CBP and histone deacetylase inhibition enhance the transactivation potential of the HOXB7 homeodomain-containing protein

Homeodomain-containing proteins are transcription factors regulating the co ordinated expression of multiple target genes involved in development, diff erentiation and cellular transformation. In this study, we demonstrated tha t HOXB7, one member of this family, behaved as a transactivator in breast c ancer cells. Deletion of either the HOXB7 N-terminal domain or the C-termin al acidic tail abolished this transcriptional effect, suggesting a combinat ion of distinct functional transactivating domains. HOXB7 physically intera cted both in vitro and in vivo with the coactivator CREB-binding protein (C BP). This interaction led to an enhanced transactivating potential and requ ired the N-terminal of HOXB7 as well as two domains located at the C-termin al part of CBP. Moreover, trichostatin A, a deacetylase inhibitor, strongly enhanced the transcriptional properties of HOXB7. Our data therefore indic ate that HOX proteins can directly interact with CBP and that acetylation/d eacetylation may regulate their transcriptional properties.