passages.id: split_4_test_222_passage
passages.type: progene_text
passages.text: We therefore hypothesize either that : (i) these mutants might be able to heterodimerize with a protein other than RXR and the affinity for this novel partner may depend on the nature of the PPRE and to some degree on the choice of the activator , or alternatively ; (ii) that additional nuclear proteins might compensate in vivo for the decreased binding of RXR to these mutant PPARs observed in vitro .