PAXBP1 encodes the PAX3 And PAX7 Binding Protein 1 that may bind to GC-rich DNA sequences, which suggests its involvement in the regulation of transcription. Alternative splicing of this gene results in multiple transcript variants. Adapter protein linking the transcription factors PAX3 and PAX7 to the histone methylation machinery and involved in myogenesis. Associates with a histone methyltransferase complex that specifically mediates dimethylation and trimethylation of Lys-4 of histone H3. Mediates the recruitment of that complex to the transcription factors PAX3 and PAX7 on chromatin to regulate the expression of genes involved in muscle progenitor cells proliferation including ID3 and CDC20 (By similarity).