Structures of MyD88 and its oncogenic mutant reveal DNA binding with implications for cytosolic DNA sensing
- 1Harvard Medical School
Abstract
MyD88 is a universal adaptor that connects to Toll-like receptors and interleukin-1 receptors through its Toll/IL-1R homology (TIR) domain and activates inflammatory signaling via its death domain (DD). However, how MyD88TIR serves as the platform for these functions and if it has additional functions remain unclear. Here, we report cryogenic electron microscopy (cryo-EM) structures of MyD88TIR and its cancer-specific mutant L252P (previously L265P) mainly in ring and spiral forms, respectively. Both assemblies are formed by antiparallel double-filaments, using canonical TIR interfaces within each strand but unique surfaces between the strands, and position MyD88DD at the same sides of the assemblies for self-oligomerization and pathway activation. Surprisingly, these WT or L252P filaments are bound to dsDNA using the concave sides of the rings and the spirals. In vitro assays and cellular studies establish that MyD88 directly binds dsDNA and promotes inflammatory cytokine expression, particularly pro-IL-1{beta}, following dsDNA transfection or viral infection. Notably, these responses are unaffected by deficiency of UNC93B1, the essential chaperone required for trafficking endosomal nucleic acid-sensing TLRs. Structure-guide MyD88 mutant that disrupts dsDNA binding specifically compromises dsDNA-induced transcriptional program while maintaining TLR signaling. RNA-seq further reveals that MyD88 plays a crucial role in inducing gene expression upon dsDNA sensing and that about half of cGAS-dependent genes are also MyD88-dependent. Together, our structural, biochemical and genetic data support the findings that MyD88 directly engages with cytosolic dsDNA and cooperates with cGAS to promote the full innate immune transcriptional response.
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BibTeX
@misc{fontana2026structures,
title = {{Structures of MyD88 and its oncogenic mutant reveal DNA binding with implications for cytosolic DNA sensing}},
author = {P. Fontana and A. B. Tufan and P. Gunther and E. Goldberg and S. Dorfler and S. M. Vora and L. Schirokauer and J. A. Paulo and H. Suk Oh and S. P. Gygi and D. M. Knipe and H. Wu},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.21.760499},
url = {https://www.biorxiv.org/content/10.64898/2026.10.21.760499v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Structures of MyD88 and its oncogenic mutant reveal DNA binding with implications for cytosolic DNA sensing
AU - P. Fontana
AU - A. B. Tufan
AU - P. Gunther
AU - E. Goldberg
AU - S. Dorfler
AU - S. M. Vora
AU - L. Schirokauer
AU - J. A. Paulo
AU - H. Suk Oh
AU - S. P. Gygi
AU - D. M. Knipe
AU - H. Wu
PY - 2026
DA - 2026/10/21
PB - bioRxiv
DO - 10.64898/2026.10.21.760499
UR - https://www.biorxiv.org/content/10.64898/2026.10.21.760499v1
AB - MyD88 is a universal adaptor that connects to Toll-like receptors and interleukin-1 receptors through its Toll/IL-1R homology (TIR) domain and activates inflammatory signaling via its death domain (DD). However, how MyD88TIR serves as the platform for these functions and if it has additional functions remain unclear. Here, we report cryogenic electron microscopy (cryo-EM) structures of MyD88TIR and its cancer-specific mutant L252P (previously L265P) mainly in ring and spiral forms, respectively. Both assemblies are formed by antiparallel double-filaments, using canonical TIR interfaces within each strand but unique surfaces between the strands, and position MyD88DD at the same sides of the assemblies for self-oligomerization and pathway activation. Surprisingly, these WT or L252P filaments are bound to dsDNA using the concave sides of the rings and the spirals. In vitro assays and cellular studies establish that MyD88 directly binds dsDNA and promotes inflammatory cytokine expression, particularly pro-IL-1{beta}, following dsDNA transfection or viral infection. Notably, these responses are unaffected by deficiency of UNC93B1, the essential chaperone required for trafficking endosomal nucleic acid-sensing TLRs. Structure-guide MyD88 mutant that disrupts dsDNA binding specifically compromises dsDNA-induced transcriptional program while maintaining TLR signaling. RNA-seq further reveals that MyD88 plays a crucial role in inducing gene expression upon dsDNA sensing and that about half of cGAS-dependent genes are also MyD88-dependent. Together, our structural, biochemical and genetic data support the findings that MyD88 directly engages with cytosolic dsDNA and cooperates with cGAS to promote the full innate immune transcriptional response.
ER -