5‐azacytidine influences ATP synthase gene expression and ATP levels in Escherichia coli

Abstract

5‐azacytidine is a nucleoside analog that once incorporated into DNA, traps cytosine‐5 DNA methyltransferases and blocks further DNA methylation. Thus, 5‐azacytidine is commonly used as a DNA demethylating agent. We have performed gene expression DNA microarray analysis of E. coli cells treated with 5‐azacytidine to determine if cytosine DNA methylation influences gene expression. To our surprise, expression of all eight ATP synthase genes was up‐regulated in response to 5‐azacytidine. The effect was observed at early stationary phase, and not observed in logarithmic phase. To determine if cells treated with 5‐azacytidine have altered levels of ATP, we used a luciferase assay to measure ATP levels in untreated and 5‐azacytidine‐treated cells. The change in ATP levels in response to 5‐azacytidine is complex. At logarithmic phase, there are increased levels of ATP in 5‐ azacytidine‐treated cells, but this increase subsides as cells reach stationary phase. The increase in ATP levels in 5‐azacytidine‐treated cells at logarithmic phase was observed in a cytosine DNA methylation deficient strain (dcm knockout). These data indicate the model of DNA methyltransferase trapping cannot explain the changes in ATP levels, as this strain lacks a cytosine DNA methyltransferase. These data also indicate that 5‐azacytidine does not cause its effect on ATP metabolism through a loss of DNA methylation, and may occur via a novel mechanism. This work was supported by the Geneseo Foundation.