Construction of a cDNA clone corresponding to mouse alpha 1(IV) procollagen

Cell-free translation products of basement membrane RNA from the EHS tumor

The biosynthetic products of the Engelbreth-Holm-Swarm (EHS) tumor and the cell-free translation products of EHS tumor cell RNA were characterized. Six distinct gene products (three laminin polypeptides, entactin/nidogen, and two collagen IV chains) comprising the basement membrane matrix were identified by a combination of proteolytic digestion and immunologic techniques. Analysis of the cell-free translation products using EHS tumor RNA precipitated by anti-laminin serum confirms earlier evidence that there are at least two B chains encoded by different genes. The anti-laminin serum also recognized entactin/nidogen, which was further identified by specific immunoprecipitation with anti-entactin serum. Radiolabeled laminin A chains, synthesized by the EHS tumor in organ culture, were also identified by the anti-laminin serum but were not detected among the cell-free translation products of EHS tumor RNA. Pulse-chase studies of EHS tumor in organ culture as well as in vitro translation of EHS tumor RNA suggest that the precursor forms of alpha 1(IV) and alpha 2(IV) collagen chains are nearly identical in size, with apparent molecular weights of 170,000. The mRNAs encoding these two polypeptides migrate differently on sucrose gradients. It is likely that glycosylation and hydroxylation of collagen IV account for the major differences in molecular weight of mature alpha 1(IV) and alpha 2(IV) chains in the EHS tumor matrix.

Isolation of an alpha 1 type-IV collagen cDNA clone using a synthetic oligodeoxynucleotide

We have isolated a cDNA clone (pCIV-1-225) for the alpha 1 subunit of basement membrane (type IV) collagen from a cDNA library made from Engelbreth-Holm-Swarm mouse tumor RNA. The cDNA library was screened with synthetic oligodeoxynucleotides derived from published amino acid (aa) sequences (Schuppan et al., 1982). Nucleotide sequence data established the identity of our cDNA clone to encode an alpha 1 type IV collagen. This clone contains 270 aa of the helical region and has three interruptions in the Gly-X-Y repeat unit.

Amino acid sequence of the non-collagenous globular domain (NC1) of the alpha 1(IV) chain of basement membrane collagen as derived from complementary DNA

NC1, the C-terminal non-collagenous globular domain of collagen IV, represents one of the two end regions responsible for the assembly and cross-linking of the extracellular network of basement membrane collagen. Several cDNA clones for the NC1 domain of the alpha 1(IV) collagen chain of mouse have been isolated by using synthetic oligonucleotides as screening probes for mouse libraries. The oligonucleotides were synthesized according to known stretches of the corresponding protein sequence. Sequencing of the overlapping cDNA clones allowed the complete amino acid sequence of the NC1 domain to be deduced as well as the C-terminal 165 amino acid residues of the triple helix. It consists of 229 amino acid residues which comprise two homologous regions with a high content of cysteine. These DNA and protein sequences are compared to the corresponding sequences of other collagens and discussed with respect to their structural and biological significance.