R-loop

An R-loop is a three-stranded nucleic acid structure that forms during transcription when a nascent RNA molecule anneals back to its DNA template strand, displacing the complementary DNA strand as exposed single-stranded DNA. R-loops occur naturally and are usually resolved by dedicated repair and processing enzymes, but when their resolution is impaired, they accumulate as aberrant DNA/RNA hybrids and single-stranded DNA that can be sensed by innate immune DNA-sensing pathways such as cGAS-STING, triggering interferon-stimulated gene expression and cell-death responses.