RETINOIC ACID-RESPONSE ELEMENTS WITH A HIGHLY REPETITIVE STRUCTURE ISOLATED BY IMMUNO-SELECTION FROM GENOMIC DNA

In vitro binding sites of retinoic acid receptors (RARs) were isolated from mouse genomic DNA by immunoprecipitation of receptor/DNA complex es. PuG(G/T)TCA half-site motifs, which constitute RA-responsive eleme nts (RAREs), were identified in the immunoselected fragments (ISFs), s ome of which contained highly repetitive arrangements of this motif. G enomic Southern analysis of a number of ISFs showed them to be of a si ngle or low copy number. Several, but not all. ISFs acted as ligand-de pendent RAREs in transient transfection assays. Two ISFs with repetiti ve RARE motifs responded preferentially to 9-cis retinoic acid-ligande d retinoid X receptor in the presence or absence of co-transfected RAR , while little activation was seen with RAR alone in the presence of e ither all-trans or 9-cis retinoic acid. Another ISF, containing consen sus TATA and CAAT box motifs, was shown to have RA-inducible promoter activity. The results suggest a high degree of promiscuity in response element recognition by retinoid receptors.