Fig. 1. Characterization of mice with diminished JNK activity. (A) Non-transgenic littermates and dnJNK1/2 transgenic mice from lines 22.4 and 6.1 were injected with either PBS or PE (15 mg/kg), and cardiac JNK activity was measured 30 min later using GST-cJun (1–79) as a substrate. ERK and p38 kinase activities were also measured using myelin basic protein (MBP) as the substrate after immunoprecipitation. (B) Western blot analysis with antibodies partially specific for JNK1 and JNK2 from the hearts of JNK1 null and JNK2 null mice. (C) JNK activity assay showing diminished PE-induced JNK activity in the hearts of JNK1–/–, JNK2–/– and 3-allele JNK deleted mice, yet ERK and p38 activities were unaffected. (D) Western blot analysis with a JNK3-specific antibody showed no detectable JNK3 protein in the wild-type mouse heart and no upregulation of JNK3 in either JNK1–/– or JNK2–/– hearts. Controls consisted of HEK293 cell lysate after JNK3 plasmid transfection or brain protein lysate from wild-type and JNK3 targeted mice.