J. Biol. Chem., Vol. 263, Issue 12, 5555-5559, 04, 1988

Uncoupled expression of mRNAs for alpha 1(I) and alpha 2(I) procollagen chains in chemically transformed Syrian hamster fibroblasts

G Majmudar, E Schalk, J Bateman and B Peterkofsky
Laboratory of Biochemistry, National Cancer Institute, Bethesda, Maryland 20892.

Syrian hamster embryo fibroblasts transformed by 4-nitroquinoline-1- oxide (NQT-SHE cells) failed to synthesize the pro-alpha 1(I) subunit of type I procollagen but continued to synthesize altered forms of the other subunit, pro-alpha 2(I) (Peterkofsky, B., and Prather, W. (1986) J. Biol. Chem. 261, 16818-16826). This was unusual, since synthesis of the two subunits generally is coordinately regulated. Present experiments using cell-free translation and hybridization of RNA from normal and transformed Syrian hamster fibroblasts with labeled pro- alpha 1(I) DNA probes show that mRNA for pro-alpha 1(I) is absent from the transformant. In contrast, dot-blot and Southern blot hybridizations of cellular DNAs with pro-alpha 1(I) DNA probes demonstrated that the transformed cells contained pro-alpha 1(I) gene sequences and that the gross structure of the gene was unchanged by transformation. mRNA for the other type I procollagen subunit, pro- alpha 2(I), was present in transformed cells and the major collagenous polypeptide translated from this RNA migrated like the normal pro-alpha 2 subunit during sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The translated procollagen chain was cleaved to an alpha 2(I)-sized collagen chain by pepsin at 4 degrees C. These studies provide a molecular basis for the observed collagen phenotype of NQT- SHE cells.
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