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Proc Natl Acad Sci U S A. 2007 Oct 23;104(43):17028-33. Epub 2007 Oct 17.

Elevated level of SUMOylated IRF-1 in tumor cells interferes with IRF-1-mediated apoptosis.

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  • 1Molecular Therapy Research Center, Sungkyunkwan University, Seoul 135-710, Korea.

Abstract

SUMOylation of transcription factors often attenuates transcription activity. This regulation of protein activity allows more diversity in the control of gene expression. Interferon regulatory factor-1 (IRF-1) was originally identified as a regulator of IFN-alpha/beta, and its expression is induced by viral infection or IFN stimulation. Accumulating evidence supports the theory that IRF-1 functions as a tumor suppressor and represses the transformed phenotype. Here we report that the level of SUMOylated IRF-1 is elevated in tumors. Site-directed mutagenesis experiments disclose that the SUMOylation sites of IRF-1 are identical to the major ubiquitination sites. Consequently, SUMOylated IRF-1 displays enhanced resistance to degradation. SUMOylation of IRF-1 attenuates its transcription activity, and SUMOylated IRF-1 inhibits apoptosis by repression of its transcriptional activity. These data support a mechanism whereby SUMOylation of IRF-1 inactivates its tumor suppressor function, which facilitates resistance to the immune response.

PMID:
17942705
[PubMed - indexed for MEDLINE]
PMCID:
PMC2040422
Free PMC Article

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