Molecular cloning of the bovine alpha 1(IV) procollagen gene (COL4A1) and its use in investigating the regulation of expression of type IV procollagen by retinoic acid in bovine lens epithelial cells.

This report is the first to describe the isolation of a 400 base pair cDNA clone encoding part of the bovine alpha 1(IV) procollagen. Using the polymerase chain reaction (PCR), we have amplified a sequence of approximately 400 bp from this gene within the recombinant phage DNA. The cloned sequence encodes 94 amino acids that form part of the protein's helical region. The sequence contains one interruption in the Gly-Xaa-Yaa repeat unit. The third base of the codon for glycine at several sites differs from those seen in murine and human genes, as does the third base of proline codons. The bovine cDNA also contains fewer thymine residues. Northern blot hybridization has shown that the mRNA for bovine procollagen to be 6.2 kb in size. We have used the cDNA clone to investigate the effect of all-trans retinoic acid (RA) on the gene expression of alpha 1(IV) procollagen in cultured bovine lens epithelial (LE) cells. We have also observed that RA decreases total protein production and concomitantly increases type IV procollagen in a concentration dependent manner. An increase in alpha 1(IV)mRNA as well as increase in type IV procollagen suggest that the regulation of alpha 1(IV) gene by RA in the LE cells is at the transcriptional level. Further, our results support the hypothesis that RA inhibition of lens epithelium transformation to fibroblast-like cells may be due to the ability of RA to stimulate the production of basement membrane components by epithelia.