Fig. 3. MAK is an activator of JNK. JNK activity was analyzed in embryonic lysates by in vitro phosphorylation of GST-Jun(1-135). Four-cell embryos were injected marginally four times with GFP, MAK or MAK-KD RNA (1.5 ng per injection), or N-Fz8 RNA (0.5 ng per injection) as a positive control. Lysates were collected at stage 14 for JNK activity determination by western analysis with anti-phospho-Jun antibodies. Assays were carried out in duplicates, with 10 embryos in each experimental group. Anti-GST and anti-ß-tubulin antibodies indicate loading.