The DNA binding activity of the paired box transcription factor Pax-3 is rapidly downregulated during neuronal cell differentiation.

Mutations in the murine Pax-3 gene lead to a range of developmental abnormalities including deficiencies in sensory and sympathetic neurones. We have investigated Pax-3 expression during neuronal differentiation and show levels of Pax-3 DNA binding decrease upon cell cycle arrest and morphological differentiation. The fall in Pax-3 DNA binding occurs within 1 h of the induction of differentiation and is mediated in part by a decrease in Pax-3 mRNA. This decrease in Pax-3 binding activity precedes any changes in cell proliferation or morphology, suggesting that the downregulation of this transcription factor may be an important prerequisite for the differentiation of neuronal progenitor cells.