title: A conserved motif N-terminal to the DNA-binding domains of myogenic bHLH transcription factors mediates cooperative DNA binding with pbx-Meis1/Prep1.
abstract: The t(1;19) chromosomal translocation of pediatric pre-B cell leukemia produces chimeric oncoprotein E2a-Pbx1, which contains the N-terminal transactivation domain of the basic helix-loop-helix (bHLH) transcription factor, E2a, joined to the majority of the homeodomain protein, Pbx1. There are three Pbx family members, which bind DNA as heterodimers with both broadly expressed Meis/Prep1 homeo-domain proteins and specifically expressed Hox homeodomain proteins. These Pbx heterodimers can augment the function of transcriptional activators bound to adjacent elements. In heterodimers, a conserved tryptophan motif in Hox proteins binds a pocket on the surface of the Pbx homeodomain, while Meis/Prep1 proteins bind an N-terminal Pbx domain, raising the possibility that the tryptophan-interaction pocket of the Pbx component of a Pbx-Meis/Prep1 complex is still available to bind trypto-phan motifs of other transcription factors bound to flanking elements. Here, we report that Pbx-Meis1/Prep1 binds DNA cooperatively with heterodimers of E2a and MyoD, myogenin, Mrf-4 or Myf-5. As with Hox proteins, a highly conserved tryptophan motif N-terminal to the DNA-binding domains of each myogenic bHLH family protein is required for cooperative DNA binding with Pbx-Meis1/Prep1. In vivo, MyoD requires this tryptophan motif to evoke chromatin remodeling in the Myogenin promoter and to activate Myogenin transcription. Pbx-Meis/Prep1 complexes, therefore, have the potential to cooperate with the myogenic bHLH proteins in regulating gene transcription.
authors.affiliation: Department of Basic Science, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
authors.forename: P S
authors.initials: PS
authors.lastname: Knoepfler
authors.forename: D A
authors.initials: DA
authors.lastname: Bergstrom
authors.forename: T
authors.initials: T
authors.lastname: Uetsuki
authors.forename: I
authors.initials: I
authors.lastname: Dac-Korytko
authors.forename: Y H
authors.initials: YH
authors.lastname: Sun
authors.forename: W E
authors.initials: WE
authors.lastname: Wright
authors.forename: S J
authors.initials: SJ
authors.lastname: Tapscott
authors.forename: M P
authors.initials: MP
authors.lastname: Kamps
mesh_terms: D016475:3T3 Cells; D000495:Allosteric Site; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017124:Conserved Sequence / Q000235:genetics; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D018398:Homeodomain Proteins / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D018006:Myogenic Regulatory Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism*; D000075062:Pre-B-Cell Leukemia Transcription Factor 1; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D020218:Response Elements / Q000235:genetics; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014364:Tryptophan / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; C000616391:MEIS1 protein, human; C000616392:Meis1 protein, mouse; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D018006:Myogenic Regulatory Factors; D009363:Neoplasm Proteins; C106682:PKNOX1 protein, human; C491412:Pknox1 protein, mouse; D000075062:Pre-B-Cell Leukemia Transcription Factor 1; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; C083400:PBX1 protein, human; D014364:Tryptophan; D004247:DNA