Chromatin Architecture Explains Why Immune Cells and Epithelial Cells Produce Different Interferon Responses
Researchers found that plasmacytoid dendritic cells and epithelial cells produce different types of interferons due to pre-existing differences in chromatin accessibility at interferon gene loci, controlled by ETS and IRF transcription factors. Both cell types sense viral threats through similar pathways, but their distinct chromatin landscapes—shaped by PU.1 and IRF8 binding at composite regulatory elements—determine which interferon genes are readily accessible for activation. This discovery explains a long-standing puzzle in immunology about how genetically identical cells mount fundamentally different antiviral responses.
Using ATAC-seq analysis of primary human plasmacytoid dendritic cells (pDCs) and intestinal epithelial cells, researchers identified that cell-type-specific interferon responses are determined by constitutively established chromatin accessibility patterns established before viral infection. The type I interferon (IFN-I) locus is broadly open in pDCs but closed in epithelial cells, while the type III interferon (IFN-III) locus shows the opposite pattern. The key regulatory difference involves ETS-IRF composite elements: PU.1 and IRF8 transcription factors bind at these composite sites in pDCs, maintaining the IFN-I locus in a poised state that enables rapid activation. Epithelial cells lack these ETS factors, rendering the IFN-I locus epigenetically silent while keeping the IFN-III locus open. Additionally, intrinsic differences in promoter strength contribute to the delayed IFN-III expression observed in epithelial cells. These findings demonstrate that lineage-specific chromatin architecture and transcription factor availability, rather than differences in viral sensing pathways, determine the divergent interferon responses between these cell types.
Limitations & open questions
The study's own limitations are not detailed in the abstract provided. Additionally, the functional consequences of these chromatin differences for antiviral immunity and potential therapeutic applications remain to be explored.
What different sources said
- bioRxivCenter
Lineage-specific chromatin poising enforced by ETS-IRF composite elements determines the divergent interferon responses of plasmacytoid dendritic cells and epithelial cells
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