Mutagenesis in TLS polymerase KO TK6 cells with cisplatin and 4-NQO
DNA damage occasionally leads to mutations even in DNA repair proficient cells via translesion synthesis (TLS), an efficient but error prone DNA damage tolerance pathway. In the human genome there are three closely related Y-family TLS polymerases (eta, kappa, iota). Polymerase eta is specialised for the error-free replication of UV adducts, while polymerase kappa is known to replicate over various heterocyclic DNA adducts. The function of polymerase iota is less clear and this gene is missing from several vertebrate clades. yeast, most birds, and plants. Using wild type and TLS polymerase (POLH, POLK, POLI) knockout human TK6 cell lines and whole genome sequencing we reveal the contribution of these polymerases to mutagenesis induced by the common chemotherapy agent cisplatin and the smoke-mimicking compound 4-nitroquinoline-1-oxide (4-NQO). We found that polymerase iota specifically introduces C>T mutations at both cisplatin and 4-NQO lesions. Using non-negative matrix factorisation, we derived a polymerase iota specific base substitution signature, which corresponds to COSMIC cancer mutational signature SBS31. By analysing the mutational spectra in more than 3500 human metastatic tumours we showed that SBS31 in platinum therapy treated samples and SBS92 in smoking-related cancers is associated with polymerase iota expression. Our study defines an in vivo mutagenic function for polymerase iota and highlights its role in tissue-dependent chemotherapy-induced mutagenesis that may contribute to tumour heterogeneity.
DNA damage occasionally leads to mutations even in DNA repair proficient cells via translesion synthesis (TLS), an efficient but error prone DNA damage tolerance pathway. In the human genome there are three closely related Y-family TLS polymerases (eta, kappa, iota). Polymerase eta is specialised for the error-free replication of UV adducts, while polymerase kappa is known to replicate over various heterocyclic DNA adducts. The function of polymerase iota is less clear and this gene is missing from several vertebrate clades. yeast, most birds, and plants. Using wild type and TLS polymerase (POLH, POLK, POLI) knockout human TK6 cell lines and whole genome sequencing we reveal the contribution of these polymerases to mutagenesis induced by the common chemotherapy agent cisplatin and the smoke-mimicking compound 4-nitroquinoline-1-oxide (4-NQO). We found that polymerase iota specifically introduces C>T mutations at both cisplatin and 4-NQO lesions. Using non-negative matrix factorisation, we derived a polymerase iota specific base substitution signature, which corresponds to COSMIC cancer mutational signature SBS31. By analysing the mutational spectra in more than 3500 human metastatic tumours we showed that SBS31 in platinum therapy treated samples and SBS92 in smoking-related cancers is associated with polymerase iota expression. Our study defines an in vivo mutagenic function for polymerase iota and highlights its role in tissue-dependent chemotherapy-induced mutagenesis that may contribute to tumour heterogeneity.
Research Centre for Natural Sciences