Assuntos
Proteínas de Homeodomínio/metabolismo , Proteínas de Homeodomínio/fisiologia , Leucemia/etiologia , Leucemia/metabolismo , Proteínas de Fusão Oncogênica/metabolismo , Proteínas de Fusão Oncogênica/fisiologia , Translocação Genética , Animais , Sítios de Ligação , Diferenciação Celular , Dimerização , Heterozigoto , Proteínas de Homeodomínio/genética , Humanos , Leucemia/genética , Linfócitos/citologia , Camundongos , Modelos Genéticos , Mutação , Proteínas de Fusão Oncogênica/genética , Ligação Proteica , Fatores de Transcrição/química , Ativação TranscricionalRESUMO
We have shown that the 26 bp bx1 element from the regulatory region of Distal-less is capable of imposing control by the homeotic genes Ultrabithorax and abdominal-A on a general epidermal activator in Drosophila. This provides us with an assay to analyze the sequence requirements for specific repression by these Hox genes. Both the core Hox binding site, 5'-TAAT, and the adjacent EXD 5'-TGAT core site are required for repression by Ultrabithorax and abdominal-A. The Distal-less bx1 site thus fits with the model of Hox protein binding specificity based on the consensus PBX/HOX-family site TGATNNAT[g/t][g/a], where the key elements of binding specificity are proposed to lie in the two base pairs following the TGAT. A single base pair deletion in the bx1 sequence generates a site, bx1:A(-)mut, that on the consensus PBX/HOX model would be expected to be regulated by the Deformed Hox gene. We observed, however, that the bx1:A(-)mut site was regulated predominantly by Sex combs reduced, Ultrabithorax and abdominal-A. The analysis of this site indicates that the specificity of action of Hox proteins may depend not only on selective DNA binding but also on specific post-binding interactions.
Assuntos
Proteínas de Ligação a DNA/metabolismo , Proteínas de Drosophila , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Proteínas de Insetos/metabolismo , Proteínas Nucleares , Proteínas Repressoras/metabolismo , Elementos de Resposta , Animais , Proteínas de Ligação a DNA/genética , Drosophila/embriologia , Proteínas de Homeodomínio/fisiologia , Proteínas de Insetos/genética , Proteínas Repressoras/genética , Fatores de Transcrição/genética , Fatores de Transcrição/fisiologiaRESUMO
The extradenticle protein is a homeodomain transcription factor which has an important role regulating the DNA-binding specificity of homeotic selector proteins. We have made a monoclonal antibody against extradenticle and have studied the expression of the protein in the embryo and in imaginal discs. We find that extradenticle is initially uniformly distributed as expected but strikingly is excluded from nuclei until gastrulation. During the extended germ band stage the protein remains predominantly cytoplasmic and does not accumulate in nuclei until germ band retraction. Nuclear accumulation occurs in a highly spatially regulated pattern. In the imaginal discs the nuclear accumulation of extradenticle is also spatially regulated and, in the wing and leg discs, distal regions exhibit cytoplasmic extradenticle whereas proximally the protein is nuclear. We suggest that this regulation of the sub-cellular localisation of extradenticle is important for the interactions between extradenticle and the homeotic selector proteins and that extradenticle is not simply a ubiquitously available cofactor.
