Mechanism of PAX3-FKHR in transcriptional regulation

[[abstract]]The PAX3-FKHR fusion protein is formed as a result of t(2;13) chromosomal translocations and functions as a transcription factor to activate transcription. In the clinical sense of cancer research, PAX3-FKHR is the pathogenetic marker for alveolar rhabdomyosarcoma. During the development cycle of skeletal muscles, gene expression is controlled by transcription that requires regulation of transcription factors. PAX3-FKHR is characterized by the t(2;13) chromosomal translocation, which results in the fusion of two transcription factors, PAX3 and FKHR, in rhabdomyosarcoma. The protein structure and function of PAX3-FKHR is similar to those of PAX3, with a much greater transcriptional activity ability. However, the mechanism of PAX3-FKHR in transcriptional regulation is still unknown. It is reported that PAX3 regulates transcriptional activity through protein-protein interactions. In this thesis we want to investigate the mechanism of PAX3-FKHR in transcriptional regulation. It has been shown that corepressor KAP1 and histone modifiers, through interacting with PAX3, affect the transcriptional activity of PAX3. We hypothesize that PAX3-FKHR modulates its transcriptional activity through protein-protein interactions. We tried to find proteins interacting with PAX3-FKHR by co-immunoprecipitation. Our results show that PAX3-FKHR, through interacting with KAP1, decreases its activation transcriptional activity in transcriptional assay. Further we find that PAX3-FKHR interacts with histone modifiers, including HDAC10, SIRT1, SIRT6, SIRT7 and JMJD2A. We also find that JMJD2A, through interacting with PAX3-FKHR, increases the activation transcriptional activity of PAX3-FKHR. We already know that PAX3-FKHR and PAX3 have the same DNA binding domains and they both function as transcription factors. After understanding the relationship between PAX3-FKHR and its transcriptional associated proteins, we want to determine if PAX3-FKHR competes with PAX3’s target promoters, MITF, TRP-1 and TRP-2 promoters, and affects its activation activity. Our results show that PAX3-FKHR and PAX3 affect each other’s transcriptional activity. These results suggest that corepressor KAP1 and histone modifier JMJD2A affect the mechanism of PAX3-FKHR in transcriptional regulation. PAX3-FKHR competes with PAX3 on PAX3 target promoters and affects the transcriptional activity of PAX3