Evaluation of mRNA steady-state and protein levels for basement membrane proteins in cultured murine cells

We have determined the mRNA steady-state levels for the six constituent polypeptide chains of the basement membrane proteins collagen IV, laminin and nidogen in murine cell lines derived from a teratocarcinoma, and in some other cell lines of different origin in stationary cultures and during different growth phases. The mRNA and protein levels change in response to growth phase. The amounts of the mRNAs for the single chains do not agree with the ratios needed for the different peptide chains of collagen IV and laminin. While the mRNA and protein levels for laminin are in a similar range for the teratocarcinoma-derived cell lines, the mRNA and protein levels vary by at least a factor of 10 for collagen IV. These results point to complex posttranscriptional regulatory mechanisms for the biosynthesis of basement membrane proteins.