Potent transactivation domains of the Ah receptor and the Ah receptor nuclear translocator map to their carboxyl termini.
The Ah receptor (AHR) is a ligand-activated transcription factor that is structurally related to its dimerization partner, the Ah receptor nuclear translocator (ARNT), and two Drosophila proteins, SIM and PER. All four proteins contain a region of homology now referred to as a PAS homology domain. In addition, the AHR, ARNT, and SIM harbor a basic region helix-loop-helix motif in their N termini, whereas PER does not. Previous mapping studies of the AHR have demonstrated that the PAS domain contains sequences required for ligand recognition, dimerization, and interaction with the 90-kDa heat shock protein. They also have confirmed that the basic region helix-loop-helix domain plays a role in both dimerization and sequence-specific DNA binding. To identify domains involved in transactivation of target genes, we generated chimeras of AHR/ARNT deletion mutants with the DNA binding region of the yeast Gal4 protein, transiently expressed these in COS-1 cells, and monitored their capacity to activate the chloramphenicol acetyltransferase reporter gene under the control of a minimal promoter driven by enhancer elements recognized by Gal4. Extensive analysis of these fusions revealed that the AHR and ARNT harbor potent transactivation domains within their C termini. Importantly, the amino-terminal halves of both the AHR and ARNT were found to be devoid of transactivation activity.
Jain
S
S
Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, Chicago, Illinois 60611.
Dolwick
K M
KM
Schmidt
J V
JV
Bradfield
C A
CA
D000595:Amino Acid Sequence; D000818:Animals; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D001483:Base Sequence; D002460:Cell Line; D002522:Chlorocebus aethiops; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins; D005786:Gene Expression Regulation; D066298:In Vitro Techniques; D051379:Mice; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D018336:Receptors, Aryl Hydrocarbon / Q000737:chemistry*; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D013329:Structure-Activity Relationship; D015534:Trans-Activators / Q000737:chemistry*; D014157:Transcription Factors / Q000737:chemistry*
C497397:Arnt protein, mouse; D004268:DNA-Binding Proteins; D009838:Oligodeoxyribonucleotides; D018336:Receptors, Aryl Hydrocarbon; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator