Table 3. DNA ligand structures that indicate non-self.

PowerPoint slide

Structure	Recognized structure	Receptor or effector molecule	Origin
	Base-paired DNA ≥40-80 bp (≥25 bp in mouse cells)	cGAS, AIM2 (human); cGAS (mouse)	Eukaryotic genomic DNA, bacterial plasmid DNA, dsDNA viruses and lentivirus dsDNA
	G-rich Y-form DNA: base paired DNA ≥12 bp plus unpaired G in adjacent ssDNA (G indicated in red)	cGAS	Long ssDNA with secondary structures: reverse transcripts (cDNA) of lentiviruses, endogenous retroviruses and retroelements
...CG..	CpG-rich DNA. CpG methylation blocks TLR9 recognition	TLR9	Unmethylated DNA from bacteria; DNA from viruses and host
...ATATATATATATATATATATATATATATATA..	AT-rich 'ssDNA'*	RNA polymerase III and RIG-I	Unclear
	Long DNA–RNA hybrids	cGAS	Reverse transcript of cDNA–RNA template hybrids of lentiviruses, endogenous retroviruses and retroelements
	Short DNA–RNA hybrid	TLR9	Hybrids of RNA transcripts plus DNA template (RNase H deficiency)

AIM2, absent in melanoma 2; cGAS, cyclic GMP–AMP synthetase; dsDNA, double-stranded DNA; ssDNA, single-stranded DNA; RIG-I, retinoic acid inducible gene I; RNase H, ribonuclease H; TLR9, Toll-like receptor 9.

*A self-complementary ssDNA that in principle is only unpaired at high temperature.