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Updated: May 23, 2026

A High Resolution Method to Monitor Phosphorylation-dependent Activation of IRF3
Published on: January 24, 2016
Smurf1 protein negatively regulates interferon-γ signaling through promoting STAT1 protein ubiquitination and
Chao Yuan1, Jianni Qi1, Xueying Zhao1
1Key Laboratory for Experimental Teratology of the Ministry of Education and Department of Immunology, Shandong University Medical School, Jinan, Shandong 250012, China.
Abstract:
Interferons are important cytokines that mediate antiviral, antiproliferative, antitumor, and immunoregulatory activities. However, uncontrolled IFN signaling may lead to autoimmune diseases. Here we identified Smurf1 as a negative regulator for IFN-γ signaling by targeting STAT1 for ubiquitination and proteasomal degradation. Smurf1 interacted with STAT1 through the WW domains of Smurf1 and the PY motif in STAT1 and catalyzed K48-linked polyubiquitination of STAT1. Interestingly, the Smurf1-mediated ubiquitination and degradation did not require STAT1 tyrosine and serine phosphorylation. Subsequently, overexpression of Smurf1 attenuated IFN-γ-mediated STAT1 activation and antiviral immune responses, whereas knockdown of Smurf1 enhanced IFN-γ-mediated STAT1 activation, expression of STAT1 target genes, and antiviral immune responses. Furthermore, IFN-γ stimulation led to enhanced expression of Smurf1. Therefore, our results demonstrate that Smurf1 is a negative feedback regulator for IFN-γ signaling by targeting STAT1 for ubiquitination and proteasomal degradation.
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