The type X collagen gene. Intron sequences split the 5'-untranslated region and separate the coding regions for the non-collagenous amino-terminal and triple-helical domains.
Type X collagen, expressed by hypertrophic chondrocytes, consists of homotrimeric molecules with subunits that are only about one-half the size of the polypeptides of fibrillar collagens. In this report we describe for the first time the complete primary structure of type X collagen, based on cloning and sequencing of cDNA and genomic DNA. A comparison between the nucleotide sequences of the cDNA and genomic DNA clones has also allowed determination of the complete exon structure of the type X collagen gene. Our results demonstrate that the primary translation product of the chicken type X collagen mRNA is 682 amino acid residues long with a calculated molecular mass of 67,317 Da for the nonhydroxylated form. This calculated molecular mass is in excellent agreement with the observed electrophoretic mobility of cell-free translation products with both poly(A)+ RNA isolated from chondrocytes as well as RNA transcribed in vitro from a full length cDNA construct. It is also in agreement with the observed size of type X collagen polypeptides isolated from the media of cultured hypertrophic chondrocytes. Thus, our data exclude the possibility of a high molecular weight precursor form of type X collagen. Our results also confirm that the chicken type X gene has a most unusual exon structure when compared to other vertebrate collagen genes. The gene has only three exons. One exon (97 base pairs (bp)), codes for most of the 5'-untranslated region of the mRNA, a second exon (159 bp) codes for the signal peptide and a short non-triple-helical domain, while the third exon (2136 bp) contains the coding region for the entire triple-helix and a large non-triple-helical carboxyl domain.
LuValle
P
P
Department of Anatomy and Cellular Biology, Harvard Medical School, Boston, Massachusetts 02115.
Ninomiya
Y
Y
Rosenblum
N D
ND
Olsen
B R
BR
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002642:Chick Embryo; D003001:Cloning, Molecular; D003094:Collagen / Q000235:genetics*; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D005091:Exons; D005796:Genes; D006132:Growth Plate / Q000378:metabolism; D007438:Introns; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D014158:Transcription, Genetic
D012313:RNA; D003094:Collagen; D004247:DNA