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Molecular Mechanisms of Mutagenesis Induced by DNA Repair
Author(s) -
Shen Birong,
Chapman Joseph,
Furano Anthony V.
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.906.15
Subject(s) - apobec , shuttle vector , mutagenesis , dna repair , base excision repair , mutation , cytidine deaminase , biology , genetics , dna , dna mismatch repair , microbiology and biotechnology , vector (molecular biology) , gene , genome , recombinant dna
Cancer is a complicated outcome of multiple somatic mutations, however, the molecular mechanisms underlying most of the mutations are unknown. Previous work in our lab using a shuttle vector system showed that repair of mismatched base pairs and other lesions induced mutations in flanking DNA. Most of these mutations exhibited a mutational spectrum typical of a cytidine deaminase, APOBEC3B (A3B). We also showed that both base excision repair and mismatch repair (BER & MMR) are required and the amount of APOBEC bound to the shuttle vector is proportionate to the extent of mutagenesis. We therefore postulated that the single‐stranded DNA substrate of the APOBEC deaminase can be generated during repair (Chen et al eLife 2014;3:e02001). Recent studies reported the involvement of A3B in generating mutations in some cancers, an example of the so‐called “mutator phenotype” long‐known to typify many cancers. We are currently using our shuttle vector to elucidate the mechanism of APOBEC‐mediated mutations in breast cancer cell lines. We found that repair of pre‐formed mismatches inserted into the shuttle vector can induce APOBEC‐mediated mutations, indicating that this system can monitor and reflect the mutational environment in tumor cells. We showed that two cancer cell lines, which contained comparable amounts of A3B, exhibited dramatically different repair‐induced mutation rates. Therefore, we postulated that the mutation rate is related to the amount of the repair‐generated APOBEC single‐stranded DNA substrate in each cell line, perhaps due to dysregulation of their DNA repair enzymes. Quantification of these enzymes showed that the relative level of some BER genes was positively correlated with repair‐induced mutagenesis, and preliminary results showed that knock down of one such gene reduced mutagenesis. Thus, our shuttle vector system could provide a tractable experimental system to explore the mechanism of the cancer cell mutator phenotype.