SKP2 Activation by Thyroid Hormone Receptor β2 Bypasses Rb-Dependent Proliferation in Rb-Deficient Cells.

Germline mutations strongly predispose humans to cone precursor-derived retinoblastomas and strongly predispose mice to pituitary tumors, yet shared cell type-specific circuitry that sensitizes these different cell types to the loss of has not been defined. Here we show that the cell type-restricted thyroid hormone receptor isoform TRβ2 sensitizes to loss in both settings by antagonizing the widely expressed and tumor-suppressive TRβ1. TRβ2 promoted expression of the E3 ubiquitin ligase SKP2, a critical factor for -mutant tumors, by enabling EMI1/FBXO5-dependent inhibition of SKP2 degradation.