EGR1 and melanoma: Based on the above results, we decided to create ERK activity reporter cell lines by stably transfecting A375 and MelJuso cells with the reporter construct pKROX24(MapErk)Luc, expressing firefly luciferase under the control of an EGR1 gene-derived promoter to study the eIF4F-mediated control of MAPK optimum in melanoma (29).