{"doi":"10.1016/j.jbc.2022.102802","title":"The MRN complex and topoisomerase IIIa–RMI1/2 synchronize DNA resection motor proteins","abstract":"DNA resection—the nucleolytic processing of broken DNA ends—is the first step of homologous recombination. Resection is catalyzed by the resectosome, a multienzyme complex that includes bloom syndrome helicase (BLM), DNA2 or exonuclease 1 nucleases, and additional DNA-binding proteins. Although the molecular players have been known for over a decade, how the individual proteins work together to regulate DNA resection remains unknown. Using single-molecule imaging, we characterized the roles of the MRE11–RAD50–NBS1 complex (MRN) and topoisomerase IIIa (TOP3A)–RMI1/2 during long-range DNA resection. BLM partners with TOP3A–RMI1/2 to form the BTRR (BLM–TOP3A–RMI1/2) complex (or BLM dissolvasome). We determined that TOP3A–RMI1/2 aids BLM in initiating DNA unwinding, and along with MRN, stimulates DNA2-mediated resection. Furthermore, we found that MRN promotes the association between BTRR and DNA and synchronizes BLM and DNA2 translocation to prevent BLM from pausing during resection. Together, this work provides direct observation of how MRN and DNA2 harness the BTRR complex to resect DNA efficiently and how TOP3A–RMI1/2 regulates the helicase activity of BLM to promote efficient DNA repair. DNA resection—the nucleolytic processing of broken DNA ends—is the first step of homologous recombination. Resection is catalyzed by the resectosome, a multienzyme complex that includes bloom syndrome helicase (BLM), DNA2 or exonuclease 1 nucleases, and additional DNA-binding proteins. Although the molecular players have been known for over a decade, how the individual proteins work together to regulate DNA resection remains unknown. Using single-molecule imaging, we characterized the roles of the MRE11–RAD50–NBS1 complex (MRN) and topoisomerase IIIa (TOP3A)–RMI1/2 during long-range DNA resection. BLM partners with TOP3A–RMI1/2 to form the BTRR (BLM–TOP3A–RMI1/2) complex (or BLM dissolvasome). We determined that TOP3A–RMI1/2 aids BLM in initiating DNA unwinding, and along with MRN, stimulates DNA2-mediated resection. Furthermore, we found that MRN promotes the association between BTRR and DNA and synchronizes BLM and DNA2 translocation to prevent BLM from pausing during resection. Together, this work provides direct observation of how MRN and DNA2 harness the BTRR complex to resect DNA efficiently and how TOP3A–RMI1/2 regulates the helicase activity of BLM to promote efficient DNA repair. Homologous recombination (HR) is one of two major eukaryotic dsDNA break (DSB) repair pathways. HR uses the intact sister chromatid during the S/G2 phase to promote error-free repair of DSBs (1Jasin M. Rothstein R. Repair of strand breaks by homologous recombination.Cold Spring Harb. Perspect. Biol. 2013; 5: a012740Crossref PubMed Scopus (594) Google Scholar, 2Mathiasen D.P. Lisby M. Cell cycle regulation of homologous recombination in Saccharomyces cerevisiae.FEMS Microbiol. Rev. 2014; 38: 172-184Crossref PubMed Scopus (48) Google Scholar). HR initiates when the resection machinery, termed the resectosome, assembles to process (resect) the genome to generate kilobase-length stretches of ssDNA (3Cejka P. DNA end resection: nucleases team up with the right partners to initiate homologous recombination.J. Biol. Chem. 2015; 290: 22931-22938Abstract Full Text Full Text PDF PubMed Scopus (141) Google Scholar, 4Heyer W.-D. Ehmsen K.T. Liu J. Regulation of homologous recombination in eukaryotes.Annu. Rev. Genet. 2010; 44: 113-139Crossref PubMed Scopus (762) Google Scholar, 5Huertas P. DNA resection in eukaryotes: deciding how to fix the break.Nat. Struct. Mol. Biol. 2010; 17: 11-16Crossref PubMed Scopus (307) Google Scholar, 6Mimitou E.P. Symington L.S. Sae2, Exo1 and Sgs1 collaborate in DNA double-strand break processing.Nature. 2008; 455: 770-774Crossref PubMed Scopus (783) Google Scholar, 7Myler L.R. Finkelstein I.J. Eukaryotic resectosomes: a single-molecule perspective.Prog. Biophys. Mol. Biol. 2017; 127: 119-129Crossref PubMed Scopus (7) Google Scholar, 8Rona","journal":"Journal of Biological Chemistry","year":2022,"id":261635,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":15,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9476,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2022-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":916500,"name":"Giaochau Nguyen","orcid":"0000-0002-0711-804X","position":1,"is_corresponding":false},{"id":262645,"name":"Hung‐Che Kuo","orcid":"0000-0002-8577-1706","position":2,"is_corresponding":false},{"id":105935,"name":"Ilya J. Finkelstein","orcid":"0000-0002-9371-2431","position":3,"is_corresponding":false},{"id":258484,"name":"Michael M. Soniat","orcid":"0000-0003-3670-4344","position":0,"is_corresponding":true}],"reference_count":87,"raw_metadata":null,"created_at":"2026-07-19T00:26:16.663144Z","pmid":"36529288","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}