In vivo mutagenesis of the Hoxb8 hexapeptide domain leads to dominant homeotic transformations that mimic the loss-of-function mutations in genes of the Hoxb cluster.
Hox proteins are transcription factors that control developmental pathways along the anteroposterior axis of vertebrates. On their own, Hox proteins bind DNA weakly, but they gain specificity and affinity by interaction with members of the PBC subfamily of homeobox proteins. In vitro studies indicate that most of these interactions are mediated by the conserved hexapeptide motif of the Hox proteins. To study the significance of these interactions in vivo, we have generated mice that carry mutations in the Hoxb8 hexapeptide motif. Analysis of skeletal features of these mice reveals the presence of a dominant phenotype consisting of homeotic transformations, similar to those observed in mice with a loss-of-function of Hox genes, such as Hoxa7, Hoxb7, and Hoxb9. Genetic tests demonstrate that the mutations in the Hoxb8 hexapeptide motif are affecting the function of other genes located in the Hoxb cluster. The expression pattern of these genes is not affected; rather it appears that the mutant Hoxb8 protein interferes with the function of other Hox genes by binding to their targets. Our findings suggest that the homeotic transformations result from altered DNA binding specificity of the mutant Hoxb8 protein, implicating the cooperative binding between Hoxb8 hexapeptide motif and cofactors as a critical element in the fine-tuning of Hoxb8 protein target specificity. This is the first time the function of the hexapeptide domain has been evaluated in vivo in mouse development.
Medina-Martínez
Olga
O
Center for Extracellular Matrix, Institute of Biosciences and Technology, Texas A&M University, Houston, TX 77030, USA.olgamm@bcm.tmc.edu
Ramírez-Solis
Ramiro
R
D000595:Amino Acid Sequence; D000818:Animals; D019521:Body Patterning; D001842:Bone and Bones / Q000002:abnormalities; D004622:Embryo, Mammalian / Q000033:anatomy & histology / Q000502:physiology; D005260:Female; D018390:Gene Targeting; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D017403:In Situ Hybridization; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation; D010455:Peptides / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013234:Stem Cells / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014170:Transformation, Genetic
C490669:HOXB8 protein, human; C489815:HOXC8 protein, human; D018398:Homeodomain Proteins; C095822:Hoxb8 protein, mouse; C489816:Hoxc8 protein, mouse; C489576:Hoxd8 protein, mouse; D010455:Peptides; D014157:Transcription Factors; C075279:HOXD8 protein, human