Sequence-specific activation of the DNA sensor cGAS by Y-form DNA structures as found in primary HIV-1 cDNA

Nat Immunol. 2015 Oct;16(10):1025-33. doi: 10.1038/ni.3267. Epub 2015 Sep 7.


Cytosolic DNA that emerges during infection with a retrovirus or DNA virus triggers antiviral type I interferon responses. So far, only double-stranded DNA (dsDNA) over 40 base pairs (bp) in length has been considered immunostimulatory. Here we found that unpaired DNA nucleotides flanking short base-paired DNA stretches, as in stem-loop structures of single-stranded DNA (ssDNA) derived from human immunodeficiency virus type 1 (HIV-1), activated the type I interferon-inducing DNA sensor cGAS in a sequence-dependent manner. DNA structures containing unpaired guanosines flanking short (12- to 20-bp) dsDNA (Y-form DNA) were highly stimulatory and specifically enhanced the enzymatic activity of cGAS. Furthermore, we found that primary HIV-1 reverse transcripts represented the predominant viral cytosolic DNA species during early infection of macrophages and that these ssDNAs were highly immunostimulatory. Collectively, our study identifies unpaired guanosines in Y-form DNA as a highly active, minimal cGAS recognition motif that enables detection of HIV-1 ssDNA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Cells, Cultured
  • DNA, Complementary / chemistry*
  • DNA, Complementary / genetics
  • DNA, Complementary / immunology
  • DNA, Viral / chemistry*
  • DNA, Viral / genetics
  • DNA, Viral / immunology*
  • HEK293 Cells
  • HIV-1 / genetics*
  • HIV-1 / immunology*
  • Humans
  • Immunization
  • Interferon-alpha / immunology*
  • Mice
  • Nucleotidyltransferases / genetics*


  • DNA, Complementary
  • DNA, Viral
  • Interferon-alpha
  • Nucleotidyltransferases
  • cGAS protein, mouse