| As examined by in situ hybridization , steroid receptor coactivator ( SRC ) 2 , SRC 3 , PPAR interacting protein , receptor interacting protein 140 ( RIP 140 ) , nuclear receptor corepressor ( N CoR ) , and silencing mediator for retinoid and thyroid hormone receptor ( SMRT ) exhibit overlapping expression with that of PPARdelta in the periimplantation mouse uterus . ^^^ Glutathione S transferase ( GST ) pull down assays show that PPARdelta physically interacts with SRC 1 3 , RIP 140 , PPAR binding protein , N CoR , and SMRT in the absence of ligands , suggesting their potent interactions with PPARdelta . ^^^ Transient transfection assays in AN ( 3 ) CA cells show that among members of the SRC family , only SRC 2 serves as a true coactivator for PPARdelta , whereas all SRC members could enhance PPARalpha induced transcriptional activation . ^^^ Collectively , the results suggest that gene regulation by PPARdelta in the uterine cells uniquely responds to SRC 2 , N CoR , SMRT , or RIP 140 , and these interactions may be operative during implantation when these cofactors are abundantly expressed . . ^^^ |