A transcriptional enhancer has been identified in the first intron of the mouse alpha 2 (type I) collagen gene in a region between +418 and +1524 base pairs from the transcriptional start site. The enhancer functions both when it is located 5' and 3' to the promoter that it activates and is independent of the orientation of the element. The enhancer stimulates both the homologous alpha 2 type I [alpha 2(I)] collagen promoter and the heterologous early simian virus 40 promoter. In transient expression experiments, enhancer-dependent transcription from the alpha 2(I) collagen promoter utilizes the same transcriptional start site as the one used in the endogenous alpha 2(I) collagen gene. The enhancer activates transcription at a distance of at least 3 kilobase pairs from the transcriptional start site. The alpha 2(I) collagen enhancer displays cell specificity, since it is functional in NIH 3T3 fibroblasts but completely inactive in a lymphoid cell line, in contrast to two immunoglobulin gene enhancers that show the opposite behavior. We find several areas of sequence homology with viral enhancers, particularly the enhancer of simian virus 40.

Rossi, P., & de Crombrugghe, B. (1987). Identification of a cell-specific transcriptional enhancer in the first intron of the mouse alpha 2 (type I) collagen gene. Proceedings of the National Academy of Sciences, 84(16), 5590–5594.