Translesion synthesis DNA polymerase η exhibits a specific RNA extension activity and a transcription-associated function

We thank Andres Aguilera for providing the pCYC-LacZ plasmid for the GLRO experiments, and Szilvia Minorits for technical assistance. This work was also supported by grants from the National Research, Development and Innovation Office: GINOP-2.3.2-15-2016-00001 and GINOP-2.3.2-15-2016-00024.Peer reviewedPublisher PD

DNA-Protein Crosslinks Formation and Processing in Saccharomyces cerevisiae

Several environmental agents and intracellular metabolites promote formation of a covalent bond between protein and DNA, thus stabilising one of the most toxic DNA lesions – a DNA-protein crosslink (DPC). Bulky in their nature, DPCs prevent genuine progression of the replication and transcription machineries, thus seriously threatening DNA integrity. This work reveals two novel pathways contributing to cell survival in the presence of toxic DPC lesions: the SUMO posttranslational modification and the aspartic protease Ddi1. SUMOylation is described here to regulate the outcomes of toxic Top1-DNA trapping or formation of chemically identical covalent DPC lesions. Ddi1 is required for the efficient elimination Top1-DNA and other DPC adducts in a protease dependent manner, and is therefore proposed to act as a novel dedicated proteolytic enzyme contributing to DPC disassembly. In summary, the manuscript presents novel insights into the molecular mechanisms underlying the cellular response to toxic DPC lesions

SUMO orchestrates multiple alternative DNA-protein crosslink repair pathways

Endogenous metabolites, environmental agents, and therapeutic drugs promote formation of covalent DNA-protein crosslinks (DPCs). Persistent DPCs compromise genome integrity and are eliminated by multiple repair pathways. Aberrant Top1-DNA crosslinks, or Top1ccs, are processed by Tdp1 and Wss1 functioning in parallel pathways in Saccharomyces cerevisiae. It remains obscure how cells choose between diverse mechanisms of DPC repair. Here, we show that several SUMO biogenesis factors (Ulp1, Siz2, Slx5, and Slx8) control repair of Top1cc or an analogous DPC lesion. Genetic analysis reveals that SUMO promotes Top1cc processing in the absence of Tdp1 but has an inhibitory role if cells additionally lack Wss1. In the tdp1Δ wss1Δ mutant, the E3 SUMO ligase Siz2 stimulates sumoylation in the vicinity of the DPC, but not SUMO conjugation to Top1. This Siz2-dependent sumoylation inhibits alternative DPC repair mechanisms, including Ddi1. Our findings suggest that SUMO tunes available repair pathways to facilitate faithful DPC repair.ISSN:2666-3864ISSN:2211-124