2,6-Diaminopurine

2,6-diaminopurine (2,6-DAP, also known as 2-aminoadenine) is a compound once used in the treatment of leukemia. It is found instead of adenine in the genetic material of some bacteriophage viruses.
In August 2011, a report, based on NASA studies with meteorites found on Earth, was published suggesting 2,6-diaminopurine and related organic molecules, including the DNA and RNA components adenine and guanine, may have been formed extraterrestrially in outer space.
Cyanophage S-2L.
In cyanophage S-2L, diaminopurine is used instead of adenine (host evasion). Diaminopurine base (Z) pairs perfectly with thymine (T) as it is identical to adenine (A) but has an amine group at position 2 forming 3 intramolecular hydrogen bonds, eliminating the major difference between the two types of basepairs (weak:A-T and strong:C-G). This improved stability affects protein-binding interactions that rely on those differences.
4 papers published together in 2021 
identify and describe proteins encoded by cyanophage S-2L and similar viruses that help synthesis and use diaminopurine.