title: Structural and functional analyses of DNA-sensing and immune activation by human cGAS.
abstract: The detection of cytosolic DNA, derived from pathogens or host cells, by cytosolic receptors is essential for appropriate host immune responses. Cyclic GMP-AMP synthase (cGAS) is a newly identified cytosolic DNA receptor that produces cyclic GMP-AMP, which activates stimulator of interferon genes (STING), resulting in TBK1-IRF3 pathway activation followed by the production of type I interferons. Here we report the crystal structure of human cGAS. The structure revealed that a cluster of lysine and arginine residues forms the positively charged DNA binding surface of human cGAS, which is important for the STING-dependent immune activation. A structural comparison with other previously determined cGASs and our functional analyses suggested that a conserved zinc finger motif and a leucine residue on the DNA binding surface are crucial for the DNA-specific immune response of human cGAS, consistent with previous work. These structural features properly orient the DNA binding to cGAS, which is critical for DNA-induced cGAS activation and STING-dependent immune activation. Furthermore, we showed that the cGAS-induced activation of STING also involves the activation of the NF-κB and IRF3 pathways. Our results indicated that cGAS is a DNA sensor that efficiently activates the host immune system by inducing two distinct pathways.
authors.affiliation: Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan ; Global Research Cluster, RIKEN, Wako, Saitama, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Kato
authors.forename: Ryohei
authors.initials: R
authors.lastname: Ishii
authors.forename: Eiji
authors.initials: E
authors.lastname: Goto
authors.forename: Ryuichiro
authors.initials: R
authors.lastname: Ishitani
authors.forename: Fuminori
authors.initials: F
authors.lastname: Tokunaga
authors.forename: Osamu
authors.initials: O
authors.lastname: Nureki
mesh_terms: D018360:Crystallography, X-Ray; D003600:Cytosol / Q000276:immunology / Q000378:metabolism; D004247:DNA / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D004789:Enzyme Activation / Q000276:immunology; D057809:HEK293 Cells; D006801:Humans; D007109:Immunity / Q000276:immunology*; D015151:Immunoblotting; D050838:Interferon Regulatory Factor-3 / Q000276:immunology / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D016328:NF-kappa B / Q000276:immunology / Q000378:metabolism; D009690:Nucleic Acid Conformation; D009713:Nucleotidyltransferases / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D010766:Phosphorylation / Q000276:immunology; D011485:Protein Binding / Q000276:immunology; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D015398:Signal Transduction / Q000276:immunology; D000099197:STING Protein; D000099235:Cyclic Guanosine Monophosphate-Adenosine Monophosphate Synthase
chemical_list: D004247:DNA; D050838:Interferon Regulatory Factor-3; D008565:Membrane Proteins; D016328:NF-kappa B; D009713:Nucleotidyltransferases; C494232:IRF3 protein, human; C532857:STING1 protein, human; D000099197:STING Protein; C578390:cGAS protein, human; D000099235:Cyclic Guanosine Monophosphate-Adenosine Monophosphate Synthase