{"database":"GEO","file_versions":[{"headers":{"Content-Type":["application/json"]},"body":{"files":{"Other":["ftp://ftp.ncbi.nlm.nih.gov/geo/series/GSE329nnn/GSE329897/"]},"type":"primary"},"statusCode":"OK","statusCodeValue":200}],"scores":null,"additional":{"omics_type":["Other"],"species":["Escherichia coli"],"gds_type":[" Expression profiling by high throughput sequencing","Other"],"full_dataset_link":["https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE329897"],"repository":["GEO"],"entry_type":["GSE"],"additional_accession":[]},"is_claimable":false,"name":"Coordinated synthesis of double-stranded DNA by a dual reverse transcriptase immune system [RIP-seq]","description":"Recent studies have revealed that defense-associated reverse transcriptase (DRT) systems mediate antiviral immunity through distinct modes of cDNA synthesis. Class I DRTs catalyze untemplated DNA synthesis with random or nucleotide-biased sequences, whereas Class II DRTs polymerize noncoding RNA-templated products, including concatemeric repeats and homopolymeric cDNA. However, how these distinct modes of cDNA synthesis are employed to drive antiviral defense remains poorly understood. Here, we report a distinctive mechanism of DRT3 immunity, in which RT enzymes from both Class I and Class II coordinate their diverse activities to produce self-complementary double-stranded DNA (dsDNA). Remarkably, whereas the DRT3a enzyme relies on a 5′-ACACAC-3′ RNA template to synthesize long poly-(dTdG) repeats, DRT3b synthesizes precise poly-(dCdA) repeats without any nucleic acid template at all. The cryo-electron microscopy structure reveals that DRT3b assembles into a hexameric complex and employs active site-adjacent residues to function as deoxyadenosine and deoxycytidine gates that enforce alternating addition to produce dinucleotide repeats, representing a unique example of amino acid-templated DNA polymerization. Strikingly, DRT3 immune systems are toxic in a genetic background lacking E. coli RecBCD, implicating host recombination machinery in limiting DRT3-mediated dsDNA levels. Consistent with this model, we discovered that the phage-encoded RecBCD inhibitor, Gam, potently triggers DRT3-mediated abortive infection. Collectively, our findings reveal how two polymerases with distinct templating strategies cooperate to generate complementary DNA and drive antiviral defense.","dates":{"publication":"2026/06/22"},"accession":"GSE329897","cross_references":{"GSM":["GSM9712880","GSM9712881","GSM9712870","GSM9712871","GSM9712882","GSM9712872","GSM9712873","GSM9712863","GSM9712874","GSM9712875","GSM9712864","GSM9712876","GSM9712865","GSM9712866","GSM9712877","GSM9712878","GSM9712867","GSM9712868","GSM9712879","GSM9712869"],"GPL":["35738"],"GSE":["329897"],"taxon":["Escherichia coli"]}}