Vorburger K, Lehner C F, Kitten G T, Eppenberger H M, Nigg E A
Institute for Cell Biology, ETH-Hönggerberg, Zurich, Switzerland.
J Mol Biol. 1989 Aug 5;208(3):405-15. doi: 10.1016/0022-2836(89)90505-6.
The chicken nuclear lamina is composed of at least three proteins called lamins A, B1 and B2. In addition, putative precursors are transiently expressed during in vivo synthesis of lamins A and B2. Here we report the complete sequence of lamin B2 as it is deduced from a cloned cDNA. Comparison of lamin B2 with lamins A and B1 in the accompanying paper provides definitive proof for the existence of two structurally distinct chicken B-type lamins. Furthermore, we show that in vitro translation of transcripts derived from lamin A and lamin B2 cDNAs yielded polypeptides that were indistinguishable, by two-dimensional gel electrophoresis, from the putative in vivo precursors of lamins A and B2 respectively. However, whereas the lamin A precursor was stable, the translation product of the lamin B2 transcript was processed in the reticulocyte lysate to a polypeptide comigrating on two-dimensional gels with authentic mature lamin B2. This processing event could be inhibited by chelators of divalent cations, i.e. o-phenanthroline and EDTA. Our results indicate that the transiently expressed variant of lamin B2 represent a bonafide precursor, and that two distinct activities are involved in processing of newly synthesized lamins A and B2. Lamin precursors processing is discussed in relation to characteristic differences in the interactions of A and B-type lamins with the nuclear membrane.
鸡的核纤层由至少三种名为核纤层蛋白A、B1和B2的蛋白质组成。此外，在核纤层蛋白A和B2的体内合成过程中会短暂表达假定的前体。在此，我们报告从克隆的cDNA推导得出的核纤层蛋白B2的完整序列。随附论文中核纤层蛋白B2与核纤层蛋白A和B1的比较为两种结构不同的鸡B型核纤层蛋白的存在提供了确凿证据。此外，我们表明，源自核纤层蛋白A和核纤层蛋白B2 cDNA的转录本的体外翻译分别产生了通过二维凝胶电泳与核纤层蛋白A和B2的假定体内前体无法区分的多肽。然而，核纤层蛋白A前体是稳定的，而核纤层蛋白B2转录本的翻译产物在网织红细胞裂解物中被加工成在二维凝胶上与真正的成熟核纤层蛋白B2共迁移的多肽。这种加工事件可被二价阳离子螯合剂即邻菲罗啉和乙二胺四乙酸抑制。我们的结果表明，核纤层蛋白B2的短暂表达变体代表真正的前体，并且新合成的核纤层蛋白A和B2的加工涉及两种不同的活性。结合A和B型核纤层蛋白与核膜相互作用的特征差异讨论了核纤层蛋白前体的加工。
