MRC1 and cancer: Applying a similar approach to a range of DNA repair deficient and proficient cancers with suspected genotoxic exposures, we were able to characterise several cases of DNA damage-repair interactions leading to increased mutagenesis and/or altered signatures, such as POLEEXO and MMR, tissue-specific changes of the MMR deficiency signature, UV damage and NER, or APOBEC-induced mutagenesis and TLS (Fig. 2d, Supplementary Fig. 3, Supplementary Note 4).