Alpha 1(IV) and alpha 2(IV) collagen genes are regulated by a bidirectional promoter and a shared enhancer.

Collagen IV is the major structural component of basement membranes and is a heterotrimer composed of two alpha 1(IV) and one alpha 2(IV) chains. Most collagen genes are dispersed in the human genome, such as the genes for collagen I, which are located on chromosomes 7 [alpha 1(I)] and 17 [alpha 2(I)]. In contrast, we have found that the murine alpha 1(IV) and alpha 2(IV) collagen chain genes exist in a head-to-head arrangement on opposite strands separated by 130 base pairs. By transfecting various portions of these genes into cells, we have found that transcription of the alpha 1(IV) and alpha 2(IV) genes is regulated by a bidirectional promoter located between the two genes working in concert with an enhancer located in the first intron of the alpha 1(IV) chain gene.