Rescue of MLL-fusion–immortalized KSL cells from Plzf depletion by transduction with shRNA-resistant Plzf, but not with a resistant Plzf lacking the BTB/POZ domain. (A) Expression levels of Plzf by QRT-PCR (upper) and relative CFU (lower) of the cells sorted from shRNA-transduced immortalized cells in colony forming assays. WT whole KSL and MP cells immortalized by retroviral transduction of MLL-ENL, MLL-SEPT6, or E2A-HLF were harvested at the end of the first plating. (B) Structures of Plzf and a mutant lacking the BTB/POZ domain, modified with introduction of silent mutations (*) resistant to shRNA (shP01) against Plzf. Arrows indicate primers to detect Plzf transcripts in the coding region. (C) Expression levels of the mutated Plzf by QRT-PCR in the MLL-ENL–immortalized WT KSL (ME) cells retrovirally transduced with Plzf* (ME+Plzf*) or Plzf*^/ΔBTB (ME+Plzf*^/ΔBTB). (D-E) Expression levels of Plzf by QRT-PCR (D) and relative CFU (E) of the cells sorted from shRNA-transduced ME+Plzf* or ME+Plzf*^/ΔBTB cells in colony replating assays. QRT-PCR analyses were performed using primers in the coding region (A [upper], C,D [upper]) or the 3′ untranslated region (D [lower]). The bar graphs show the mean ± SD of 3 independent experiments.