Estradiol‐dependent trans‐acting factor binds preferentially to a dyad‐symmetry structure within the third intron of the avian vitellogenin gene

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Abstract
The secondary activation of the avian vitellogenin II gene in isolated liver nuclei by cytoplasmatic liver extracts of estradiol‐treated chicks is accompanied by the binding of a protein from the extract to the structural part of the cloned gene. Both the DNA‐binding and gene‐stimulatory activities, which cochromatograph on heparin‐Sepharose, are apparently present only in the cytoplasmatic liver extracts of estradiol‐treated roosters and in the oviduct extracts of egg‐laying hens. DNA‐binding competition assays combined with exonuclease III footprinting showed that the factor binds to the imperfect dyad‐symmetry structure 5‘GTCTTGTTCCAAAC3’ within the third intron of the gene. The factor is sequence specific and binds equally well to both single‐ and double‐stranded DNA with an estimated dissociation constant of 3.5 × 10−10M.