Identification of a new class of PAX3-FKHR target promoters: a role of the Pax3 paired box DNA binding domain.
Alveolar rhabdomyosarcoma (aRMS), an aggressive skeletal muscle cancer, carries a unique t(2;13) chromosomal translocation resulting in the formation of a chimeric transcription factor PAX3-FKHR. This fusion protein contains the intact DNA-binding domains (PD: paired box binding domain; HD: paired-type homeodomain) of Pax3 fused to the activation domain of FKHR. Cells expressing Pax3 and PAX3-FKHR show vastly different gene expression patterns, despite that they share the same DNA-binding domains. We present evidence of a gain of function mechanism that allows the fusion protein to recognize and transcriptionally activate response elements containing a PD-specific binding site. This DNA recognition specificity is in contrast to the requirement for Pax3-specific target sequences that must contain a composite of PD-and HD-binding sites. Domain swapping studies suggest that an increased structural flexibility could account for the relaxed DNA targeting specificity in PAX3-FKHR. Here, we identify myogenin gene as a direct target of PD-dependent PAX3-FKHR activation pathway in vitro and in vivo. We demonstrate that PAX3-FKHR could induce myogenin expression in undifferentiated myoblasts by a MyoD independent pathway, and that PAX3-FKHR is directly involved in myogenin expression in aRMS cells.
Zhang
L
L
Center for Molecular Biology of Oral Diseases, University of Illinois at Chicago, Chicago, IL 60612, USA.
Wang
C
C
D000818:Animals; D047369:Chromatin Immunoprecipitation; D004247:DNA / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000235:genetics*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D018008:Myogenin / Q000235:genetics; D041681:NIH 3T3 Cells; D000072041:PAX3 Transcription Factor; D051761:Paired Box Transcription Factors / Q000235:genetics*; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic
C085126:FOXO1 protein, human; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D018008:Myogenin; D000072041:PAX3 Transcription Factor; C489409:PAX3 protein, human; D051761:Paired Box Transcription Factors; D004247:DNA