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

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 X 10(-10) M.