The DBP transcriptional activation domain is highly homologous to that of HLF and TEF and is not responsible for the tissue type-specific transcriptional activity of DBP

DBP, HLF and TEF comprise a distinct subfamily of mammalian bZIP proteins t hat plays an important role in regulation of tissue-specific gene expressio n, particularly in the liver. In this report we demonstrate that DBP contai ns a 38 amino acid TAD which is highly homologous to the HLF and TEF TADs t hat we have delineated previously. Deletion of this domain completely abrog ates transcriptional activity of native DBP and GAL4-DBP fusion proteins. T his domain functions as a modular TAD that is a potent transcriptional acti vator when fused to the GAL3 DBD. While DBP itself is a liver-specific tran sactivator, the DBP TAD is active in a variety of cell types, indicating th at liver-specific activity is not an intrinsic property of the TAD and must be conferred by other regions of the protein. Using GAL4-HLF fusion protei ns, we further refine the core TAD of PAR proteins to a region of 13 amino acids. Recently described PAR-bZIP proteins from Drosophila and zebrafish a lso contain domains that share strong homology with the TAD of mammalian PA R proteins, making this one of the most highly evolutionarily conserved TAD s identified to date. (C) 2001 Elsevier Science B.V. All rights reserved.