Progress on Z genome biosynthetic pathway of bacteriophage.

There are abundant base modifications in bacteriophages' genomes, mainly for avoiding the digestion of host endonucleases. More than 40 years ago, researchers discovered that 2-amino-adenine (Z) completely replaced adenine (A) and forms a complementary pairing with three hydrogen bonds with thymine (T) in the DNA of cyanophage S-2L, forming a distinct "Z-genome". In recent years, researchers have discovered and validated the biosynthetic pathway of Z-genome in various bacteriophages, constituting a multi-enzyme system. This system includes the phage-encoded enzymes deoxy-2'-aminoadenylosuccinate synthetase (PurZ), deoxyadenosine triphosphate hydrolase (dATPase/DatZ), deoxyadenosine/deoxyguanosine triphosphate pyrophosphatase (DUF550/MazZ) and DNA polymerase (DpoZ). In this review, we provide a concise overview of the historical discovery on diversely modified nucleosides in bacteriophages, then we comprehensively summarize the research progress on multiple enzymes involved in the Z-genome biosynthetic pathway. Finally, the potential applications of the Z-genome and the enzymes in its biosynthetic pathway are discussed in order to provide reference for research in this field.