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X-ray crystal structure of IRF-3 and its functional implications
Kiyohiro Takahasi1, Nobuo N Suzuki, Masataka Horiuchi
1Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita 12 Nishi 6, Kita-ku, Sapporo 060-0812, Japan.
Nature Structural Biology
|October 14, 2003
Summary
Interferon regulatory factor 3 (IRF-3) dimerization, triggered by phosphorylation, creates a binding site for p300/CBP. This structural insight reveals IRF-3’s evolutionary link to Smad signaling pathways in innate immunity regulation.
Area of Science:
- Immunology
- Structural Biology
- Molecular Biology
Background:
- Interferon regulatory factor 3 (IRF-3) is a key transcription factor in innate immunity, activated by Toll-like receptor (TLR) signaling.
- Post-translational modifications, including phosphorylation, are crucial for IRF-3 activation and function.
Purpose of the Study:
- To determine the X-ray crystal structure of the C-terminal regulatory domain of IRF-3 (IRF-3 175C).
- To elucidate the structural basis of IRF-3 activation and its interaction with downstream partners.
Main Methods:
- X-ray crystallography was used to determine the structure of IRF-3 175C at 2.3 A resolution.
- Structural comparisons and functional analyses were performed to understand IRF-3 dimerization and binding.
Main Results:
- The crystal structure of IRF-3 175C revealed structural similarity to the Mad homology domain 2 of the Smad family.
- Phosphorylation induces IRF-3 dimerization, forming an extensive acidic pocket essential for binding to p300/CBP.
- Despite evolutionary divergence, IRF-3 shares structural homology with Smad proteins.
Conclusions:
- IRF-3's structure suggests an evolutionary origin from Smad proteins.
- Phosphorylation-mediated dimerization of IRF-3 is critical for its function in TLR signaling and innate immunity.
- IRF-3 integrates TLR and Smad signaling pathways through structural and functional mechanisms.