Dominant Negative Mutant of Retinoic Acid Receptorα Inhibits Retinoic Acid-Induced P19 Cell Differentiation by Binding to DNA

Abstract

Retinoic acid (RA) is a potent inducer of P19 cell differentiation. RA activity is thought to be mediated by nuclear RA receptors (RARs), transcription factors whose activity is dependent on RA. There are three RARs called α, β, and γ. We created truncated versions of the three RARs and compared their activities as inhibitors of RA-mediated gene transcription and of P19 cell differentiation. Only mutants of the RARα were inhibitory in these assays. A mutant of RARα carrying a 10-amino-acid insert was able to heterodimerize with RXRβ or with the normal RARα and the inhibitory activity of this mutant was dependent on an intact DNA binding domain. We conclude that dominant negative mutants of RARα act by heterodimerizing with RXRs or RARs and binding to RA response elements on DNA, thereby preventing binding of the normal receptors to those sites.