Paired box 3-Forkhead box O1 fusion protein (PAX3-FOXO1)

The Paired box 3-Forkhead box O1 (PAX3-FOXO1) fusion protein is a chimeric transcription factor resulting from a reciprocal chromosomal translocation, t(2;13)(q35;q14), which is the primary oncogenic driver in approximately 80% of alveolar rhabdomyosarcoma (ARMS) cases (PMID: 30610214). This fusion protein combines the N-terminal DNA-binding domain of PAX3 with the C-terminal transactivation domain of FOXO1 (formerly known as FKHR), creating a potent activator that bypasses normal regulatory controls (PMID: 25103342). It promotes tumorigenesis by upregulating genes involved in cell survival (IGF1R), proliferation (MYCN), and migration (MET), while simultaneously blocking terminal myogenic differentiation (PMID: 29138268). Although transcription factors like PAX3-FOXO1 are traditionally considered difficult to target directly with small molecules, current research focuses on disrupting its interaction with epigenetic modifiers like HDACs or BRD4, and inhibiting its downstream signaling pathways (PMID: 31515458). Understanding the structural biology of this fusion is critical for developing precision therapies for pediatric patients with high-risk ARMS.

Other names

PAX3-FKHRt(2;13)(q35;q14) fusion proteinPAX3/FOXO1Forkhead in rhabdomyosarcoma fusion protein

The fusion protein acts as a potent chimeric transcription factor that binds to PAX3 DNA-binding sites and utilizes the FOXO1 transactivation domain to constitutively activate oncogenic target genes (PMID: 25103342).