RETINOBLASTOMA CONTROL ELEMENT-BINDING PROTEINS ARE INDUCED DURING IN-VIVO TERMINAL DIFFERENTIATION OF THE LIVER AND BIND TO THE DBP PROMOTER

Growth regulation of terminal differentiation was studied by analysis of the promoter of the transcription factor D-site binding protein (DBP) using nuclear extracts from rat liver undergoing regeneration or from normal liver early in development. Four proximal binding sites for nuclear proteins were identified, three of which showed significant quantitative or qualititive changes in associated factors upon growth induction. Two of these sites bound factors common to the retinoblastoma control element and these proteins were induced upon terminal differentiation of the liver. These factors were also rapidly down-regulated upon induction of regenerative growth and consequent dedifferentiation. These results provide a link between the regulation of growth and differentiation in an in vivo model system.