Figure 1.

Functional interactions between hepatitis virus B X-associated protein 2 and thyroid hormone receptor in yeast. (A) XAP2: two-hybrid experiments in yeast show T₃-dependent specific interactions of XAP2 with TRβ1 but not with TRα1 or TRβ2. ΔCterm: when the carboxy-terminal region of XAP2 is deleted, the interaction between TRβ1 and XAP2 is lost. RXR: positive control of interaction with each TR. (B) XAP2 and TRβ1 interactions in yeast depend on T₃ concentration. Plasmids expressing different Gal4 fusion proteins were used in mating. Diploids were grown with increasing doses of T₃ in selection medium. β-Galactosidase (β-Gal) activity was measured by densitometry. Each bar represents the average of two different transformants. T₃, triiodothyronine; TR, thyroid hormone receptor; TRα1, TRβ1, TRβ2, TR subtypes; XAP2, hepatitis virus B X-associated protein 2.