title: Multiple Pit-1-binding sites facilitate estrogen responsiveness of the prolactin gene.
abstract: Previous studies have shown that estrogen responsiveness of the rat PRL gene requires the presence of both the estrogen receptor and the tissue-specific transcription factor, Pit-1. To examine the contribution of individual Pit-1-binding sites in permitting an estrogen response, we mutated specific sites in both the proximal and distal regions of the rat PRL gene. The studies reveal that mutation of Pit-1-binding sites in either the proximal or the distal region can have an effect on estrogen responsiveness. The most important Pit-1-binding site appears to be the site in the distal enhancer, which is adjacent to the estrogen receptor-binding site. However, mutation of combinations of other Pit-1-binding sites reveals that these sites also contribute to the estrogen response of the PRL gene. The binding sequences for another transcription factor cannot substitute for Pit-1 sites in bringing about a wild-type estrogen response, as shown by replacement of Pit-1-binding sites with a consensus cAMP-responsive element. Conversion of the imperfect palindromic estrogen response element of the PRL gene to a perfect palindrome eliminated the positive effects of an intact 1D Pit-1-binding site. To examine potential physical interactions between the estrogen receptor and Pit-1, a protein interaction assay was performed. The results demonstrate that labeled estrogen receptor can bind to Pit-1 immobilized on glutathione agarose beads. However, most of the interaction between Pit-1 and the estrogen receptor appears to be DNA dependent.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Cell Biology and Anatomy, Oregon Health Sciences University, Portland 97201.
authors.forename: B E
authors.initials: BE
authors.lastname: Nowakowski
authors.forename: R A
authors.initials: RA
authors.lastname: Maurer
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D016384:Consensus Sequence; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D004967:Estrogens / Q000494:pharmacology*; D017930:Genes, Reporter; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010911:Pituitary Neoplasms; D017354:Point Mutation; D011388:Prolactin / Q000235:genetics*; D051381:Rats; D012091:Repetitive Sequences, Nucleic Acid; D050817:Transcription Factor Pit-1; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D004967:Estrogens; C494186:Pou1f1 protein, rat; D050817:Transcription Factor Pit-1; D014157:Transcription Factors; D011388:Prolactin; D004247:DNA