Biosynthesis of the v-sis gene product: signal sequence cleavage, glycosylation, and proteolytic processing.
The v-sis oncogene and its cellular homolog c-sis encode chain B of platelet-derived growth factor. Cells transformed by v-sis produce a platelet-derived growth factor-related molecule which is able to stimulate the platelet-derived growth factor receptor in an autocrine fashion. Site-directed mutagenesis was used to construct several mutations which substitute charged residues for hydrophobic residues in the proposed signal sequence of the v-sis gene product. Two of these mutations resulted in the synthesis of altered v-sis gene products with an unexpected nuclear location and a loss of biological activity. We also report here the intracellular localization of the v-sis gene product to the endoplasmic reticulum-Golgi compartment, where signal sequence cleavage and N-linked glycosylation occur. The v-sis gene product contains no transmembrane regions, as it is completely protected within isolated microsomes from trypsin proteolysis. Site-directed mutagenesis was also used to alter a proposed proteolytic processing site in the v-sis gene product. This mutant v-sis gene, which encodes Asn-Ser in place of Lys-Arg at residues 110 to 111, was found to retain full biological activity.
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D005455:Fluorescent Antibody Technique; D005796:Genes; D051379:Mice; D008815:Mice, Inbred Strains; D010982:Platelet-Derived Growth Factor / Q000096:biosynthesis / Q000235:genetics*; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals / Q000378:metabolism*
D010982:Platelet-Derived Growth Factor; D021382:Protein Sorting Signals