Thyroid hormone receptors (TRs), expressed as TR1, TR1 and TR2 isoforms, are members of the steroid hormone nuclear receptor gene superfamily which are ligand-dependent transcription factors. The TR isoforms differ primarily in their N-terminal (A/B) domains suggesting that the A/B regions mediate distinct transcriptional activation functions in a cell type dependent or promoter specific fashion. The nuclear receptor ligand binding domain (LBD) undergoes a conformational change upon ligand binding that results in the recruitment of co-activators to the LBD. For glucocorticoid receptor (GR) and estrogen receptor- (ER), the same co-activator can contact both the LBD and A/B domains, thus leading to enhanced transcriptional activation. Very little is known regarding the role of A/B domains of the TR isoforms. The A/B domain of TR2 exhibits higher ligand-independent transcriptional activity than the A/B regions of TR1 or TR1. Thus, we examined the role of the A/B domain and the LBD of rat TR2 in integrating the transcriptional activation function of the A/B and LBD domains by different co-activators. Both domains are essential for a productive functional interaction with CBP and we found that CBP binds to the A/B domain of TR2 in vitro. In contrast, SRC-1a interacts strongly with the LBD but not the A/B domain. The co-activator NRC interacts primarily with the LBD, although a weak interaction with the A/B domain further enhances ligand-dependent binding with TR2. Our studies document the interplay between the A/B domain and the LBD of TR2 in recruiting different co-activators to the receptor. Since NRC and SRC-1a bind CBP, and CBP enhances ligand-dependent activity, our studies suggest a model where co-activator recruitment of NRC (or SRC-1a) occurs primarily through the LBD while the complex is further stabilized through an interaction of CBP with N-terminus of TR2.