Regulation of interferon regulatory factor 1[IRF1] antiviral functions by its ubiquitination

Abstract

Interferon regulatory factor 1 (IRF1) is a transcriptional factor that regulates the expression of antiviral genes. IRF1 expression is downregulated in cancer cells, which supports efficient replication of oncolytic viruses. Posttranslational modifications are one of the major cellular mechanisms that regulate IRF1 expression and functions. To understand roles of IRF1 ubiquitination on innate antiviral immunity, we determined the antiviral activity of IRF1 ubiquitin resistant mutants. IRF1 ubiquitin resistant mutants (78K, 275K, and 299K) were generated and transfected into DLD-1, DU145 or MDA-MB-468 cells. The cells were then challenged with vesicular stomatitis virus (VSV) at MOI 1. Virus infection was evaluated by Western blotting against vesicular stomatitis virus glycoprotein (VSV-G), and progeny virus production. The 275K or 299K mutants showed higher antiviral activity when compared to wild type IRF1. Conversely, cells transfected with the 78K mutant were more susceptible to VSV infection than those transfected with wild type IRF1. In conclusion, 78K, 275K, and 299K sites are IRF1 ubiquitination sites which regulate IRF1 antiviral functions.