CLONING OF TYPE-XVII COLLAGEN - COMPLEMENTARY AND GENOMIC DNA-SEQUENCES OF MOUSE 180-KILODALTON BULLOUS PEMPHIGOID ANTIGEN (BPAG2) PREDICT AN INTERRUPTED COLLAGENOUS DOMAIN, A TRANSMEMBRANE SEGMENT, AND UNUSUAL FEATURES IN THE 5'END OF THE GENE AND THE 3'-UNTRANSLATED REGION OF THE MESSENGER-RNA

Thus far, 16 distinct vertebrate collagens (types I-XVI) have been del ineated. In this study, we have cloned a mouse collagenous protein, th e 180-kDa bullous pemphigoid antigen (BPAG2). Isolation of overlapping clones, together with 5' and 3' rapid amplification of cDNA ends, all owed delineation of the entire coding sequence. The 5' and 3' ends of the mRNA transcripts were confirmed by primer extension and anchored r everse transcription polymerase chain reaction analyses. The deduced p olypeptide contained 1,433 amino acids, including a collagenous domain that consisted of 13 separate segments. Computer analysis of the dedu ced amino acid sequence demonstrated the presence of a membrane-associ ated segment. Examination of the 5' end of the BPAG2 gene revealed tha t the 295-base pair (bp) exon 1 contained two segments of (T)13AA and TT(A)11, whereas exon 2 was shown to contain the translation initiatio n codon. The 3' end of the mRNA transcript identified two 6-bp inverte d repeat sequences that could form a stem for a 30-bp hairpin loop fol lowed by a series of U residues. Comparison of mouse and human BPAG2 s equences demonstrated 86% homology and the unit of evolutionary period of 4.2 million years. In summary, we have cloned full-length mouse BP AG2 cDNA sequences that encode a collagenous polypeptide. We propose t hat this polypeptide be designated as the alpha1-chain of type XVII co llagen.