cGAS bends unpaired DNA to form an unconventional structure that hyperactivates the innate immune response

Yang, S.; Wu, S.; Chen, S.; Li, X.; Chelepis, I.; Willcox, S.; Barnett, K. C.; Hu, X.; Huang, G.; Brickey, W. J.; Duncan, J. A.; Chou, W.-C.; Liu, P.; Fusco, W. G.; Torres, S. M.; Shadel, G. S.; Bowman, G.; Griffith, J. D.; Sohn, J.; Ting, J. P.- Y.

doi:10.64898/2026.05.22.726336

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bioRxiv · 10.64898/2026.05.22.726336

cGAS bends unpaired DNA to form an unconventional structure that hyperactivates the innate immune response

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Abstract

cGAS is a pattern-recognition receptor for dsDNA and forms 2cGAS:2DNA dimers followed by oligomerization into phase-separated condensates when fully-complementary DNA is studied. However, many DNAs are not fully complementary. We report that DNA with unpaired regions such as those found during transcription, recombination or replication (designated as bubble-DNA, Bu-DNA) causes cGAS hyper-activation. Hyperactivation is observed by Bu-DNA embedded in linear DNA, circular DNA, plasmid DNA and mitochondria DNA. Bu-DNA binds significantly more tightly to the cGAS catalytic domain than paired-DNA but suppresses condensation. Cryo-EM and single-molecule FRET reveal that cGAS forms 2cGAS:1DNA complexes by bending Bu-DNA into a V-shape using the unpaired region as a hinge, limiting its oligomeric state. This uncovers a novel mode of cGAS activation attributed to pattern diversity within pattern ligands.

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Yang, S., Wu, S., Chen, S., Li, X., Chelepis, I., Willcox, S., Barnett, K. C., Hu, X., Huang, G., Brickey, W. J., Duncan, J. A., Chou, W.-C., Liu, P., Fusco, W. G., Torres, S. M., Shadel, G. S., Bowman, G., Griffith, J. D., Sohn, J., Ting, J. P.- Y.. 2026-05-25. cGAS bends unpaired DNA to form an unconventional structure that hyperactivates the innate immune response. https://doi.org/10.64898/2026.05.22.726336

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