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Activation of the Interferon Regulatory Factors: Crystal Structure of Dimeric IRF-5 Bill Royer, Weijun Chen, Suvana Lam, Hema Srinath, Celia Schiffer, Kate Fitzgerald and Kai Lin University of Massachusetts Worcester (not Amherst)
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Immediate and Delayed Anti-Viral Responses IFN- IFN- IFNAR Jak1 Tyk2 Stat2 Stat1 IRF-9 (ISGF3) other cytokines, anti-viral genes IFN- / virus IRF3 IFN- genes P P IFN- gene IRF3 P P
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TLR7, TLR8 ssRNA MyD88 TBK1 IKK IRF7 IRAK4 IRAK1 TRAF6 Ub TABs 1 TAK1 2 3 IKK IKK IKK P MAPKs NF- B I Bs P Ub P I Bs 26S proteasome NF- B IRF7 ATF2/c-Jun IFN IRF5 NF- B Inflammatory cytokines Cytoplasm Endosome Nucleus IFN s IRF7 TLR9 dsDNA virus MyD88 TRAF6 Ub IRF5 Ub IRF5 ? P Innate immunity is triggered by the recognition of “pathogen-associated molecular patterns” such as viral nucleic acids by Toll-like receptors (TLR) or cytoplasmic receptors.
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IRFs are activated by phosphorylation in the C-terminal domain P PP Cytoplasm Nucleus C N CBP PP DD PP
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Serine PO 4 sites B.Y. Qin, et al. K. Lin (2003) Nat. Struct. Biol. 10, 913 -921 K. Takahashi, et al. F. Inagaki (2003) Nat. Struct. Biol. 10, 922-927 Domain structure of human IRF-3 110 427 NES DBD 1 NLS 200 IAD 173 427 AUD RVGGASSLENTVDLHISNSHPLSLTS 380 IRF-3 transactivation domain construct IRF-3 acts as a molecular sentry for viral infection in all cell types.
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N C IRF-3 (residues 173-427 ) Structure of IRF-3 transactivation domain in complex with CBP supports the hypothesis that the autoinhibitory region masks CBP binding site B.Y. Qin, et al. K. Lin (2005) Structure 13, 1269-1277 IRF-3 (residues 173-394 ) CBP (2067-2112 ) N
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IRF-5 The autoinhibition of IRF-5 is less tight than that for the ubiquitously expressed IRF-3. IRF-5 is activated by: viral expression type I interferon tumor suppressor p53 IRF-5 activates type I interferon inflammatory cytokines tumor suppressors Human mutations of IRF-5 have been implicated in systemic lupus erythematosis multiple sclerosis Sjogrens syndrome Inflamatory bowel disease IRF-5 k.o. mice show susceptibility to viral infection susceptibility to tumors
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110 427 NES DBD 1 NLS 200 405 IAD 173 427 AUD Domain structure of Human IRF-3 and IRF-5 RVGGASSLENTVDLHISNSHPLSLTS SGELSWSADSIRLQISNPDIKDRMV NES DBD NLS IAD 380 IRF-3 IRF-3 transactivation domain construct IRF-5 (variant 4) IRF-5 transactivation domain construct IAD 222467 NLS 421 455 421467 233140 1
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Interactions of CBP (2067-2112) with IRF-5 (222-467) and phosphomimetic mutants based on ITC data Complex K d Change in affinity CBP – IRF-51.64 M1.0 fold CBP – IRF-5 (S427D)0.96 M1.7 fold CBP – IRF-5 (S425D)0.71 M2.3 fold CBP – IRF-5 (S436D)0.67 M2.4 fold CBP – IRF-5 (S430D)0.56 M2.9 fold
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0 200 400 600 mAU(280 nm) 12.013.014.015.016.017.018.019.0 Volume (ml) IRF-5 IRF-5 + CBP CBP 200 400 600 800 mAU (280 nm) 13.014.015.016.017.0 Volume (ml) 0 250 µM IRF-5 WT 100 µM 50 µM 450 µM 0 200 400 600 800 mAU (280 nm) 13.014.015.016.017.0 Volume (ml) IRF-5 S430D 450 µM 250 µM 100 µM 50 µM mAU (280 nm) 0 200 400 600 12.0 13.014.015.016.017.018.019.0 Volume (ml) IRF-5 S430D IRF-5 S430D + CBP CBP Size exclusion chromatography to investigate oligomerization of IRF-5 (222-467) and IRF-5 S430D Monomer Dimer
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IRF-3 complex with CBP C N IRF-5 dimeric subunit C N Helix 2 Helix 5 Helix 4 Helix 3 Helix 1 IRF-3 autoinhibited monomer C N Helix 5
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IRF-5 dimeric subunit IRF-3 autoinhibited monomer IRF-3 complex with CBP
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IRF-5 (222-467) S430D Dimer Helix 5 N N C C
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IRF-5 (222-467) S430D Dimer Helix 5 N N C C
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Helix 5 plays key alternate roles in IRF autoinhibition and dimerization. IRF-5 dimer IRF-3 monomer
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R353 I431’ L433’ I435’ S430’(D) S427’ S425 S436’ K449’ V445’ D442’ R328 L403 Y303 L307 V310 D312 F279 Helix 5 Helix 2 Helix 4 Key interface residues in the IRF-5 dimer R328 D442’ R353 S436’ Helix 5
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R353 I431’ L433’ I435’ S430’(D) S427’ S425 S436’ K449’ V445’ D442’ R328 L403 Y303 L307 V310 D312 F279 Helix 5 Helix 2 Helix 4 V391 L393 S396 I395 Helix 1 Helix 4 IRF-5 DimerIRF-3 Monomer
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R353 I431’ L433’ I435’ S430’(D) S427’ S425 S436’ K449’ V445’ D442’ R328 L403 Y303 L307 V310 D312 F279 Helix 5 Helix 2 Helix 4 Key interface residues in the IRF-5 dimer R328 D442’ R353 S436’ Helix 5
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IRF5-S430D & CBP IRF5-S430D/R353D & CBP IRF5-S430D/D442R & CBP IRF5-S430D/V310D & CBP IRF5-S430D/R328E & CBP IRF5-S436D/R328E & CBP 0 100 200 300 400 500 600 mAU (280 nm) 1314151617181920 Volume (ml) Dimer Monomer CBP Mutation of interface residues disrupt dimer formation of IRF-5 in solution
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Disruption of dimerization by mutation of interface residues inhibits IRF-5 activation HEK293 Cells IFN lucerferase (Fold Induction)
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I431’ L433’ I435’ S430’(D) S427’ S425 S436’ K449’ V445’ D442’ R353 R328 L403 Y303 L307 V310 D312 F279 Helix 5 Helix 2 (homologous IRF3 residue number for absolutely conserved residues) (L362) (R285) Helix 5 R328 D442’ R353 S436’ Helix 5
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IRF3-S386D/S396D/L362D & CBP IRF3-S386D/S396D/R285E & CBP IRF3-S386D/396D & CBP 0 100 200 300 400 mAU (280 nm) Volume (ml) 12.013.014.015.016.017.018.019.020.0 Dimer Monomer CBP Mutation of IRF-3 residues homologous to IRF-5 dimeric interface residues disrupts formation of the IRF-3 dimer in solution
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Disruption of IRF-3 dimerization inhibits its activation IFN lucerferase (Fold Induction ) HEK293 Cells Published IRF-3 mutants reinterpreted in light of our structure also support the crystallographically observed IRF- 5 dimer as representing the active state of IRF-3
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Relationship of the IRF-5 transactivation domain dimer with IRF-3 DNA binding Domains D. Panne, T. Maniatis & S.C. Harrison (2007) Cell 129, 1111-1123
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(Morphing CNS script from the Yale Morph Server, http://molmovdb.org) Phosphorylation IRF activation, dimerization and CBP binding C-term
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(Morphing CNS script from the Yale Morph Server, http://molmovdb.org) Phosphorylation IRF activation, dimerization and CBP binding
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P P P P P Helix 5 DBD CBP binding site DBD CBP binding site DBD Helix 5 Nucleus Cytoplasm DBD P P P P Helix 5 CBP binding site DBD CBP binding site Helix 5 P P P P DBD CBP binding site DBD CBP binding site CBP
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University of Massachusetts, Worcester Dept. of Biochemistry and Molecular Pharmacology Kai Lin Weijun Chen Suvana Lam Hema Srinath Brendan Hilbert Celia Schiffer Department of Medicine Kate Fitzgerald Zhaozhao Jiang $ - NIH
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Sequence alignment of the C-terminal transactivation domains of human IRF family members
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The IFN Enhanceosome IRF3 IRF7
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D. Panne, T. Maniatis & S.C. Harrison (2007) Cell 129, 1111-1123 Binding of four N-terminal DNA Binding Domains of IRF-3 to promoter as part of IFN- enhanceosome
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