The role of RIP140 in retinoid mediated signaling

Cell-and context-specific activities of nuclear receptors may in part be due to distinct coregulator complexes recruited to distinct subsets of target genes. RIP140 (also called NRIP1) is a ligand-dependent corepressor that is inducible with retinoic acid (RA). We have shown previously that silencing of RIP140 enhances RA-induced differentiation and enhances the induction of model RA target genes in human embryonal carcinoma cells (EC). Through use of microarray technology we sought to elucidate in a de novo fashion the global role of RIP140 in RA-dependent signaling. RIP140-dependent gene expression was largely consistent with RIP140 functioning to limit RAR signaling. Few if any genes were regulated in a manner to support a role for RIP140 in active repression. Interestingly, approximately half of the RA-dependent genes were unaffected by RIP140, suggesting that RIP140 may discriminate between different classes of RA target genes. RIP140 silencing also accelerated RA target gene activation and sensitized EC cells to low doses of RA. Together the data suggests that the RIP140-dependent RA target genes identified here may be particularly important in mediating RA-induced tumor cell differentiation. RIP140 may be an attractive target to sensitize tumor cells to retinoid-based differentiation therapy.

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Heim KC, White KA, Deng D, Tomlinson CR, Moore JH, Freemantle SJ, Spinella MJ