Localization of transcriptional co-activator CBP in the ameloblasts and the other enamel organ-derived cells of the rat incisor.

CREB-binding protein (CBP) was examined in ameloblasts and in other enamel organ-derived cells of the rat incisor, using Western blotting analysis and immunocytochemistry by specific antibodies. Western blotting of labial tissues, including ameloblasts of the incisors, detected a single band with a molecular weight equivalent to the reported value of CBP. In immunocytochemistry, CBP was localized in ameloblast nuclei in the maturation zone but not in the secretion and transition zones. The nuclei of the other enamel organ-derived cells were also positive. Because this protein is suggested to take part in c-Jun-mediated transcription, the present study and the results of a previous report showing c-Jun localization in the nuclei of enamel organ-derived cells suggest that the enamel organ-derived cells, including maturation ameloblasts, undergo active transcriptional regulation.