ASC-2 is a key adaptor for RAR-dependent recruitment of MLL3 and MLL4s. (A) HEK293 cells were transfected with siRNA against MLL3 or MLL4s, along with CMV-GFP. These cells were immunostained for MLL3, MLL4s, and ASC-2, 3 days posttransfection. GFP-positive cells (i.e., transfected cells; arrows) were monitored for the expression of MLL3, MLL4s, and ASC-2. (B) HEK293 cells were transfected with control siRNA, siRNA against MLL3 or MLL4s, or siRNAs for both MLL3 and MLL4s. Two days posttransfection, cells were treated with vehicle or 0.1 μM 9-cis-RA (9-RA) for 12 h, and they were then tested for RAR-β2 transcript levels by Q-PCR. (C) Nuclear extracts of HeLa cells were subjected to immunoprecipitations (IP) with IgG and ASC-2 antibody followed by immunoblotting with ASC-2 and WDR5 antibodies. (D) HEK293 cells were transfected with control (con) siRNA or siRNA against WDR5 or RbBP5. Two days posttransfection, cells were treated with vehicle or 0.1 μM 9-cis-RA for 12 h and tested for RAR-β2 and GAPDH (control; data not shown) transcripts by Q-PCR. (E) Immortalized cell lines from wild-type (wt) and ASC-2−/− MEFs were treated with 0.1 μM 9-cis-RA for 0–45 min and subjected to ChIPs with antibodies against MLL3 and MLL4s.