Cloning a cDNA for the pro-alpha 2 chain of human type I collagen

Poly(A)-RNA enriched for type I procollagen sequences was isolated from normal human fibroblasts and used as template to synthesize double-stranded cDNA with avian myeloblastosis virus (AMV) reverse transcriptase. After the ends had been blunted with nuclease S1 and dGMP tails had been added with terminal deoxynucleotidyltransferase, the double-stranded cDNA was annealed with pBR322 DNA that had previously been cleaved with EcoRI, blunted with AMV reverse transcriptase, and dCMP-tailed with terminal deoxynucleotidyltransferase. The chimeric molecule was used to transform Escherichia coli strain HB101. Ninety-five recombinant clones were obtained and screened by dot hybridization analysis using 32P-labeled cDNA synthesized from the original poly(A)-RNA collagen-enriched population. Three positive clones were isolated and further characterized by blot hybridization techniques and by EcoRII digestion. One clone with an insert of 2.2 kilobases was shown to contain sequences encoding for the pro-alpha 2 chain of human type I procollagen. DNA sequence analysis of a 172-nucleotide fragment demonstrated that the cloned cDNA extends from amino acid position 450 of the alpha 2 chain to the middle of the COOH-terminal propeptide.