Detection in BHK cells of a precursor form for lamin A.
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.
D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000032:analysis; D006224:Cricetinae; D005347:Fibroblasts / Q000032:analysis*; D007668:Kidney; D034904:Lamin Type A; D034882:Lamins; D008647:Mesocricetus; D009698:Nucleoproteins / Q000032:analysis* / Q000096:biosynthesis; D011498:Protein Precursors / Q000032:analysis*; D011499:Protein Processing, Post-Translational
D034904:Lamin Type A; D034882:Lamins; D009698:Nucleoproteins; D011498:Protein Precursors