biostudies-literatureSimon AJWelch FoundationNational Institutes of HealthArnold O. BeckmanNIGMS NIH HHS11007-11019https://www.ebi.ac.uk/biostudies/studies/S-EPMC6868368biostudies-literatureUnknown47(21)Precision genome editing technologies have transformed modern biology. These technologies have arisen from the redirection of natural biological machinery, such as bacteriophage lambda proteins for recombineering and CRISPR nucleases for eliciting site-specific double-strand breaks. Less well-known is a widely distributed class of bacterial retroelements, retrons, that employ specialized reverse transcriptases to produce noncoding intracellular DNAs. Retrons' natural function and mechanism of genetic transmission have remained enigmatic. However, recent studies have harnessed their ability to produce DNA in situ for genome editing and evolution. This review describes retron biology and function in both natural and synthetic contexts. We also highlight areas that require further study to adNucleic acids researchRetrons and their applications in genome engineering.PMC6868368R01 GM124141F-1808GM124141F-1654Ellington ADFinkelstein IJSimon AJfalseRetrons and their applications in genome engineering.Precision genome editing technologies have transformed modern biology. These technologies have arisen from the redirection of natural biological machinery, such as bacteriophage lambda proteins for recombineering and CRISPR nucleases for eliciting site-specific double-strand breaks. Less well-known is a widely distributed class of bacterial retroelements, retrons, that employ specialized reverse transcriptases to produce noncoding intracellular DNAs. Retrons' natural function and mechanism of genetic transmission have remained enigmatic. However, recent studies have harnessed their ability to produce DNA in situ for genome editing and evolution. This review describes retron biology and function in both natural and synthetic contexts. We also highlight areas that require further study to ad2019-01-01T00:00:00Z2019 Dec2025-04-21T15:50:13.706Z2020-05-21T19:40:43ZS-EPMC68683683159868510.1093/nar/gkz865