Modification of nuclear lamin proteins by a mevalonic acid derivative occurs in reticulocyte lysates and requires the cysteine residue of the C‐terminal CXXM motif

• Published in: The EMBO journal Vol. 8; no. 13; pp. 4007 - 4013
• Main Authors: Vorburger, K., Kitten, G.T., Nigg, E.A.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 20.12.1989
• Subjects: Animals; Biological and medical sciences; Cell-Free System; Cells, Cultured; Chick Embryo; Cysteine; DNA - genetics; Fibroblasts - metabolism; Fundamental and applied biological sciences. Psychology; Lamin Type A; Lamin Type B; Lamins; Mevalonic Acid - metabolism; Molecular and cellular biology; Molecular genetics; Mutation; Nuclear Proteins - biosynthesis; Nuclear Proteins - genetics; Peptide Mapping; Protein Biosynthesis; Protein Processing, Post-Translational; Protein-Tyrosine Kinases - genetics; Proto-Oncogene Proteins - genetics; Proto-Oncogene Proteins p21(ras); Reticulocytes - metabolism; Skin - metabolism; Transcription, Genetic; Transcription. Transcription factor. Splicing. Rna processing; Cell culture; Molecular processing; In vitro translation; Radiolabelling; Gel electrophoresis; Site directed mutagenesis; Posttranslational modification; Proteins; C terminal-Sequence; Peptide map; Vertebrata; Immunoprecipitation reaction; Complementary DNA; Structure activity relation; Proteolysis; Chicken; Reticulocyte; Aves
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1002/j.1460-2075.1989.tb08583.x

The C‐terminus of nuclear lamins (CXXM) resembles a C‐terminal motif (the CAAX box) of fungal mating factors and ras‐related proteins. The CAAX box is subject to different types of post‐translational modifications, including proteolytic processing, isoprenylation and carboxyl methylation. By peptide mapping we show that both chicken lamins A and B2 are processed proteolytically in vivo. However, whereas the entire CXXM motif is cleaved from lamin A, at most three C‐terminal amino acids are removed from lamin B2. Following translation of cDNA‐derived RNAs in reticulocyte lysates, lamin proteins specifically incorporate a derivative of [14C]mevalonic acid (MV), i.e. the precursor of a putative isoprenoid modification. Remarkably, no MV is incorporated into lamin B2 translated from a mutant cDNA encoding alanine instead of cysteine in the C‐terminal CXXM motif. These results implicate this particular cysteine residue as the target for modification of lamin proteins by an isoprenoid MV derivative, and they indicate that isoprenylation is amenable to studies in cell‐free systems. Moreover, our observations suggest that C‐terminal processing of newly synthesized nuclear lamins is a multi‐step process highly reminiscent of the pathway elaborated recently for ras‐related proteins.