THE PROMOTER OF THE CHICKEN ALPHA-2(VI) COLLAGEN GENE HAS FEATURES CHARACTERISTIC OF HOUSE-KEEPING GENES AND OF PROTOONCOGENES

The promoter of the chicken alpha-2(VI) collagen gene reveals several interesting features characteristic of house-keeping genes and growth control related genes. It does not possess a typical TATAA or CAAT box, but it contains several potential binding sites for transcription factors Sp1 and ETF. The 5' flanking region of the gene forms a typical 'CpG island' where the dinucleotide sequence CpG occurs with high frequency relative to the bulk genome. Consistent with the lack of a TATAA element, the gene contains multiple transcription initiation sites distributed over 75 bp of genomic DNA. A short DNA fragment (207 bp) encompassing all the transcription initiation sites and the entire CpG island shows strong promoter activity when linked to a heterologous reporter gene. The upstream region of the promoter harbours a long homopurine/homopyrimidine element (403 bp) which is sensitive to endonuclease S1. This element might have the ability to adopt an intramolecular hairpin triplex structure and could play a role in the organization of the chromatin at the alpha-2(VI) collagen locus. Our results demonstrate that the structure of the alpha-2(VI) collagen promoter is completely different from that of any other collagen promoter characterized so far.