Structural mechanism of cytosolic DNA sensing by cGAS

Abstract

Cytosolic DNA arising from intracellular bacterial or viral infections is a powerful pathogen-associated molecular pattern (PAMP) that leads to innate immune host defence by the production of type I interferon and inflammatory cytokines. Recognition of cytosolic DNA by the recently discovered cyclic-GMP-AMP (cGAMP) synthase (cGAS) induces the production of cGAMP to activate the stimulator of interferon genes (STING). Here we report the crystal structure of cGAS alone and in complex with DNA, ATP and GTP along with functional studies. Our results explain the broad DNA sensing specificity of cGAS, show how cGAS catalyses dinucleotide formation and indicate activation by a DNA-induced structural switch. cGAS possesses a remarkable structural similarity to the antiviral cytosolic double-stranded RNA sensor 2′-5′oligoadenylate synthase (OAS1), but contains a unique zinc thumb that recognizes B-form double-stranded DNA. Our results mechanistically unify dsRNA and dsDNA innate immune sensing by OAS1 and cGAS nucleotidyl transferases.

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Figure 1: Crystal Structure of cGASMab21.
Figure 2: The cGASMab21–DNA–GTP–ATP complex.
Figure 3: Platform and Zn thumb are involved in dsDNA-dependent activity.
Figure 4: NTase and DNA-induced structural switch.
Figure 5: Model for DNA sensing by cGAS.

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Acknowledgements

We thank A. Butryn for comments on the manuscript. We thank the Max-Planck-Crystallization facility for initial crystal screening and the Swiss Light Source, European Synchrotron Radiation Facility and the German electron synchrotron Petra III for beam time and on-site assistance. This work was funded by the National Institutes of Health (U19AI083025), the European Research Council Advanced Grant 322869, and the Center for Integrated Protein Science Munich (CIPSM) to K.-P.H., by DFG grant 3717/2-1 to G.W., by GRK1721 to K.-P.H. and G.W., by DFG grant SFB670 and ERC grant 243046 to V.H.; C.C.O.M. is supported by GRK1721.

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F.C. crystallized and determined the structure of cGAS, performed biochemical assays, interpreted data and wrote the manuscript. T.D. crystallized and refined the DNA complex. C.C.O.M., A.A., T.D. and M.M. performed biochemical assays. G.W. performed biochemical assays, interpreted data and helped with structure determination. V.H. supervised the cell-based experiments and interpreted data. K.-P.H designed the research, helped with structure determination, interpreted data and wrote the manuscript.

Corresponding author

Correspondence to Karl-Peter Hopfner.

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The authors declare no competing financial interests.

Additional information

Coordinates and structure factors have been deposited at the Protein Data Bank (4JLX, 4JLZ and 4KB6).

Supplementary information

Supplementary Information

This file contains Supplementary Figures 1–6 and Supplementary Table 1. The figures show the activity both ‘in vitro’ and ‘in cells’, sequence conservation and secondary structure and the table summarizes the crystallographic data collection and model refinement statistics. (PDF 4253 kb)

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Civril, F., Deimling, T., de Oliveira Mann, C. et al. Structural mechanism of cytosolic DNA sensing by cGAS. Nature 498, 332–337 (2013). https://doi.org/10.1038/nature12305

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