title: Suppression of synthesis of pro-alpha 1(I) and production of altered pro-alpha 2(I) procollagen subunits in 4-nitroquinoline-1-oxide-transformed fibroblasts.
abstract: The collagen phenotype of a 4-nitroquinoline-1-oxide-transformed line of Syrian hamster embryo fibroblasts, NQT-SHE, was markedly altered from that of normal Syrian hamster embryo cells, which synthesized mainly type I procollagen [pro-alpha 1(I)]2 pro-alpha 2(I). Total collagen synthesis in the transformant was reduced to about 30% of the control level primarily because synthesis of the pro-alpha 1(I) subunit was completely suppressed. The major collagenous products synthesized consisted of two polypeptides, designated as N-33 and N-50, which could be completely separated by precipitation with ammonium sulfate at 33 and 50% saturation, respectively. N-33 migrated similarly to pro-alpha 2(I) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and N-50 migrated slightly more slowly. The collagenous regions of these chains were more sensitive to protease than the analogous region of procollagen I, but alpha-chains could be obtained by digestion for 2 h at 4 degrees C with high ratios of protein:pepsin. Staphylococcus V8 protease and cyanogen bromide peptide maps of N-33 alpha and N-50 alpha chains indicated that the chains were homologous with, but different than, alpha 2(I) chains and that they differed from each other. Considering their similarity to pro-alpha 2(I), it was surprising to find that the N-collagens were secreted to the same extent as was type I procollagen from Syrian hamster embryo cells and that there were no disulfide bonds between N-collagen chains. Intrachain disulfides were present. One possible explanation for the unusual collagen phenotype of NQT-SHE cells is that transformation induced one or more mutations in the pro-alpha 2(I) structural gene while suppression of synthesis of the pro-alpha 1(I) subunit may be due to a mutation in the regulatory region of its gene or in a general regulatory gene.
mesh_terms: D015112:4-Nitroquinoline-1-oxide / Q000494:pharmacology*; D000818:Animals; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis; D006224:Cricetinae; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D007621:Karyotyping; D046911:Macromolecular Substances; D008647:Mesocricetus; D009600:Nitroquinolines / Q000494:pharmacology*; D010446:Peptide Fragments / Q000032:analysis; D011347:Procollagen / Q000096:biosynthesis* / Q000302:isolation & purification
chemical_list: D046911:Macromolecular Substances; D009600:Nitroquinolines; D010446:Peptide Fragments; D011347:Procollagen; D015112:4-Nitroquinoline-1-oxide; D003094:Collagen