title: Brachyury and related Tbx proteins interact with the Mixl1 homeodomain protein and negatively regulate Mixl1 transcriptional activity.
abstract: Mixl1 is a homeodomain transcription factor required for mesoderm and endoderm patterning during mammalian embryogenesis. Despite its crucial function in development, co-factors that modulate the activity of Mixl1 remain poorly defined. Here we report that Mixl1 interacts physically and functionally with the T-box protein Brachyury and related members of the T-box family of transcription factors. Transcriptional and protein analyses demonstrated overlapping expression of Mixl1 and Brachyury during embryonic stem cell differentiation. In vitro protein interaction studies showed that the Mixl1 with Brachyury associated via their DNA-binding domains and gel shift assays revealed that the Brachyury T-box domain bound to Mixl1-DNA complexes. Furthermore, luciferase reporter experiments indicated that association of Mixl1 with Brachyury and related T-box factors inhibited the transactivating potential of Mixl1 on the Gsc and Pdgfrα promoters. Our results indicate that the activity of Mixl1 can be modulated by protein-protein interactions and that T-box factors can function as negative regulators of Mixl1 activity.
authors.affiliation: Differentiation and Transcription Laboratory, Peter MacCallum Cancer Centre and the Pathology Department, The University of Melbourne, Melbourne, Victoria, Australia.
authors.forename: Lloyd A
authors.initials: LA
authors.lastname: Pereira
authors.forename: Michael S
authors.initials: MS
authors.lastname: Wong
authors.forename: Sue Mei
authors.initials: SM
authors.lastname: Lim
authors.forename: Alexandra
authors.initials: A
authors.lastname: Sides
authors.forename: Edouard G
authors.initials: EG
authors.lastname: Stanley
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Elefanty
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D005326:Fetal Proteins / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D018398:Homeodomain Proteins / Q000378:metabolism*; D006801:Humans; D051379:Mice; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D025941:Protein Interaction Mapping; D020825:T-Box Domain Proteins / Q000378:metabolism*; D014158:Transcription, Genetic; D000098908:Brachyury Protein
chemical_list: D005326:Fetal Proteins; D018398:Homeodomain Proteins; D020825:T-Box Domain Proteins; D000098908:Brachyury Protein; C499230:MIXL1 protein, human; C108625:TBX1 protein, human