TREX2 Exonuclease Causes Spontaneous Mutations and Stress-Induced Replication Fork Defects in Cells Expressing RAD51 K133A

• Published in: Cell reports (Cambridge) 2020-12, Vol.33 (12), p.108543
• Main Authors: Ko, Jun Ho, Son, Mi Young, Zhou, Qing, Molnarova, Lucia, Song, Lambert, Mlcouskova, Jarmila, Jekabsons, Atis, Montagna, Cristina, Krejci, Lumir, Hasty, Paul
• Format: Article
• Language: English
• Subjects: Animals; DNA Replication; Exodeoxyribonucleases - genetics; Exodeoxyribonucleases - metabolism; Humans; Male; Mice; Mutation; Phosphoproteins - genetics; Phosphoproteins - metabolism; Rad51 Recombinase - biosynthesis; Rad51 Recombinase - genetics; Rad51 Recombinase - metabolism; Transfection
• ISSN: 2211-1247
• DOI: 10.1016/j.celrep.2020.108543

DNA damage tolerance (DDT) and homologous recombination (HR) stabilize replication forks (RFs). RAD18/UBC13/three prime repair exonuclease 2 (TREX2)-mediated proliferating cell nuclear antigen (PCNA) ubiquitination is central to DDT, an error-prone lesion bypass pathway. RAD51 is the recombinase for HR. The RAD51 K133A mutation increased spontaneous mutations and stress-induced RF stalls and nascent strand degradation. Here, we report in RAD51 cells that this phenotype is reduced by expressing a TREX2 H188A mutation that deletes its exonuclease activity. In RAD51 cells, knocking out RAD18 or overexpressing PCNA reduces spontaneous mutations, while expressing ubiquitination-incompetent PCNA increases mutations, indicating DDT as causal. Deleting TREX2 in cells deficient for the RF maintenance proteins poly(ADP-ribose) polymerase 1 (PARP1) or FANCB increased nascent strand degradation that was rescued by TREX2 , implying that TREX2 prohibits degradation independent of catalytic activity. A possible explanation for this occurrence is that TREX2 associates with UBC13 and ubiquitinates PCNA, suggesting a dual role for TREX2 in RF maintenance.