title: Microphthalmia-associated transcription factor is a critical transcriptional regulator of melanoma inhibitor of apoptosis in melanomas.
abstract: Melanoma inhibitor of apoptosis (ML-IAP) is a potent inhibitor of apoptosis, which is highly expressed in melanomas and likely contributes to their resistance to chemotherapeutic treatments. Herein, we show that the lineage survival oncogene microphthalmia-associated transcription factor (MITF) is a critical regulator of ML-IAP transcription in melanoma cells. The ML-IAP promoter contains two MITF consensus sites, and analysis of MITF and ML-IAP mRNA levels revealed a high correlation in melanoma tumor samples and cell lines. In reporter assays, MITF promoted a strong stimulation of transcriptional activity from the ML-IAP promoter, and MITF bound the endogenous ML-IAP promoter in melanoma cells by chromatin immunoprecipitation and electrophoretic mobility shift assay. Strikingly, small interfering RNA (siRNA)-mediated knockdown of MITF in melanoma cells led to a dramatic decrease in ML-IAP mRNA and protein levels, establishing that ML-IAP expression in melanoma cells is MITF dependent. Additionally, cyclic AMP-mediated induction of MITF expression in melanocytes resulted in increased ML-IAP expression, suggesting that melanocytes can express ML-IAP when MITF levels are heightened. Disruption of MITF by siRNA led to a decrease in melanoma cell viability, which could be rescued by ectopic expression of ML-IAP. Collectively, these findings implicate MITF as a major transcriptional regulator of ML-IAP expression in melanomas, and suggest that ML-IAP contributes to the prosurvival activity of MITF in melanoma progression.
authors.affiliation: Department of Protein Engineering, Genentech, Inc., South San Francisco, California 94080, USA.
authors.forename: Jasmin N
authors.initials: JN
authors.lastname: Dynek
authors.forename: Sara M
authors.initials: SM
authors.lastname: Chan
authors.forename: Jinfeng
authors.initials: J
authors.lastname: Liu
authors.forename: Jiping
authors.initials: J
authors.lastname: Zha
authors.forename: Wayne J
authors.initials: WJ
authors.lastname: Fairbrother
authors.forename: Domagoj
authors.initials: D
authors.lastname: Vucic
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics*; D002470:Cell Survival / Q000235:genetics; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D004249:DNA Damage / Q000502:physiology; D005786:Gene Expression Regulation; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics*; D008544:Melanocytes / Q000378:metabolism; D008545:Melanoma / Q000235:genetics*; D051739:Microphthalmia-Associated Transcription Factor / Q000378:metabolism / Q000502:physiology*; D009363:Neoplasm Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D015398:Signal Transduction / Q000235:genetics; D014158:Transcription, Genetic; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology; D051153:Wnt Proteins / Q000502:physiology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C419866:BIRC7 protein, human; D051034:Inhibitor of Apoptosis Proteins; D051739:Microphthalmia-Associated Transcription Factor; D009363:Neoplasm Proteins; D014409:Tumor Necrosis Factor-alpha; D051153:Wnt Proteins; D000242:Cyclic AMP