title: Alkylation resistance of E. coli cells expressing different isoforms of human alkyladenine DNA glycosylase (hAAG).
abstract: The alkyladenine DNA glycosylase (AAG) has been cloned from mouse and humans. AAG knock out mouse cells are sensitized to a variety of alkylating and cross-linking agents suggesting AAG is active on a variety of substrates. In humans, two isoforms have been characterized that are generated by alternative splicing and contain either exon 1a or 1b (hAAG1 or hAAG2). In this study, we examine the ability of the both known isoforms of human AAG (hAAG) to contribute to survival of Escherichia coli from treatments with simple alkylating agents and cross-linking alkylating agents. Our results show that hAAG is effective at repairing methyl lesions when expressed in E. coli, but is unable to afford increased resistance to alkylating agents producing larger alkyl lesions such as ethyl lesions or lesions produced by the cross-linking alkylating agents N,N'-bis-chloroethyl-N-nitrosourea (BCNU), N-(2-chloroethyl)-N-nitrosourea (CNU) or mitomycin C. In the case of CNU, expression of hAAG causes increased sensitivity rather than resistance, suggesting deleterious effects of hAAG activity. We also demonstrate that there are no apparent differences between the two isoforms of hAAG when recovery from damage produced by all alkylating agents is tested.
authors.affiliation: Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, MA 01655, USA.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Bonanno
authors.forename: Jennifer
authors.initials: J
authors.lastname: Wyrzykowski
authors.forename: Wincha
authors.initials: W
authors.lastname: Chong
authors.forename: Zdenka
authors.initials: Z
authors.lastname: Matijasevic
authors.forename: Michael R
authors.initials: MR
authors.lastname: Volkert
mesh_terms: D000477:Alkylating Agents / Q000378:metabolism; D000478:Alkylation; D045647:DNA Glycosylases; D004260:DNA Repair / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008745:Methylation / Q000187:drug effects; D009699:N-Glycosyl Hydrolases / Q000235:genetics* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics* / Q000378:metabolism*; D013379:Substrate Specificity / Q000235:genetics / Q000502:physiology
chemical_list: D000477:Alkylating Agents; D007527:Isoenzymes; D011994:Recombinant Proteins; C021565:3-methyladenine-DNA glycosylase; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases