Partial structure of the gene for chicken cartilage proteoglycan core protein

A genomic DNA fragment (gCORE-1), encoding a portion of the cartilage proteoglycan core protein, has been isolated from a phage library using cDNA as a probe. The genomic insert is about 17 kilobase pairs; two BamHI fragments of the insert (1.3 and 4.8 kilobase pairs) contain most of the hybridizable sequences found in the cDNA. Sequence analysis of these fragments shows that they contain a total of five exons that encompass 216 amino acid residues, all of which are identical to those of the corresponding cDNA sequence. Three of the exons, which are adjacent to one another, are very similar to the corresponding exons in the gene of a rat hepatic lectin as well as to an exon in the gene of human pulmonary surfactant-associated protein. There is a strong degree of conservation of amino acid sequences encoded in the three genes, although there is no similarity between their introns. The sizes of the five exons in gCORE-1, except for one (which is indeterminate because only a partial cDNA sequence is available), are less than 184 base pairs, whereas the sizes of the introns range from 218 to greater than 2629 base pairs. Four of the introns interrupt an exon codon at either their donor or acceptor sites, between the first and second nucleotides. Only one intron does not split a codon. Intron and exon boundary sites are in agreement with known consensus sequences for introns. The dispersed distribution and relatively small size of the exons, if representative of the entire gene, suggest that the complete gene which codes for the core protein may be quite sizable.