Dataset Information

Abasic sites and strand breaks in DNA cause transcriptional mutagenesis in Escherichia coli.

ABSTRACT: DNA damage occurs continuously, and faithful replication and transcription are essential for maintaining cell viability. Cells in nature are not dividing and replicating DNA often; therefore it is important to consider the outcome of RNA polymerase (RNAP) encounters with DNA damage. Base damage in the DNA can affect transcriptional fidelity, leading to production of mutant mRNA and protein in a process termed transcriptional mutagenesis (TM). Abasic (AP) sites and strand breaks are frequently occurring, spontaneous damages that are also base excision repair (BER) intermediates. In vitro studies have demonstrated that these lesions can be bypassed by RNAP; however this has never been assessed in vivo. This study demonstrates that RNAP is capable of bypassing AP sites and strand breaks in Escherichia coli and results in TM through adenine incorporation in nascent mRNA. Elimination of the enzymes that process these lesions further increases TM; however, such mutants can still complete repair by other downstream pathways. These results show that AP sites and strand breaks can result in mutagenic RNAP bypass and have important implications for the biologic endpoints of DNA damage.

SUBMITTER: Clauson CL

PROVIDER: S-EPMC2840506 | biostudies-literature | 2010 Feb

REPOSITORIES: biostudies-literature

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Abasic sites and strand breaks in DNA cause transcriptional mutagenesis in Escherichia coli.

Clauson Cheryl L CL Oestreich Kenneth J KJ Austin James W JW Doetsch Paul W PW

Proceedings of the National Academy of Sciences of the United States of America 20100208 8

DNA damage occurs continuously, and faithful replication and transcription are essential for maintaining cell viability. Cells in nature are not dividing and replicating DNA often; therefore it is important to consider the outcome of RNA polymerase (RNAP) encounters with DNA damage. Base damage in the DNA can affect transcriptional fidelity, leading to production of mutant mRNA and protein in a process termed transcriptional mutagenesis (TM). Abasic (AP) sites and strand breaks are frequently oc ...[more]

PMID: 20142484

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Project description:To elucidate the contribution of pyrimidine in DNA strand breaks caused by low-energy electrons (LEEs), theoretical investigations of the LEE attachment-induced C(3')-O(3'), and C(5')-O(5') ? bond as well as N-glycosidic bond breaking of 2'-deoxycytidine-3',5'-diphosphate and 2'-deoxythymidine-3',5'-diphosphate were performed using the B3LYP/DZP++ approach. The base-centered radical anions are electronically stable enough to assure that either the C-O or glycosidic bond breaking processes might compete with the electron detachment and yield corresponding radical fragments and anions. In the gas phase, the computed glycosidic bond breaking activation energy (24.1 kcal/mol) excludes the base release pathway. The low-energy barrier for the C(3')-O(3') ? bond cleavage process (?6.0 kcal/mol for both cytidine and thymidine) suggests that this reaction pathway is the most favorable one as compared to other possible pathways. On the other hand, the relatively low activation energy barrier (?14 kcal/mol) for the C(5')-O(5') ? bond cleavage process indicates that this bond breaking pathway could be possible, especially when the incident electrons have relatively high energy (a few electronvolts). The presence of the polarizable medium greatly increases the activation energies of either C-O ? bond cleavage processes or the N-glycosidic bond breaking process. The only possible pathway that dominates the LEE-induced DNA single strands in the presence of the polarizable surroundings (such as in an aqueous solution) is the C(3')-O(3') ? bond cleavage (the relatively low activation energy barrier, ?13.4 kcal/mol, has been predicted through a polarizable continuum model investigation). The qualitative agreement between the ratio for the bond breaks of C(5')-O(5'), C(3')-O(3') and N-glycosidic bonds observed in the experiment of oligonucleotide tetramer CGAT and the theoretical sequence of the bond breaking reaction pathways have been found. This consistency between the theoretical predictions and the experimental observations provides strong supportive evidences for the base-centered radical anion mechanism of the LEE-induced single-strand bond breaking around the pyrimidine sites of the DNA single strands.

Dataset Information

Abasic sites and strand breaks in DNA cause transcriptional mutagenesis in Escherichia coli.

Publications

Abasic sites and strand breaks in DNA cause transcriptional mutagenesis in Escherichia coli.

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