TORC2 inhibition triggers yeast chromosome fragmentation through misregulated Base Excision Repair of clustered oxidation events

• Published in: Nature communications 2024-11, Vol.15 (1), p.9908-20, Article 9908
• Main Authors: Shimada, Kenji, Tarashev, Cleo V. D., Bregenhorn, Stephanie, Gerhold, Christian B., van Loon, Barbara, Roth, Gregory, Hurst, Verena, Jiricny, Josef, Helliwell, Stephen B., Gasser, Susan M.
• Format: Article
• Language: English
• Subjects: 38/44; 45; 45/29; 45/71; 49; 631/337; 631/45; 631/67; 631/80; 82/29; 82/58; Accumulation; Actin; Actins - metabolism; Base excision repair; Cell death; Chromatin; Chromosomes; Chromosomes, Fungal - genetics; Chromosomes, Fungal - metabolism; Deoxyribonucleic acid; DNA; DNA Breaks, Double-Stranded - drug effects; DNA damage; DNA polymerase; DNA Repair; DNA-directed DNA polymerase; Excision Repair; Filaments; Fragmentation; Humanities and Social Sciences; Kinases; Lesions; multidisciplinary; Nuclear transport; Oxidation; Oxidation-Reduction; Rad1 protein; Replication Protein A; Saccharomyces cerevisiae - drug effects; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; Science; Science (multidisciplinary); Yeast; Yeasts
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-54142-z

Combinational therapies provoking cell death are of major interest in oncology. Combining TORC2 kinase inhibition with the radiomimetic drug Zeocin results in a rapid accumulation of double-strand breaks (DSB) in the budding yeast genome. This lethal Yeast Chromosome Shattering (YCS) requires conserved enzymes of base excision repair. YCS can be attenuated by eliminating three N -glycosylases or endonucleases Apn1/Apn2 and Rad1, which act to convert oxidized bases into abasic sites and single-strand nicks. Adjacent lesions must be repaired in a step-wise fashion to avoid generating DSBs. Artificially increasing nuclear actin by destabilizing cytoplasmic actin filaments or by expressing a nuclear export-deficient actin interferes with this step-wise repair and generates DSBs, while mutants that impair DNA polymerase processivity reduce them. Repair factors that bind actin include Apn1, RFA and the actin-dependent chromatin remodeler INO80C. During YCS, increased INO80C activity could enhance both DNA polymerase processivity and repair factor access to convert clustered lesions into DSBs. Shimada et al. show that uncoordinated repair by base excision repair generates a lethal accumulation of DNA double-strand breaks at clustered lesions. Rapid conversion of oxidative DNA damage into fragmented chromosomes stems from TORC2 inhibition.