Identification of DNA recognition sequences for the Pax3 paired domain

The Pax gene family, encoding transcription factors, has been classified into four subfamilies according to their genomic organization, the sequences of the paired domains (PD) and the expression pattern. Pax1 and Pax9 constitute one subfamily, Pax2, Pax5 and Pax8 another, Pax3 and Pax7 another one and Pax4 and Pax6 the fourth subfamily. The PD exhibits DNA-binding activity, and is the most conserved functional motif in all Pax proteins. A high-resolution analysis of a PD structure has been performed [Xu et al., Cell 80 (1995) 639-650] and the DNA-binding characteristics of members of two Pax subfamilies (Pax2, Pax5 and Pax6) have been determined. Here, we have utilized a PCR-based selection approach to identify the DNA-binding sequences of the Pax3/PD, a member of a subfamily which has not yet been characterized. Comparison of the Pax3/PD-binding sequences with those of other PD proteins revealed both similarities and differences in the DNA-recognition sequence. This suggests that different Pax proteins can regulate the expression of the same target gene, but they can also regulate the expression of completely unrelated genes by binding to their DNA regulatory regions.