he latest research by Philippe marliere research group of Paris sackle University reveals the atypical DNA synthesis based on aminoadenine sipoviruses. This research result was published in science recently. Phage genomes contain a wide range of nuclear base chemical diversity in all life forms. Some DNA viruses (such as cyanobacteria, Proteobacteria and actinomycetes) infecting the host have the phenomenon that aminoadenine completely replaces adenine, thus forming three hydrogen bonds with thymine, which violates the Watson Crick pairing rule. Aminoadenine encodes a DNA polymerase homologous to the Klenow fragment of bacterial DNA polymerase I, which contains 3-exonuclease but lacks 5-exonuclease activity. It has been found that aminoadenine is preferentially used instead of adenine in the incorporation of thymine based deoxynucleoside triphosphate. The polymerase gene occurs simultaneously with the gene of a biosynthetic enzyme, which produces aminoadenine deoxynucleotides in various sword spore virus phages. Phylogenetic clustering of polymerase and biosynthetic enzymes indicates that aminoadenine and adenine have been accompanied by DNA replication since ancient times.
