PIASy represses TRIF-induced ISRE and NF-kappaB activation but not apoptosis.

The TIR domain-containing adapter protein TRIP is critically involved in TLR3-induced IFN-beta production through activation of NF-kappaB and ISRE. In addition, TRIF also induces apoptosis when overexpressed in 293 cells. In this report, we demonstrate that PIASy, a member of the PIAS SUMO-ligase family, interacts with TRIP, IRF-3 and IRF-7. In reporter gene assays, PIASy dramatically inhibits TRIF-induced NF-kappaB, ISRE and IFN-beta activation but not TRIF-induced apoptosis. Furthermore, PIASy also inhibits IRF-3, IRF-7 and Sendai virus-induced ISRE activation. Our results suggest that PIASy is an inhibitor of TRIF-induced ISRE and NF-kappaB activation but not apoptosis.