乳动物细胞要么含有所有三种核纤层蛋白，要么仅含有核纤层蛋白B。利用针对B型核纤层蛋白的单克隆抗体和cDNA克隆，我们鉴定出了第二种主要的哺乳动物B型核纤层蛋白（鼠核纤层蛋白B2），从而表明哺乳动物中的核纤层蛋白组成比之前认为的更为复杂。在我们分析的所有体细胞和哺乳动物物种中，包括目前认为只含有一种核纤层蛋白的各种细胞，核纤层蛋白B2与核纤层蛋白B1（以前称为核纤层蛋白B）共同表达。这表明在哺乳动物体细胞中，两种B型核纤层蛋白对于形成功能性核纤层是必需的。通过cDNA克隆，我们发现非洲爪蟾核纤层蛋白LII是哺乳动物核纤层蛋白B2的两栖类同源物。两栖动物和哺乳动物胚胎发育过程中的核纤层蛋白表达显示出惊人的相似性。早期胚胎中最早表达的核纤层蛋白是两种B型核纤层蛋白，而A型核纤层蛋白直到发育后期才被检测到。这些发现表明，在脊椎动物进化早期就发生了基因组分化形成两种B型核纤层蛋白的过程，并且在它们的一级结构和表达方式上都得以保留。
