m6A methylation potentiates cytosolic dsDNA recognition in a sequence-specific manner

Area of Science:

• Immunology
• Molecular Biology
• Epigenetics

Background:

• Pattern recognition receptors (PRRs) are crucial for detecting microbial infections.
• Microbial DNA often contains N6-methyladenine (m6A) modifications, which are rare in mammalian DNA.

Purpose of the Study:

• To investigate the impact of m6A DNA methylation on the immunogenicity of synthetic DNA.
• To determine the mechanisms by which m6A DNA is recognized by innate immune cells.

Main Methods:

• Transfection of murine macrophages and dendritic cells with m6A-methylated and unmethylated DNA.
• Analysis of immune cell activation markers (CD69, CD86) and gene expression (Ifnβ, iNos, Cxcl10).
• Assessment of signaling pathways involving TLR, RIG-I, STING, and cGAS.

Main Results:

• m6A methylation of 5'-GATC-3' motifs augmented DNA immunogenicity in murine immune cells.
• Recognition of m6A DNA required STING and cGAS, independent of TLR and RIG-I.
• The immune response to m6A DNA was sequence-specific, with some motifs being immunostimulatory and others immunosuppressive.
• This sequence-specific response was conserved in human macrophages.

Conclusions:

• Epigenetic DNA modifications are context-dependent and differentially recognized by innate immune cells.
• m6A DNA methylation can modulate immune responses, offering potential for immune-modulating therapeutics.