PIASy Inhibits Virus-induced and Interferon-stimulated Transcription through Distinct Mechanisms

Toru Kubota,Mayumi Matsuoka,Songxiao Xu,Noriyuki Otsuki,Makoto Takeda,Atsushi Kato,Keiko Ozato

doi:10.1074/jbc.m110.195255

Abstract

The protein inhibitor of activated STAT (PIAS) family proteins regulates innate immune responses by controlling transcription induced by Toll-like receptor, RIG-I-like receptor signaling, and JAK/STAT pathways. Here, we show that PIASy negatively regulates type I interferon (IFN) transcription. Virus infection led to enhanced type I IFN induction in PIASy null cells, and conversely PIASy overexpression reduced IFN transcription. A mutation in the LXXLL motif of the SAP domain abolished inhibition of IFN-stimulated gene expression but did not affect virus or Toll-like receptor/RIG-I-like receptor-stimulated IFN transcription, indicating that PIASy employs distinct mechanisms to inhibit virus-induced and IFN-stimulated transcription. SUMO E3 activity was not required for PIASy inhibition of IFN transcription; however, PIASy relied on the SUMO modification mechanism to inhibit IFN transcription, because the activity of the SUMO-interacting motif was required for inhibition, and knockdown of SUMO E2 enzyme UBC9 decreased inhibitory activity of PIASy. Our results demonstrate that PIASy negatively regulates both IFN transcription and IFN-stimulated gene expression through multiple mechanisms utilizing the function of different domains.

Highlights

Infection of RNA viruses is recognized by two classes of pathogen recognition receptors, Toll-like receptors (TLR)3 and RIG-I-like receptors (RLR), both of which bind viral RNAs [1,2,3,4,5,6,7]
PIASy Negatively Regulates Virus-induced Type I IFN Expression—To investigate whether PIASy is involved in the regulation of virus-induced type I IFN production, PIASyϪ/Ϫ and PIASyϩ/ϩ MEFs were infected by vesicular stomatitis virus (VSV) or EMCV
We investigated the contribution of PIASy to the regulation of type I IFN transcription

Summary

Introduction

Infection of RNA viruses is recognized by two classes of pathogen recognition receptors, Toll-like receptors (TLR)3 and RIG-I-like receptors (RLR), both of which bind viral RNAs [1,2,3,4,5,6,7]. Inhibition of Virus-induced Signaling by PIASy tion factors required for activation of the type I IFN promoter. These results indicate that PIASyϪ/Ϫ cells are more resistant to Sendai virus infection, presumably due to greater production of type I IFNs. PIASy Inhibits Type I IFN Promoter Activity Stimulated by the Activated Form of IRF3 and IRF7—Recognition of viral RNA by RIG-I leads to the activation of downstream signaling molecules such as VISA, TBK1, IKK⑀, IRF3, and IRF7 [5, 6, 43, 44].

Results

Conclusion