INTERACTION OF NUCLEAR FACTORS WITH THE CAMP RESPONSE ELEMENTS OF THEHUMAN BETA(3)-ADRENOCEPTOR GENE

Four potential cyclic adenosine 3',5'-monophosphate (cAMP) response el ements (CREs), each having at most two mismatches from the classical c anonical sequence, have been identified in the 5'UTR of the human beta (3)-adrenoceptor gene by Liggett and Schwinn (1991). Recently, three o f these CREs were shown to confer responsiveness to cAMP when cloned i nto a CAT reporter vector (Thomas et al., 1992). In this study, in vit ro gel-retardation assays have shown that recombinant human CRE bindin g protein-1 (CREB-1) or activating transcription factor-1 (ATF-1) can interact specifically with these four putative CREs (termed beta(3)CRE 1-4), although with different affinities. Nuclear extracts from human brown or white adipose tissue contain proteins interacting with beta(3 )CRE3 and beta(3)CRE2. These adipose nuclear factors were shown by com petition assays and the use of antibodies to differ from CREB-1 or ATF -1. The nuclear factor(s) interacting with beta(3)CRE2 was found in hu man and rat brown and white adipose tissues, but not in the other nona dipose tissues examined, i.e., rat lung, liver, kidney, and heart, sug gesting an adipose tissue-specific DNA binding or expression pattern. beta(3)CRE2 is found to constitute a hexameric element that is highly homologous to the binding site for members of the nuclear hormone rece ptor superfamily, and a competition assay using this site has provided evidence that an adipose tissue-specific orphan member of this superf amily may bind to beta(3)CRE2. Reporter gene assays have indicated tha t beta(3)CRE2 and beta(3)CRE3 slightly repress the basal level of tran scription and that beta(3)CRE2 confers cAMP responsiveness, whereas be ta(3)CRE3 does not.