Identification of distinct messenger RNAs for nuclear lamin C and a putative precursor of nuclear lamin A.

Open Access
Publisher Website
Google Scholar
Abstract
The lamins are the major components of the nuclear matrix and are known as lamins A, B and C with MW 72,000, 68,000 and 62,000 when analyzed by SDS PAGE [sodium dodecyl sulfate polyacrylamide gel electrophoresis]. These 3 polypeptides are very similar, as determined by polypeptide mapping and immunological reactivity. Lamins A and C are so homologous that a precursor-product relationship has been proposed. Using an antiserum against nuclear matrix proteins that specifically immunoprecipitates the 3 lamins, their synthesis in the rabbit reticulocytes lysate was examined. Four bands of MW 62,000, 68,000, 70,000 and 74,000 were specifically immunoprecipitated when polysomes or polyadenylated RNA were translated in vitro. By 2-dimensional gel electrophoresis, the 68,000- and the 62,000-MW proteins were identified as lamins B and C, respectively, and the 74,000-MW polypeptide had properties of a precursor of lamin A. The mRNA of lamin C and of the putative precursor of lamin A were completely separated by gel electrophoresis under denaturing conditions, and their respective sizes were determined. Evidently, lamin A is not a precursor of lamin C.