MITF and melanoma: To explore the regulatory mechanism of CDK7 transcription, we first treated several MITF-dependent melanoma lines under MITF-directed RNAi with 12-O-tetradecanoylphorbol-13-acetate (TPA), a potent activator of protein kinase C. TPA leads to activation of MAP kinase and subsequent phosphorylation of MITF S73 which mediates upregulation of transcriptional activity of MITF [33].