Structure of the Human cGAS–DNA Complex Reveals Enhanced Control of Immune Surveillance

• Published in: Cell 2018-07, Vol.174 (2), p.300-311.e11
• Main Authors: Zhou, Wen, Whiteley, Aaron T., de Oliveira Mann, Carina C., Morehouse, Benjamin R., Nowak, Radosław P., Fischer, Eric S., Gray, Nathanael S., Mekalanos, John J., Kranzusch, Philip J.
• Format: Article
• Language: English
• Subjects: Animals; Benzofurans - chemistry; Benzofurans - metabolism; Binding Sites; Catalytic Domain; cGAS; Chemotaxis - drug effects; DNA - chemistry; DNA - metabolism; Humans; Immunologic Surveillance - physiology; innate immunity; Mice; Molecular Docking Simulation; Mutagenesis, Site-Directed; Nucleotides, Cyclic - metabolism; Nucleotides, Cyclic - pharmacology; Nucleotidyltransferases - antagonists & inhibitors; Nucleotidyltransferases - genetics; Nucleotidyltransferases - metabolism; Protein Multimerization; Protein Structure, Tertiary; Recombinant Proteins - biosynthesis; Recombinant Proteins - chemistry; Recombinant Proteins - isolation & purification; Species Specificity; STING; structural biology; Vibrio cholerae - metabolism; Vibrio cholerae - physiology
• ISSN: 0092-8674; 1097-4172; 1097-4172
• DOI: 10.1016/j.cell.2018.06.026

Cyclic GMP–AMP synthase (cGAS) recognition of cytosolic DNA is critical for immune responses to pathogen replication, cellular stress, and cancer. Existing structures of the mouse cGAS–DNA complex provide a model for enzyme activation but do not explain why human cGAS exhibits severely reduced levels of cyclic GMP–AMP (cGAMP) synthesis compared to other mammals. Here, we discover that enhanced DNA-length specificity restrains human cGAS activation. Using reconstitution of cGAMP signaling in bacteria, we mapped the determinant of human cGAS regulation to two amino acid substitutions in the DNA-binding surface. Human-specific substitutions are necessary and sufficient to direct preferential detection of long DNA. Crystal structures reveal why removal of human substitutions relaxes DNA-length specificity and explain how human-specific DNA interactions favor cGAS oligomerization. These results define how DNA-sensing in humans adapted for enhanced specificity and provide a model of the active human cGAS–DNA complex to enable structure-guided design of cGAS therapeutics. [Display omitted] •cGAS-DNA-sensing in humans is adapted for enhanced specificity•A bacterial genetic assay allows rapid mapping of human cGAS regulatory determinant•Human cGAS–DNA structures reveal altered contacts that favor DNA-length discrimination•cGAS active site variation explains species-specificity of small-molecule inhibitors The structure of the human cGAS–DNA complex reveals regulatory adaptations that balance enzymatic activity with DNA-length sensitivity, and additional features important for drug design.