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Life without dUTPase

Fine-tuned regulation of the cellular nucleotide pools is indispensable for faithful replication of DNA. The genetic information is also safeguarded by DNA damage recognition and repair processes. Uracil is one of the most frequently occurring erroneous base in DNA; it can arise from cytosine deamination or thymine-replacing incorporation. Two enzyme families are primarily involved in keeping DNA uracil-free: dUTPases that prevent thymine-replacing incorporation and uracil-DNA glycosylases that excise uracil from DNA and initiate uracil-excision repair. Both dUTPase and the most efficient uracil-DNA glycosylase UNG is thought to be ubiquitous in free-living organisms. In the present work, we have systematically investigated the genotype of deposited fully sequenced bacterial and Archaeal genomes. Surprisingly, we have found that in contrast to the generally held opinion, a wide number of bacterial and Archaeal species lack the dUTPase gene(s). The dut- genotype is present in diverse bacterial phyla indicating that loss of this (or these) gene(s) has occurred multiple times during evolution. We have identified several survival strategies in lack of dUTPases: i) simultaneous lack or