RAG down-regulation and chromatin hub disassembly requires Ikaros. (A) Rag1 transcript abundance evaluated by RT-PCR in control and PMA plus ionomycin (P+I)–treated wild-type, Rag1p Ikaros site mutant, or Ikzf1 KO VL3-3M2 cells. The data represent mean ± SEM of five independent experiments. (B) Rag2 transcript abundance evaluated as in A in control and PMA plus ionomycin–treated wild-type and Ikzf1 KO VL3-3M2 cells. The data represent mean ± SEM of five independent experiments. (C) 3C analysis of interactions of BglII fragments with the ASE viewpoint in control and PMA plus ionomycin–treated wild-type (left) and Ikzf1 KO (right) VL3-3M2 cells. The data represent the mean ± SEM of three independent experiments, with interaction frequencies normalized to those of a nearest neighbor BglII fragment. *, P < 0.05; **, P < 0.01; ***, P < 0.001, ****, P < 0.0001 by two-way ANOVA with Holm-Sidak’s multiple comparisons test.