Identification of homodimerization and heterodimerization of TBLR1-RARα fusion proteins by Co-IP. The 293T cells were transfected with both Myc- and Flag-tagged TBLR1-RARα expression plasmids. (A) Homodimerization of TBLR1-RARα was detected in 293T cells by Co-IP. β-actin was used as an internal control. (B) Homodimerization could not be detected in 293T cells after treatment with 1 μM ATRA for 48 hours by Co-IP. (C) RXRα and Flag-tagged TBLR1-RARα expression plasmids were transfected into 293T cells with or without 1 μM ATRA treatment of 48 hours. Flag-tagged TBLR1-RARα could coimmunoprecipitate with RXRα (left). Heterodimers could still be detected in the presence of ATRA treatment (right). (D) Immunofluorescence analysis of 293T cells transfected with RXRα expression plasmid alone (left) or together with Flag-tagged TBLR1-RARα plasmid (right). The latter was incubated with or without 1 μM ATRA for 48 hours. Flag and RXRα antibodies were used as primary antibodies, and DAPI was used for nuclear staining. At least 100 cells were counted for colocalization analysis. Bars represent 8 μm. IB, immunoblotting; IgG, control IP with isotype antibody; Input, nonimmunoprecipitated cell lysates; IP, immunoprecipitation.