Transcriptional promoter of the human α1(V) collagen gene (COL5A1)

We have characterized the 5′ region of the human alpha 1(V) collagen gene (COL5A1). The transcriptional promoter is shown to have a number of features characteristic of the promoters of ‘housekeeping’ and growth-control-related genes. It lacks obvious TATA and CAAT boxes, has multiple transcription start sites, has a high GC content, lies within a well-defined CpG island and has a number of consensus sites for the potential binding of transcription factor Sp1. This type of promoter structure, while unusual for a collagen gene, is consistent with the broad distribution of expression of COL5A1 and is reminiscent of the promoter structures of the genes encoding type VI collagen, which has a similarly broad distribution of expression. Stepwise deletion of COL5A1 5′ sequences, placed upstream of a heterologous reporter gene, yielded a gradual decrease in promoter activity, indicating that the COL5A1 promoter is composed of an array of cis-acting elements. A minimal promoter region contained within the 212 bp immediately upstream of the major transcription start site contained no consensus sequences for the binding of known transcription factors, but gel mobility shift assays showed this region to bind nuclear factors, including Sp1, at a number of sites. The major transcription start site is flanked by an upstream 34-bp oligopurine/oligopyrimidine stretch, or ‘GAGA’ box, and a downstream 56-bp GAGA box which contains a 10-bp mirror repeat and is sensitive to cleavage with S1 nuclease.