Structural features of thyroid hormone response elements that increase susceptibility to inhibition by an RTH mutant thyroid hormone receptor.
The chicken lysozyme silencer F2 (F2) thyroid hormone response element (TRE) contains an unusual everted palindromic arrangement, has a high affinity for thyroid hormone receptor (TR) homodimers, and is especially sensitive to dominant negative inhibition by, the T3 resistance (RTH) mutant TR beta P453H. We used various TREs and TR mutations to determine the mechanisms for this sensitivity. Changing the F2 orientation from an everted palindrome to a direct repeat with a 4-bp gap (DR+4) (F2-DR) decreased the sensitivity to inhibition at high T3 concentrations, while a loss of this sensitivity occurred with a palindromic arrangement of these same half-sites. F2 contains the dinucleotide TG 5' to each consensus half-site conforming to the optimal TR-binding octamer, YRRGGTCA. A T to A change in position 1 of both F2 half-sites markedly reduced T3-induction, yet only slightly reduced TR homodimer or TR-retinoid X receptor (RXR) heterodimer binding. The TR beta ninth heptad mutation, L428R, prevents TR heterodimerization with RXR and eliminates the inhibitory effect of the P453H mutant TR on the F2-DR, but not the F2 element. Structural features of a TRE that favor strong TR binding of both TR homodimers and TR-RXR heterodimers containing the mutant TR, such as the everted palindromic conformation or the optimal TR-binding consensus octamer, enhance the sensitivity of a TRE to inhibition by the mutant TR. Thus, both half-site orientation and sequence contribute to the sensitivity of a given TRE to dominant negative inhibition by a mutant TR.
Zavacki
A M
AM
Program in Biological and Biomedical Sciences, Thyroid Division, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
Harney
J W
JW
Brent
G A
GA
Larsen
P R
PR
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D002645:Chickens; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis; D016384:Consensus Sequence; D004351:Drug Resistance; D015321:Gene Rearrangement; D013006:Growth Hormone / Q000096:biosynthesis; D006801:Humans; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D051381:Rats; D011988:Receptors, Thyroid Hormone / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D012045:Regulatory Sequences, Nucleic Acid; D012091:Repetitive Sequences, Nucleic Acid; D014162:Transfection; D014284:Triiodothyronine / Q000494:pharmacology*
D046911:Macromolecular Substances; D011988:Receptors, Thyroid Hormone; D011994:Recombinant Proteins; D014284:Triiodothyronine; D013006:Growth Hormone; D015500:Chloramphenicol O-Acetyltransferase