Hox repression of a target gene: extradenticle-independent, additive action through multiple monomer binding sites.

摘要: Homeotic (Hox) genes regulate the identity of structures along anterior-posterior axis most animals. The low DNA-binding specificities Hox proteins have raised question how these transcription factors selectively target gene expression. discovery that Extradenticle (Exd)/Pbx and Homothorax (Hth)/Meis act as cofactors for several has advanced view interactions with are critical to selectivity proteins. It is not clear, however, what extent also in absence cofactors. In Drosophila melanogaster, protein Ultrabithorax (Ubx) promotes haltere development suppresses wing by repressing many wing-patterning hierarchy, this activity requires neither Exd nor Hth function. Here, we show Ubx directly regulates a flight appendage-specific cis-regulatory element spalt (sal) gene. We find multiple monomer Ubx-binding sites required completely repress cis-element haltere, individual sufficient mediate its partial repression. These results suggest can cofactor Extradenticle. propose regulation some evolves via accumulation binding sites. Furthermore, because morphological diversity distal parts arthropod vertebrate appendages involve Hox, but Exd/Pbx or Hth/Meis proteins, mode appears be important appendage evolution diversity.