Gordon M K, Gerecke D R, Olsen B R
Proc Natl Acad Sci U S A. 1987 Sep;84(17):6040-4. doi: 10.1073/pnas.84.17.6040.
We have screened a cDNA library constructed from tendon fibroblast mRNA for the presence of collagenous coding sequences. Nucleotide sequence analysis of one isolated clone, pMG377, reveals that the clone encodes a polypeptide that is homologous to, yet distinctly different from, type IX short-chain collagen polypeptides. The structure of the conceptual translation product of the cDNA is also different from that of all other collagen types. Therefore, we have given the type IX-like collagen chain encoded by pMG377 the designation alpha 1(XII). Ribonuclease protection assays with single-stranded cRNA probes demonstrate that alpha 1(XII) mRNA is present in several tissues such as calvaria, tendon, and sternal cartilage of 17-day-old chicken embryo and in cornea from 6-day-old embryos. Using pMG377 as the hybridization probe, we isolated a fragment of the corresponding gene from a chicken genomic library. Partial nucleotide sequence analysis of the genomic clone DG12 shows that the exon/intron structure of the alpha 1(XII) collagen gene appears to be homologous to that of the alpha 1(IX) and alpha 2(IX) collagen genes. Our data demonstrate that types IX and XII collagen are two homologous members of a family of unique collagenous proteins that show tissue-specific patterns of expression. Based on their structure and the properties of their genes, we conclude that this family of collagens is distinctly different from that of fibrillar collagens.
我们从肌腱成纤维细胞mRNA构建的cDNA文库中筛选了是否存在胶原蛋白编码序列。对一个分离克隆pMG377的核苷酸序列分析表明，该克隆编码一种多肽，它与IX型短链胶原蛋白多肽同源，但又明显不同。该cDNA概念翻译产物的结构也与所有其他胶原蛋白类型不同。因此，我们将由pMG377编码的IX型样胶原蛋白链命名为α1（XII）。用单链cRNA探针进行的核糖核酸酶保护试验表明，α1（XII）mRNA存在于17日龄鸡胚的颅盖骨、肌腱和胸骨软骨等多种组织以及6日龄胚胎的角膜中。以pMG377为杂交探针，我们从鸡基因组文库中分离出了相应基因的一个片段。基因组克隆DG12的部分核苷酸序列分析表明，α1（XII）胶原蛋白基因的外显子/内含子结构似乎与α1（IX）和α2（IX）胶原蛋白基因的外显子/内含子结构同源。我们的数据表明，IX型和XII型胶原蛋白是独特胶原蛋白家族的两个同源成员，它们表现出组织特异性的表达模式。基于它们的结构和基因特性，我们得出结论，这个胶原蛋白家族与纤维状胶原蛋白家族明显不同。
