biostudies-literatureKorsholm LMInnovation Fund DenmarkSteno Diabetes Center Aarhus (SDCA)Danish Research Council for Independent ResearchDanish Cancer SocietyLundbeck Foundation8019-8035https://www.ebi.ac.uk/biostudies/studies/S-EPMC6735822biostudies-literatureUnknown47(15)The nucleolus is a nuclear sub-domain containing the most highly transcribed genes in the genome. Hundreds of human ribosomal RNA (rRNA) genes, located in the nucleolus, rely on constant maintenance. DNA double-strand breaks (DSBs) in rRNA genes activate the ATM kinase, repress rRNA transcription and induce nucleolar cap formation. Yet how ribosomal-DNA (rDNA) lesions are detected and processed remains elusive. Here, we use CRISPR/Cas9-mediated induction of DSBs and report a chromatin response unique to rDNA depending on ATM-phosphorylation of the nucleolar protein TCOF1 and recruitment of the MRE11-RAD50-NBS1 (MRN) complex via the NBS1-subunit. NBS1- and MRE11-depleted cells fail to suppress rRNA transcription and to translocate rDNA into nucleolar caps. Furthermore, the DNA damage responNucleic acids researchDouble-strand breaks in ribosomal RNA genes activate a distinct signaling and chromatin response to facilitate nucleolar restructuring and repair.PMC6735822R209-A12925R219-2016-13756110-00506ADFF-1337-00128R146-A9403R192-2015-335R173-2014-1105308309DFF-1335-00763ABartek JDulina EKorsholm LMGal ZQuevedo OLuo YLin LAhmad DALarsen DHfalseDouble-strand breaks in ribosomal RNA genes activate a distinct signaling and chromatin response to facilitate nucleolar restructuring and repair.The nucleolus is a nuclear sub-domain containing the most highly transcribed genes in the genome. Hundreds of human ribosomal RNA (rRNA) genes, located in the nucleolus, rely on constant maintenance. DNA double-strand breaks (DSBs) in rRNA genes activate the ATM kinase, repress rRNA transcription and induce nucleolar cap formation. Yet how ribosomal-DNA (rDNA) lesions are detected and processed remains elusive. Here, we use CRISPR/Cas9-mediated induction of DSBs and report a chromatin response unique to rDNA depending on ATM-phosphorylation of the nucleolar protein TCOF1 and recruitment of the MRE11-RAD50-NBS1 (MRN) complex via the NBS1-subunit. NBS1- and MRE11-depleted cells fail to suppress rRNA transcription and to translocate rDNA into nucleolar caps. Furthermore, the DNA damage respon2019-01-01T00:00:00Z2019 Sep2026-05-04T21:00:50.734Z2026-04-07T20:55:59.339ZS-EPMC67358223118471410.1093/nar/gkz518