Structural organization, evolution, and distribution of viral pyrimidine dimer-DNA glycosylases

DNA glycosylases are DNA repair enzymes capable of removing damaged nitrogenous bases, including those formed as a result of UV irradiation with sunlight (approximately 300–400 нм). DNA glycosylases are common not only among bacteria, archaea, and eukaryotes, but some groups of viruses can also encode them. The best-known viral glycosylase is endonuclease V (DenV, Pdg-T4) of Escherichia virus T4, the main substrate of which is cyclobutane pyrimidine dimers. DenV is isolated separately from other large families of glycosylases; it is quite common in nature and has homologs in a number of other viruses and even bacteria. However, the ways of its origin are poorly understood. The best-known DenV homolog is the glycosylase of Chlorella virus strain, PBCV-1 (Cv-pdg). This review contains the main known data on the structure and mechanism of operation of DenV and its homologs. The issues of biological importance and distribution of the enzyme and its homologs among viruses are considered and supplemented separately.