{"database":"GEO","file_versions":[{"headers":{"Content-Type":["application/json"]},"body":{"files":{"Other":["ftp://ftp.ncbi.nlm.nih.gov/geo/series/GSE330nnn/GSE330641/"]},"type":"primary"},"statusCodeValue":200,"statusCode":"OK"}],"scores":null,"additional":{"omics_type":["Other"],"species":["Escherichia coli"],"gds_type":["Other"],"full_dataset_link":["https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE330641"],"repository":["GEO"],"entry_type":["GSE"],"additional_accession":[]},"is_claimable":false,"name":"Coordinated synthesis of double-stranded DNA by a dual reverse transcriptase immune system [miniprep-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":"GSE330641","cross_references":{"GSM":["GSM9729760","GSM9729762","GSM9729751","GSM9729761","GSM9729750","GSM9729764","GSM9729753","GSM9729742","GSM9729752","GSM9729763","GSM9729744","GSM9729755","GSM9729765","GSM9729754","GSM9729743","GSM9729757","GSM9729746","GSM9729756","GSM9729745","GSM9729759","GSM9729748","GSM9729747","GSM9729758","GSM9729749"],"GPL":["35738"],"GSE":["330641"],"taxon":["Escherichia coli"]}}