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Selective photochemical treatment of oestrogen receptor in a Xenopus liver extract destroys hormone binding and transcriptional activation but not DNA binding.
Author(s) -
Cridland N.A.,
Wright C.V.,
McKenzie E.A.,
Knowland J.
Publication year - 1990
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1990.tb08311.x
Subject(s) - biology , xenopus , dna , binding site , dna binding protein , receptor , biochemistry , microbiology and biotechnology , transcription factor , gene
Photochemical excitation of a simple derivative of oestradiol using light in the UV‐A range totally, permanently and selectively inactivates the oestrogen receptor protein present in a Xenopus liver extract without affecting its overall size. Inactivation of the binding site proceeds to completion with simple, first‐order kinetics. Inactivation is prevented by excess oestradiol but not by non‐oestrogenic steroids. Using an in vitro transcription system, we show that the treatment eliminates transcription of vitellogenin genes, which are normally oestrogen‐responsive, but has no effect on the transcription of albumin genes, which are not. Native receptor binds to the two imperfectly palindromic sequences in the vitellogenin B2 gene which together constitute an oestrogen‐response unit. Its affinity for one sequence is greater than its affinity for the other, suggesting that a compulsory binding order operates when receptor interacts with the B2 gene. Photoinactivated receptor still binds to both sequences, but with reduced affinity. We also discuss our findings in the context of the current concern over the effects of UV‐A on human tissues.