S. Kersten et al., RETINOID-X-RECEPTOR-ALPHA FORMS TETRAMERS IN SOLUTION, Proceedings of the National Academy of Sciences of the United Statesof America, 92(19), 1995, pp. 8645-8649
Protein-protein interactions allow the retinoid X receptor. (RXR) to b
ind to cognate DNA as a homo- or a heterodimer and to participate in m
ediating the effects of a variety of hormones on gene transcription. H
ere we report a systematic study of the oligomeric state of RXR in the
absence of a DNA template. We have used electrophoresis under nondena
turing conditions and chemical crosslinking to show that in solution,
RXR alpha forms homodimers as well as homotetramers. The dissociation
constants governing dimer and tetramer formation were estimated by flu
orescence anisotropy studies. The results indicate that RXR tetramers
are formed with a high affinity and that at protein concentrations hig
her than about 70 nM, tetramers will constitute the predominant specie
s; Tetramer formation may provide an additional level of the regulatio
n of gene transcription mediated by RXRs.