Dagenais A, Bibor-Hardy V, Laliberté J F, Royal A, Simard R
Exp Cell Res. 1985 Dec;161(2):269-76. doi: 10.1016/0014-4827(85)90084-9.
Lamins are structural proteins found in the fibrous lamina underlining the nuclear envelope. In vitro translation of polyadenylated RNA or polysomes followed by immunoprecipitation with a serum raised against BHK nuclear matrix proteins showed that lamin A (72 kD) is synthesized as a high molecular weight precursor (74 kD) (Laliberté et al., J Cell Biol 98 (1984) 980) [23]. We have thus investigated the presence in BHK cells of this putative precursor by in vivo labelling with [35S]methionine and immunoprecipitation of lamin proteins. Short labelling times, ranging from 5 to 60 min reveal the presence of the 74 kD protein. Pulse-chase experiments indicate that the half-life of the precursor is about 60 min. On two-dimensional gel, the 74 kD protein is resolved in a cluster of isovariants between pH 7.4 and 6.6, which are generally slightly more alkaline than their counterparts in lamin A. These results indicate that lamin A is synthesized as a precursor of 74 kD; the long half-life further suggests that pre-lamin A might accumulate in some sort of cellular pool before undergoing post-transcriptional modification(s) to give the mature form of lamin A.
核纤层蛋白是存在于核膜下方纤维状核层中的结构蛋白。对聚腺苷酸化RNA或多核糖体进行体外翻译，然后用针对BHK核基质蛋白产生的血清进行免疫沉淀，结果表明核纤层蛋白A（72kD）是以高分子量前体（74kD）的形式合成的（拉利伯特等人，《细胞生物学杂志》98(1984)980）[23]。因此，我们通过用[35S]甲硫氨酸进行体内标记和对核纤层蛋白进行免疫沉淀，研究了BHK细胞中这种假定前体的存在情况。短时间标记（5至60分钟）显示存在74kD的蛋白。脉冲追踪实验表明前体的半衰期约为60分钟。在二维凝胶上，74kD的蛋白在pH 7.4至6.6之间的一组同变体中分离，这些同变体通常比核纤层蛋白A中的对应物略偏碱性。这些结果表明核纤层蛋白A是以74kD的前体形式合成的；较长的半衰期进一步表明前核纤层蛋白A可能在经历转录后修饰以产生成熟形式的核纤层蛋白A之前，在某种细胞池中积累。
