TGF-beta targets PAX3 to control melanocyte differentiation.

In the absence of UV radiation, keratinocytes secrete TGF-beta which blocks melanocyte differentiation. Yang et al. (2008), in a recent issue of Molecular Cell, show that TGF-beta induces Smad signaling in melanocytes to repress PAX3, which encodes a transcription factor crucial for melanocyte differentiation. In the presence of UV radiation, a Jnk/AP-1 pathway represses TGF-beta, which together with a UV-induced p53 pathway promotes melanocyte differentiation.