title: Microphthalmia-associated transcription factor regulates RAB27A gene expression and controls melanosome transport.
abstract: Melanosomes are lysosome-related organelles specialized in melanin synthesis and transport. In this study, we show that microphthalmia-associated transcription factor (MITF) silencing induces melanosome gathering around the nucleus and causes the relocalization of Rab27A, Slac2a-Mlph, and Myo5a that control the transport of melanosomes on the actin network. In an attempt to elucidate the mechanism by which MITF controls melanosome distribution, we identify RAB27A as a new MITF target gene. Indeed, MITF silencing leads to a dramatic decrease in Rab27A expression and blocks the stimulation of Rab27A expression evoked by cAMP. Further, forced expression of MITF increases Rab27A expression, indicating that MITF is required and sufficient for Rab27A expression in melanoma cells. MITF binds to two E-boxes in the proximal region of the Rab27A promoter and stimulates its transcriptional activity. Finally, re-expression of Rab27A, in MITF-depleted cells, restores the transport of melanosomes to the cell periphery. These results show that RAB27A is a new direct transcriptional target of MITF and link MITF to melanosome transport, another key parameter of melanocyte differentiation and skin pigmentation. Interestingly, Rab27A is involved in other fundamental physiological functions, such as the transport of lytic granules and insulin secretion. Thus our results, deciphering the mechanism of Rab27A transcriptional regulation, have an interest that goes beyond the skin pigmentation field.
authors.affiliation: INSERM U895, Biologie et Pathologies des Cellules Mélanocytaires de la Pigmentation Cutanée au Mélanome 28, avenue de Valombrose, 06107 Nice Cedex 2, France.
authors.forename: Christine
authors.initials: C
authors.lastname: Chiaverini
authors.forename: Laurent
authors.initials: L
authors.lastname: Beuret
authors.forename: Enrica
authors.initials: E
authors.lastname: Flori
authors.forename: Roser
authors.initials: R
authors.lastname: Busca
authors.forename: Patricia
authors.initials: P
authors.lastname: Abbe
authors.forename: Karine
authors.initials: K
authors.lastname: Bille
authors.forename: Philippe
authors.initials: P
authors.lastname: Bahadoran
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Ortonne
authors.forename: Corine
authors.initials: C
authors.lastname: Bertolotto
authors.forename: Robert
authors.initials: R
authors.lastname: Ballotti
mesh_terms: D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D001692:Biological Transport; D045744:Cell Line, Tumor; D024721:E-Box Elements / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D020460:Melanosomes / Q000378:metabolism*; D051379:Mice; D051739:Microphthalmia-Associated Transcription Factor / Q000172:deficiency / Q000378:metabolism*; D008969:Molecular Sequence Data; D024701:Myosin Type V / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D014158:Transcription, Genetic; D020691:rab GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D000075745:rab27 GTP-Binding Proteins
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D051739:Microphthalmia-Associated Transcription Factor; C435724:Mlph protein, mouse; D000075745:rab27 GTP-Binding Proteins; D024701:Myosin Type V; C066694:RAB27A protein, human; C512962:Rab27a protein, mouse; D020691:rab GTP-Binding Proteins