ΔCH1 mutation does not affect other domains or functions of CBP and p300. (A) Western blot of CBP and p300 showing normal protein levels in CBPΔCH1/ΔCH1 and p300ΔCH1/ΔCH1 MEFs. (B, C) Immunoprecipitation/HAT assay showing that HAT activity in CBPΔCH1/ΔCH1 (B) and p300ΔCH1/ΔCH1 (C) MEFs is comparable to WT MEFs (mean±s.e.m., N=2). (D–F) Transient transfection assays showing that Gal-HIF-1α function is reduced in MEFs with multiple ΔCH1 alleles (mean±s.e.m., N=3) (D), and can be rescued by WT CBP (E, F) or p300 (F), but not by CBPΔCH1 (E) (mean±s.e.m., N=2–4). (G, H) Transactivation by factors utilizing other domains of p300 and CBP or other coactivators is unimpaired (mean±s.d., N=4).