Investigating the effects of the presence of foreign DNA on DNA methylation and DNA repair events in cultured eukaryotic cells

Methylation of DNA in eukaryotic cells, global as well as gene-specific, is affected by endogenous and endogenous factors. In this paper, it is reported that deviations in DNA methylation and expression of genes involved in DNA repair and the cell cycle are affected in 143B cultured cells containing an expression vector. Global DNA methylation analysis with cytosine-extension assay revealed a decreased global DNA methylation in the presence of the expression vector. Less promoter-specific methylation, as measured by bisulfite-MS PCR, was observed for MGMT and p16INK4a in vector-containing cells. Comet assay investigations revealed a negative effect on the DNA repair capacity of both BER and NER in Complex III compromised cells. This was reflected in the down-regulation of hOGG1 and ERCC1 expression. The results presented in this paper support the existence of a strong relationship between impaired mitochondrial function and deviations in DNA methylation and extend this relationship to impaired DNA repair. ► Vector insertion in 143B cell line decreases DNA methylation in MGMT-gene promoter ► Altered DNA methylation of the p16INK4a-gene promoter observed ► Deviations in the stable gene expression due to a decrease in transgene mRNA ► Observed variation in promoter methylation may imply unstable protein expression. ► Foreign DNA insertion into genome of cultured cells manifest in their metabolism.