RAF1 and infection: Accordingly, expressing a dominant negative form of the upstream MAPKKK, Raf, in ECs also decreased upd3-lacZ regulation by infection, while blocking other MAPKKKs, TGF-β activated kinase 1 (TAK1), Apoptotic signal-regulating kinase 1 (ASK1) and MEKK1, did not (Fig 6A and S8D Fig).