Transfection experiments. Schematic representation of MC1R-Luciferase reporter constructs and corresponding activities after transfection into MeWo, NIH3T3 and HeLa cell lines. A. We schematically illustrate, as empty box, the MC1R promoters driving the luciferase gene shown as a black box. The arrow schematically represents the major start of transcription as we have determined it by primer extension experiments both in MeWo and in NIH3T3 cells transfected with the pFull vector (data not shown). It is worth to mention that this result is in agreement with the start of transcription of the human MC1R gene previously reported , . M, A, Bs and Bg indicate the restriction enzymes Mlu1, Aat2, BssH2 and Bgl2, respectively. B. pFull and the described deletion mutants have been transfected in MeWo, NIH 3T3 and HeLa cell lines. The promoter activity in MeWo (black), NIH 3T3 (gray) and Hela (stripe) are reported as percentage of the SV40 promoter of pGL3 Promoter vector arbitrarily considered as 100. The pBig promoter activity has been compared with the pGL3 Control activity, and in this case the transcriptional activity of pGL3 Control was arbitrarily considered, in all cell lines, as 100.