title: Transcriptional bypass of regioisomeric ethylated thymidine lesions by T7 RNA polymerase and human RNA polymerase II.
abstract: Alkylative damage to DNA can be induced by environmental chemicals, endogenous metabolites and some commonly prescribed chemotherapeutic agents. The regioisomeric N3-, O(2)- and O(4)-ethylthymidine (N3-, O(2)- and O(4)-EtdT, respectively) represent an important class of ethylated DNA lesions. Using nonreplicative double-stranded vectors containing an N3-EtdT, O(2)-EtdT or O(4)-EtdT at a defined site in the template strand, herein we examined the effects of these lesions on DNA transcription mediated by single-subunit T7 RNA polymerase or multisubunit human RNA polymerase II in vitro and in human cells. We found that O(4)-EtdT is highly mutagenic and exclusively induces the misincorporation of guanine opposite the lesion, whereas N3-EtdT and O(2)-EtdT display promiscuous miscoding properties during transcription. In addition, N3-EtdT and O(2)-EtdT were found to inhibit strongly DNA transcription in vitro and in certain human cells. Moreover, N3-EtdT, but not O(2)-EtdT or O(4)-EtdT, is an efficient substrate for transcription-coupled nucleotide excision repair. These findings provide new important insights into how these alkylated DNA lesions compromise the flow of genetic information, which may help to understand the risk of these lesions in living cells.
authors.affiliation: Department of Chemistry, University of California, Riverside, CA 92521-0403, USA.
authors.forename: Changjun
authors.initials: C
authors.lastname: You
authors.affiliation: Environmental Toxicology Graduate Program, University of California, Riverside, CA 92521-0403, USA.
authors.forename: Pengcheng
authors.initials: P
authors.lastname: Wang
authors.affiliation: Department of Chemistry, University of California, Riverside, CA 92521-0403, USA.
authors.forename: Xiaoxia
authors.initials: X
authors.lastname: Dai
authors.affiliation: Department of Chemistry, University of California, Riverside, CA 92521-0403, USA Environmental Toxicology Graduate Program, University of California, Riverside, CA 92521-0403, USA Yinsheng.Wang@ucr.edu.
authors.forename: Yinsheng
authors.initials: Y
authors.lastname: Wang
mesh_terms: D002460:Cell Line; D004249:DNA Damage; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D012319:RNA Polymerase II / Q000378:metabolism*; D013936:Thymidine / Q000031:analogs & derivatives* / Q000737:chemistry; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000378:metabolism*
chemical_list: D014764:Viral Proteins; C066706:N(3)-ethylthymidine; C019377:O(2)-ethylthymidine; C030119:O(4)-ethylthymidine; D012319:RNA Polymerase II; C062210:bacteriophage T7 RNA polymerase; D012321:DNA-Directed RNA Polymerases; D013936:Thymidine