Elsevier

Genomics

Volume 11, Issue 1, September 1991, Pages 145-153
Genomics

The exon organization of the triple-helical coding regions of the human α1(VI) and α2(VI) collagen genes is highly similar

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Abstract

The α1(VI) and α2(VI) chains, two of the three constituent chains of type VI collagen, are highly similar in size and domain structure. They are encoded by single-copy genes residing in close proximity on human chromosome 21. To study the evolution of the type VI collagen genes, we have isolated and characterized genomic clones coding for the triple-helical domains of the human α1(VI) and α2(VI) chains, which consist of 336 and 335 amino acid residues, respectively. Nucleotide sequencing indicates that, in both genes, the exons are multiples of 9 bp in length (including 27, 36, 45, 54, 63, and 90 bp) except for those encoding for regions with triple-helical interruptions. In addition, the introns are positioned between complete codons. The most predominant exon size is 63 bp, instead of 54 bp as seen in the fibrillar collagen genes. Of particular interest is the finding that the exon structures of the α1(VI) and α2(VI) genes are almost identical. A significant deviation is that a segment of 30 amino acid residues is encoded by two exons of 54 and 36 bp in the α1(VI) gene, but by a single exon of 90 bp in the α2(VI) gene. The exon arrangement therefore provides further evidence that the two genes have evolved from tandem gene duplication. Furthermore, comparison with the previously reported gene structure of the chick α2(VI) chain indicates that the exon structure for the triple-helical domain of the α2(VI) collagen is strictly conserved between human and chicken.

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  • Cited by (0)

    1

    On leave of absence from Istituto di Biologia dello Sviluppo, CNR, Palermo, Italy.

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