Ligand-bound receptors undergo conformational changes resulting in loss of bound repressors and re-positioning of helix12 which can now fit the the LxxxLL motif of coactivators. The coactivators also act as adapters to recruit other protein complexes. For more details check PMIDs 19471584 and 17320364. The three coactivators are listed with aliases in parentheses, full names and links to gene report pages:

Ncoa1 (Src-1, Rip160) – nuclear receptor coactivator 1
Ncoa2 (Tif2, Src2) – nuclear receptor coactivator 2
Ncoa3 (Aib3, Src3, Aib-1) – nuclear receptor coactivator 3