An enhancer for transcription of collagen IV genes is activated by F9 cell differentiation.

Expression of collagen IV genes is developmentally regulated and cell type-specific. To identify transcriptional control elements for the mouse alpha 2(IV) collagen gene, several promoter constructs were transiently transfected into mouse PYS-2 (parietal yolk sac) cells. Within the 5.5-kb (kilobase) upstream and 8.5-kb downstream sequences from the transcription start site, we have identified several regulatory active regions. Here, we report characterization of the most proximal 0.3-kb enhancer found at 4.5-kb upstream of the alpha 2(IV) collagen gene. This enhancer is transcriptionally active in cells that make collagen IV such as PYS-2 cells and differentiated F9 cells, but has little if any activity in cells that do not make collagen IV including NIH 3T3 cells and undifferentiated F9 embryonal carcinoma stem cells. This enhancer, linked to the herpes simplex virus TK gene promoter, confers a cell type-specific and differentiation-induced expression on the TK gene as well. Mutational and 5' and 3' deletion analysis demonstrate that this enhancer activity requires two identical response elements (GAACAAT) present in the 0.3-kb enhancer sequence. In gel shift assay, the GAACAAT element forms a complex that is specific for cells that make collagen IV.