RESUMO
Environmental factors such as tobacco smoking may have long-lasting effects on DNA methylation patterns, which might lead to changes in gene expression and in a broader context to the development or progression of various diseases. We conducted an epigenome-wide association study (EWAs) comparing current, former and never smokers from 1793 participants of the population-based KORA F4 panel, with replication in 479 participants from the KORA F3 panel, carried out by the 450K BeadChip with genomic DNA obtained from whole blood. We observed wide-spread differences in the degree of site-specific methylation (with p-values ranging from 9.31E-08 to 2.54E-182) as a function of tobacco smoking in each of the 22 autosomes, with the percent of variance explained by smoking ranging from 1.31 to 41.02. Depending on cessation time and pack-years, methylation levels in former smokers were found to be close to the ones seen in never smokers. In addition, methylation-specific protein binding patterns were observed for cg05575921 within AHRR, which had the highest level of detectable changes in DNA methylation associated with tobacco smoking (-24.40% methylation; p = 2.54E-182), suggesting a regulatory role for gene expression. The results of our study confirm the broad effect of tobacco smoking on the human organism, but also show that quitting tobacco smoking presumably allows regaining the DNA methylation state of never smokers.
Assuntos
Metilação de DNA/efeitos dos fármacos , Regulação da Expressão Gênica/efeitos dos fármacos , Genoma Humano/genética , Fumar/efeitos adversos , Adulto , Idoso , Fosfatase Alcalina/genética , Análise de Variância , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Ilhas de CpG/genética , Ensaio de Desvio de Mobilidade Eletroforética , Epigenômica/métodos , Feminino , Proteínas Ligadas por GPI/genética , Regulação da Expressão Gênica/genética , Genoma Humano/efeitos dos fármacos , Humanos , Isoenzimas/genética , Modelos Lineares , Masculino , Pessoa de Meia-Idade , Análise de Sequência com Séries de Oligonucleotídeos , Receptores de Trombina/genética , Proteínas Repressoras/genética , Fatores Sexuais , Abandono do Hábito de Fumar/estatística & dados numéricos , Fatores de TempoRESUMO
The Mre11/Rad50/Xrs2 (MRX) complex in Saccharomyces cerevisiae has well-characterized functions in DNA double-strand break processing, checkpoint activation, telomere length maintenance and meiosis. In this study, we demonstrate an involvement of the complex in the base excision repair (BER) pathway. We studied the repair of methyl-methanesulfonate-induced heat-labile sites in chromosomal DNA in vivo and the in vitro BER capacity for the repair of uracil- and 8-oxoG-containing oligonucleotides in MRX-deficient cells. Both approaches show a clear BER deficiency for the xrs2 mutant as compared to wildtype cells. The in vitro analyses revealed that both subpathways, long-patch and short-patch BER, are affected and that all components of the MRX complex are similarly important for the new function in BER. The investigation of the epistatic relationship of XRS2 to other BER genes suggests a role of the MRX complex downstream of the AP-lyases Ntg1 and Ntg2. Analysis of individual steps in BER showed that base recognition and strand incision are not affected by the MRX complex. Reduced gap-filling activity and the missing effect of aphidicoline treatment, an inhibitor for polymerases, on the BER efficiency indicate an involvement of the MRX complex in providing efficient polymerase activity.