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A High Resolution Method to Monitor Phosphorylation-dependent Activation of IRF3
Published on: January 24, 2016
The pyrin domain of IFI16 forms a distinct filament structure important for IFI16-mediated enhancement of STING
Ryuichi Takahashi1, Zhikuan Zhang1, Akiko Fujimura1
1Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Abstract:
Interferon-gamma inducible protein 16 (IFI16) is a member of the HIN-200 family and has been proposed as a pathogenic DNA sensor with the dual function of activating both the inflammasome pathway and the stimulator of interferon genes (STING) pathway. Here, our cryo-EM analysis revealed that the pyrin domain (PYD) of IFI16 self-oligomerizes into a filamentous structure. The filament structure of IFI16PYD is distinct from those of PYDs in other inflammasome-related proteins, including ASC, AIM2, and NLRP3. Specifically, the IFI16PYD filament can be described as a three-start, right-handed helix assembly as for the known PYD filaments, but with a helical rise of 17.4 Å instead of ∼14 Å and a helical twist of 43.7° instead of ∼55° and lacking the C3 symmetry, resulting in a smaller diameter. Moreover, IFI16 mutants with impaired filament formation exhibited a reduced ability to enhance STING activation compared with wildtype IFI16 in a cellular reporter assay.
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