Differential binding and activation of thyroid hormone response elements by TR alpha 1 and RXR alpha-trap heterodimers.
Thyroid hormone receptor (TR) forms homo- and heterodimers on various thyroid hormone response elements (TREs). We wished to clarify the relationship of homo- and heterodimer binding to TREs and their trans-activation. We investigated binding characteristics in gel mobility shift assays using synthetic direct repeat (DR) TREs having the consensus motifs separated by different oligonucleotide gaps, and we compared binding to trans-activation mediated via the direct repeat TRE. HTR alpha 1 purified from E. coli formed a monomer and homodimer on DR-TRE +0 to +5 but binding did not closely correlate with T3-dependent trans-activation. When RXR alpha expressed in COS 1 cell was added to purified TR alpha 1 in the gel shift assays, TR/RXR heterodimers were formed, and binding of heterodimers correlated highly with the level of trans-activation. These results strongly suggest that TR/TRAP heterodimers mediate the effect of thyroid hormone on DR-TREs. We also found T3-dependent disruption of homodimer formation on DR +0 to +2 and that T3 increased heterodimer formation on these TREs.
Miyamoto
T
T
Department of Medicine, University of Chicago, IL 60637.
Suzuki
S
S
DeGroot
L J
LJ
D001483:Base Sequence; D016384:Consensus Sequence; D004926:Escherichia coli / Q000235:genetics; D008969:Molecular Sequence Data; D010957:Plasmids; D011988:Receptors, Thyroid Hormone / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012091:Repetitive Sequences, Nucleic Acid; D017422:Sequence Analysis, DNA; D015533:Transcriptional Activation; D014162:Transfection
D011988:Receptors, Thyroid Hormone