IDENTIFICATION OF NUCLEAR PROTEINS INTERACTING WITH THE LIVER-SPECIFIC ENHANCER B-ELEMENT OF THE ANTIFREEZE PROTEIN GENE IN WINTER FLOUNDER

The intron of the winter flounder antifreeze protein (AFP) gene contai ns a liver-specific enhancer element B as demonstrated by transient ex pression in mammalian cells. Element B interacts with rat C/EBP alpha and a novel protein, tentatively designated as the antifreeze enhancer -binding protein (AEP). Present studies revealed that nuclear proteins from the winter flounder liver interact similarly and specifically to element B as shown by footprinting analysis and gel retardation assay s. The presence of C/EBP in the flounder liver was confirmed by Wester n blot analysis. In vitro transcription assays in its homologous syste m further demonstrated the transactivation activity of the AFP gene in tron. The present findings suggest that the mechanisms for regulating liver-specific transcription are evolutionarily conserved.