Negative feedback regulation of RIG-I-mediated antiviral signaling by interferon-induced ISG15 conjugation.
RIG-I senses intracellular virus-specific nucleic acid structures and initiates an antiviral response that induces interferon (IFN) production, which, in turn, activates the transcription of RIG-I to increase RIG-I protein levels. Upon intracellular poly(I:C) stimulation, however, the levels of RIG-I protein did not correlate with the expression patterns of RIG-I transcripts. When the ISG15 conjugation system was overexpressed, ISG15 was conjugated to RIG-I and cellular levels of the unconjugated form of RIG-I decreased. The ISGylation of RIG-I reduced levels of both basal and virus-induced IFN promoter activity. Levels of unconjugated RIG-I also decreased when 26S proteasome activity was blocked by treatment with MG132, ALLN, or Lactacystin. In the presence of MG132, ISG15 conjugation to RIG-I increased, and hence, the unconjugated form of RIG-I was reduced. In Ube1L(-/-) cells, which lack the ability to conjugate ISG15, basal levels of both RIG-I protein and transcripts were increased compared to those in wild-type cells. As a result, enhanced production of ISGs and enhanced IFN promoter activity in Ube1L(-/-) cells were observed, and the phenotype was restored to that of wild-type cells by the overexpression of Ube1L. Based on these results, we propose a novel negative feedback loop which adjusts the strength of the RIG-I-mediated antiviral response and IFN production through the regulation of RIG-I protein by IFN-induced ISG15 conjugation.
Kim
Min-Jung
MJ
Department of Life Sciences, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Republic of Korea.
Hwang
Sun-Young
SY
Imaizumi
Tadaatsu
T
Yoo
Joo-Yeon
JY
D000818:Animals; D002460:Cell Line; D016207:Cytokines / Q000378:metabolism*; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism*; D025461:Feedback, Physiological; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D007372:Interferons / Q000276:immunology*; D008954:Models, Biological; D011070:Poly I-C / Q000378:metabolism; D011971:Receptors, Immunologic; D044764:Ubiquitin-Activating Enzymes / Q000235:genetics / Q000502:physiology; D014452:Ubiquitins / Q000378:metabolism*; D014780:Viruses / Q000276:immunology*
D016207:Cytokines; D011971:Receptors, Immunologic; C471538:UBA1 protein, human; D014452:Ubiquitins; C074034:ISG15 protein, human; D007372:Interferons; C452820:RIGI protein, human; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases; D044764:Ubiquitin-Activating Enzymes; D011070:Poly I-C