García-Benítez, FranciscoGaillard, HélèneAguilera, Andrés2023-01-252023-01-252017-09-25http://hdl.handle.net/10668/11645During transcription, the mRNA may hybridize with DNA, forming an R loop, which can be physiological or pathological, constituting in this case a source of genomic instability. To understand the mechanism by which eukaryotic cells prevent harmful R loops, we used human activation-induced cytidine deaminase (AID) to identify genes preventing R loops. A screening of 400 Saccharomyces cerevisiae selected strains deleted in nuclear genes revealed that cells lacking the Mlp1/2 nuclear basket proteins show AID-dependent genomic instability and replication defects that were suppressed by RNase H1 overexpression. Importantly, DNA-RNA hybrids accumulated at transcribed genes in mlp1/2 mutants, indicating that Mlp1/2 prevents R loops. Consistent with the Mlp1/2 role in gene gating to nuclear pores, artificial tethering to the nuclear periphery of a transcribed locus suppressed R loops in mlp1∆ cells. The same occurred in THO-deficient hpr1∆ cells. We conclude that proximity of transcribed chromatin to the nuclear pore helps restrain pathological R loops.enMpl1/2R loopgenome instabilitynuclear porestranscriptionChromatinCytidine DeaminaseDNA ReplicationDNA, FungalGenomic InstabilityHumansNuclear PoreNuclear ProteinsSaccharomyces cerevisiaeSaccharomyces cerevisiae ProteinsTranscription, Geneticresearch article28973905open access10.1073/pnas.17078451141091-6490PMC5642707https://www.pnas.org/content/pnas/114/41/10942.full.pdfhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC5642707/pdf