Furukawa K, Inagaki H, Hotta Y
Department of Biology, School of Science, Nagoya University, Japan.
Exp Cell Res. 1994 Jun;212(2):426-30. doi: 10.1006/excr.1994.1164.
The nuclear lamins are karyoskeletal proteins which have important functions, such as maintaining nuclear envelope integrity and organizing high order nuclear structure during mitosis in higher eukaryotes. In somatic mammalian cells, the A-type and B-type lamins, composed of lamins A and C and lamins B1 and B2, are major components of the nuclear lamina. However, A-type lamins have as yet not been identified in germ cells and undifferentiated embryonic cells. Here we report the cloning of a new 52-kDa A-type lamin from mouse pachytene spermatocytes, termed lamin C2 because of its similarities with lamin C. It has a sequence identical to that of lamin C except that the N-terminal segment, containing the head and the alpha-helical coil 1A domains, is replaced with a short non-alpha-helical stretch of amino acids. In mice, lamin C2 was found to be specifically expressed in germ cells. This specific expression and unique structure suggests a role for lamin C2 in determining the organization of nuclear and chromosomal structures during spermatogenesis.
核纤层蛋白是核骨架蛋白，具有重要功能，如在高等真核生物有丝分裂期间维持核膜完整性和组织高阶核结构。在哺乳动物体细胞中，由核纤层蛋白A和C以及核纤层蛋白B1和B2组成的A型和B型核纤层蛋白是核纤层的主要成分。然而，在生殖细胞和未分化的胚胎细胞中尚未鉴定出A型核纤层蛋白。在此，我们报道从小鼠粗线期精母细胞中克隆出一种新的52 kDa A型核纤层蛋白，因其与核纤层蛋白C相似而被称为核纤层蛋白C2。它的序列与核纤层蛋白C相同，只是包含头部和α-螺旋卷曲1A结构域的N端片段被一段短的非α-螺旋氨基酸序列所取代。在小鼠中，发现核纤层蛋白C2在生殖细胞中特异性表达。这种特异性表达和独特结构表明核纤层蛋白C2在精子发生过程中决定核和染色体结构的组织方面发挥作用。
