Flag-EGFP and -Vret-L WT and mutants were immunoprecipitated using the anti-Flag antibody and then western blotting was performed using anti-Flag, anti-Siwi, anti-Ago3 and anti-Vret antibodies. The domain structures of Tud1mut (Y753A/Y757A/N759A) and Tud2mut (Y973A/ Y976A/N978A) are shown. 