Abstract 1328: Replication inhibition and mutagenicity of 8,5’-cyclopurine-2’-deoxynucleosides in Escherichia coli

Abstract

Abstract 8,5’-Cyclopurine-2’-deoxynucleosides are unique tandem DNA lesions formed by oxidation or ionizing radiation, which are repaired only by nucleotide excision repair. They have been suspected to be responsible for neurodegeneration and other diseases. But their replication properties are little studied. In the current work, we have evaluated replication of a pMS2 plasmid containing a single (5's)-8,5’-cyclo-2’-deoxyadenosine (5's-cdA) or (5's)-8,5’-cyclo-2’-deoxyguanosine (5's-cdG) at a preselected site in Escherichia coli. In the wild type E. coli cells, viability of 5's-cdA and 5's-cdG plasmids dropped to approximately 1% and 0.5%, respectively, relative to control. The viability of each was further reduced in pol II-deficient strain, but it was most pronounced in a pol V-deficient strain, where it dropped ten-fold. By contrast, viability increased 4-7-fold in a pol IV-deficient strain. Upon induction of SOS functions, viability increased ten-fold in the wild type strain. Though less pronounced, viability increased in the other strains as well. We conclude that pol V is necessary for translesion synthesis of the cyclopurines and that it may work cooperatively with pol II, which is also needed for bypass. In addition, it appears that although pol IV competes with the other bypass polymerases, it is inefficient in bypassing these lesions. In the absence of SOS, 5's-cdA-to-G mutations occurred at a low frequency, whereas 5's-cdG-to-A events were detected at a much higher frequency. With SOS, 5's-cdA-to-T and 5's-cdG-to-T were also detected. [Supported by NIEHS grant ES-013324] Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1328. doi:10.1158/1538-7445.AM2011-1328