Identification of an FGF-responsive element in the 1.3 kb mouse c-Maf promoter. A, schematic diagram of the mouse c-Maf locus, including the distal enhancer CR1 active in the lens, 1.3-kb promoter, and evolutionarily conserved blocks, and the EGFP reporter construct containing the 1.3 kb c-Maf promoter. B, expression of the 1.3-kb c-Maf promoter-EGFP reporter construct in transiently transfected primary cultures of chicken lens cells in the absence or presence of FGF2. C, diagram of WT and three deletion mutants (M1-M3) of the c-Maf promoter-EGFP reporter constructs. D, semi-quantitative EGFP reporter expression analysis (Western blot, β-actin used as loading control) after transient expression of constructs in primary cultures of chicken lens cells treated with (+FGF) or without (−FGF) FGF2 for 6 days. Note that the M2-reporter was tested at 2-fold DNA concentration. E, diagram of 3xFRE (−272/−70)/luc plasmid. F, analysis of 3XFRE-luc in the presence (+FGF) and absence (−FGF) FGF2 in DCDMLs.