title: PAX3-FKHR transformation increases 26 S proteasome-dependent degradation of p27Kip1, a potential role for elevated Skp2 expression.
abstract: PAX3-FKHR is an oncogenic form of the developmental regulator Pax3 transcription factor. PAX3-FKHR results from a t(2,13) chromosomal translocation, a unique genetic marker of alveolar rhabdomyosarcoma. In this study, we showed that ectopic expression of PAX3-FKHR, but not Pax3, in fibroblasts altered cell cycle control and accelerated G(0)/G(1) to S cell cycle transition. PAX3-FKHR-expressing cells had reduced expression of p27(Kip1) protein, a key cell cycle regulator. The reduction in p27(Kip1) levels by PAX3-FKHR resulted from destabilization of p27(Kip1) as shown by cycloheximide treatment and in vivo pulse-chase labeling experiments. The reduced p27(Kip1) protein level in PAX3-FKHR-expressing cells was restored to the level of control cells by treatment with chemical inhibitors that specifically blocked 26 S proteasome activity. Along with the reduction in p27(Kip1) protein, PAX3-FKHR-expressing cells exhibited elevated expression of F-box Skp2 protein, a substrate-specific component of SCF (Skp1-Cullin-F box protein) ligase involved in the cell cycle-dependent control of p27(Kip1) ubiquitination and 26 S proteasome dependent degradation. Finally, we showed that ectopic expression of p27(Kip1) in PAX3-FKHR-expressing cells significantly reduced the proliferation and colony-forming potential of these cells, implicating that down-regulation of p27(Kip1) protein played an active role in the PAX3-FKHR-directed cell transformation.
authors.affiliation: Center for Molecular Biology of Oral Diseases, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Chiayeng
authors.initials: C
authors.lastname: Wang
mesh_terms: D016475:3T3 Cells; D000293:Adolescent; D000818:Animals; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002471:Cell Transformation, Neoplastic; D002648:Child; D051357:Cyclin-Dependent Kinase 2; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D016147:Genes, Tumor Suppressor; D006801:Humans; D051379:Mice; D000072041:PAX3 Transcription Factor; D051761:Paired Box Transcription Factors; D010447:Peptide Hydrolases / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D012208:Rhabdomyosarcoma / Q000378:metabolism; D044786:S-Phase Kinase-Associated Proteins; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C085126:FOXO1 protein, human; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; C467200:Foxo1 protein, mouse; D000072041:PAX3 Transcription Factor; C489409:PAX3 protein, human; D051761:Paired Box Transcription Factors; D011993:Recombinant Fusion Proteins; D044786:S-Phase Kinase-Associated Proteins; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C068686:Pax3 protein, mouse; D050760:Cyclin-Dependent Kinase Inhibitor p27; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D010447:Peptide Hydrolases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease