2024-09-122024-09-122023-06Williams, J.D., Zhu, D., García Rubio, M.L., Shaltz, S., Aguilera López, A. y Jinks-Robertson, S. (2023). Spontaneous deamination of cytosine to uracil is biased to the non-transcribed DNA strand in yeast. DNA Repair, 126, 103489. https://doi.org/10.1016/j.dnarep.2023.103489.1568-78561568-7864https://hdl.handle.net/11441/162455Transcription in Saccharomyces cerevisiae is associated with elevated mutation and this partially reflects enhanced damage of the corresponding DNA. Spontaneous deamination of cytosine to uracil leads to CG>TA mutations that provide a strand-specific read-out of damage in strains that lack the ability to remove uracil from DNA. Using the CAN1 forward mutation reporter, we found that C>T and G>A mutations, which reflect deamination of the non-transcribed and transcribed DNA strands, respectively, occurred at similar rates under low-transcription conditions. By contrast, the rate of C>T mutations was 3-fold higher than G>A mutations under high-transcription conditions, demonstrating biased deamination of the non-transcribed strand (NTS). The NTS is transiently single-stranded within the ∼15 bp transcription bubble, or a more extensive region of the NTS can be exposed as part of an R-loop that can form behind RNA polymerase. Neither the deletion of genes whose products restrain R-loop formation nor the over-expression of RNase H1, which degrades R-loops, reduced the biased deamination of the NTS, and no transcription-associated R-loop formation at CAN1 was detected. These results suggest that the NTS within the transcription bubble is a target for spontaneous deamination and likely other types of DNA damage.application/pdf21 p.engAttribution-NonCommercial-NoDerivatives 4.0 Internacionalhttp://creativecommons.org/licenses/by-nc-nd/4.0/TranscriptionMutagenesisRNA polymeraseR-loopsTranscription bubbleDeaminationinfo:eu-repo/semantics/articleinfo:eu-repo/semantics/openAccess10.1016/j.dnarep.2023.103489