TFE3, a transcription factor homologous to microphthalmia, is a potential transcriptional activator of tyrosinase and TyrpI genes.
Microphthalmia gene encodes a basic helix-loop-helix-leucine zipper (bHLH-Zip) transcription factor involved in the development of the melanocyte lineage and plays a key role in the transcriptional regulation of the melanogenic enzymes, tyrosinase and TyrpI. Recently, we have shown that Microphthalmia mediates the melanogenic effects elicited by alphaMSH that up-regulates the expression of tyrosinase through the activation of the cAMP pathway. Therefore, Microphthalmia appears as a principal gene in melanocyte development and functioning. Among the transcription factors of the bHLH-Zip family, TFE3 and TFEB show a remarkably elevated homology with Microphthalmia. These observations prompted us to investigate the role of TFE3 and TFEB in the regulation of tyrosinase and TyrpI gene transcription. We show in this report that overexpression of TFE3 stimulates the tyrosinase and TyrpI promoter activities, while TFEB acts only on the TyrpI promoter. TFE3 and TFEB elicit their effects mainly through the binding to Mbox (AGTCATGTGCT) and Ebox motifs (CATGTG) of tyrosinase and TyrpI promoters. In B16 melanoma cells, the high basal expression of TFE3 is down-regulated by forskolin and by alphaMSH. Interestingly, endogenous TFE3 cannot bind as homodimers to the Mbox, and we did not detect TFE3/Mi heterodimers. According to these data, TFE3 is clearly endowed with the capacity to regulate tyrosinase and TyrpI gene expression. However, TFE3 binding to the melanogenic gene promoters is hindered, thereby preventing its potential melanogenic action. In specific physiological or pathological conditions, the recovery of its binding function would make TFE3 an important element in melanogenesis regulation.
Verastegui
C
C
Institut National de la Santé et de la Recherche Médicale U385, Faculté de Médecine, Nice, France.
Bertolotto
C
C
Bille
K
K
Abbe
P
P
Ortonne
J P
JP
Ballotti
R
R
D016475:3T3 Cells; D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D019281:Dimerization; D005786:Gene Expression Regulation; D006367:HeLa Cells; D018257:Helix-Loop-Helix Motifs / Q000235:genetics / Q000502:physiology; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism; D016350:Leucine Zippers / Q000235:genetics / Q000502:physiology; D008543:Melanins / Q000378:metabolism; D008544:Melanocytes / Q000187:drug effects / Q000378:metabolism; D008546:Melanoma, Experimental / Q000473:pathology; D008562:Membrane Glycoproteins; D051379:Mice; D051739:Microphthalmia-Associated Transcription Factor; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D010088:Oxidoreductases; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000502:physiology; D015290:Second Messenger Systems / Q000187:drug effects; D017384:Sequence Deletion; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors / Q000737:chemistry / Q000502:physiology*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D000521:alpha-MSH / Q000502:physiology
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; C497234:MITF protein, human; D008543:Melanins; D008562:Membrane Glycoproteins; D051739:Microphthalmia-Associated Transcription Factor; C497235:Mitf protein, mouse; D011506:Proteins; D011993:Recombinant Fusion Proteins; C069203:TFE3 protein, human; D014157:Transcription Factors; D005576:Colforsin; D000521:alpha-MSH; D000242:Cyclic AMP; D010088:Oxidoreductases; C489799:TYRP1 protein, human; C079621:Tyrp1 protein, mouse; C064056:tyrosinase-related protein-1; D014442:Monophenol Monooxygenase