10 Facts about R-Loops

10 facts about R-loops (please add facts in the comments)

1. Cellular structures that are a DNA-RNA Hybrid
2. R-loops are 3 stranded Structures: Made when an RNA hybridizes to a complementary DNA and a single-stranded DNA
3. First described in 1976
3.1 First evidence for R-loop formation in Bacteria 1994, then rapidly in other organisms as well
4. First observed by electron microscopy under conditions of 70% formamide, more thermodynamically stable then double-stranded DNA under these conditions
5. Essential positive function in human mitochondrial DNA replication
6. Can be probed with antibodies
7. Two views:
  7.1 Co-Transcriptional -- RNA forms in cis during transcription behind the RNA polymerase
  7.2 Movable -- can hybridize to homologous DNA at another location besides the location of transcription.
8. R-loops are associated with epigenetic mechanisms governing transcription.
9. Many proteins regulate R-loop concentration either directly or indirectly, most prevent RNA from hybridizing to DNA
10. Repetitive non-template DNA strand can form structures which stabilize R-loops.

The article below discusses R-loop mechanisms implicated in human disease, and R-loops as drug targets:

Out of Balance: R-loops in Human Disease

Groh M, Gromak N (2014) Out of Balance: R-loops in Human Disease. PLoS Genet 10(9): e1004630. doi: 10.1371/journal.pgen.1004630