(5′ S)-8,5′-Cyclo-2′-Deoxyguanosine Is a Strong Block to Replication, a Potent pol V-Dependent Mutagenic Lesion, and Is Inefficiently Repaired in Escherichia coli
Document Type
Article
Publication Date
5-17-2011
Description
8,5′-Cyclopurines, making up an important class of ionizing radiation-induced tandem DNA damage, are repaired only by nucleotide excision repair (NER). They accumulate in NER-impaired cells, as in Cockayne syndrome group B and certain Xeroderma Pigmentosum patients. A plasmid containing (5′S)-8,5′-cyclo-2′-deoxyguanosine (S-cdG) was replicated in Escherichia coli with specific DNA polymerase knockouts. Viability was <1% in the wild-type strain, which increased to 5.5% with SOS. Viability decreased further in a pol II- strain, whereas it increased considerably in a pol IV- strain. Remarkably, no progeny was recovered from a pol V- strain, indicating that pol V is absolutely required for bypassing S-cdG. Progeny analyses indicated that S-cdG is significantly mutagenic, inducing ∼34% mutation with SOS. Most mutations were S-cdG → A mutations, though S-cdG → T mutation and deletion of 5′C also occurred. Incisions of purified UvrABC nuclease on S-cdG, S-cdA, and C8-dG-AP on a duplex 51-mer showed that the incision rates are C8-dG-AP > S-cdA > S-cdG. In summary, S-cdG is a major block to DNA replication, highly mutagenic, and repaired slowly in E. coli.
Citation Information
Jasti, Vijay P.; Das, Rajat S.; Hilton, Benjamin A.; Weerasooriya, Savithri; Zou, Yue; and Basu, Ashis K.. 2011. (5′ S)-8,5′-Cyclo-2′-Deoxyguanosine Is a Strong Block to Replication, a Potent pol V-Dependent Mutagenic Lesion, and Is Inefficiently Repaired in Escherichia coli. Biochemistry. Vol.50(19). 3862-3865. https://doi.org/10.1021/bi2004944 PMID: 21491964 ISSN: 0006-2960