Maintenance of mitochondrial DNA by the Caenorhabditis elegans ATR checkpoint protein ATL-1

Here we show that inactivation of the ATR-related kinase ATL-1 results in a significant reduction in mitochondrial DNA (mtDNA) copy numbers in Caenorhabditis elegans. Although ribonucleotide reductase (RNR) expression and the ATP/dATP ratio remained unaltered in atl-1 deletion mutants, inhibition of RNR by RNAi or hydroxyurea treatment caused further reductions in mtDNA copy number. These results suggest that ATL-1 functions to maintain mtDNA independently of RNR.