Involvement of ITF2 in the transcriptional regulation of melanogenic genes

In response to agouti signal protein, melanocytes switch from producing eum elanin to pheomelanin concomitant with the down-regulation of melanogenic g ene transcription. We previously reported that a ubiquitous basic helix-loo p-helix transcription factor, known as ITF2, is up-regulated during this sw itch, and we now report that treatment of melanocytes with melanocyte-stimu lating hormone down-regulates expression of ITF2. To more fully characteriz e the involvement of ITF2 in regulating melanogenic gene transcription, ITF 2 sense or antisense constructs were introduced into melan-a melanocytes. G ene and protein expression analyses and luciferase reporter assays using pr omoters from melanogenic genes showed that up-regulation of ITF2 suppressed melanogenic gene expression as well as the expression of Mitf, a melanocyt e-specific transcription factor. In addition, stable ITF2 sense transfectan ts had significant reductions in pigmentation and a less dendritic phenotyp e compared with mock transfectants. In contrast, ITF2 antisense-transfected melanocytes were more pigmented and more dendritic. These results demonstr ate that up-regulation of ITF2 during the pheomelanin switch is functionall y significant and reveal that differential expression of a ubiquitous basic helix-loop-helix transcription factor can modulate expression of melanogen ic genes and the differentiation of melanocytes.