[1] It also synthesizes long, highly heteropolymeric tails in vivo.

[1] Discovered by Marianne Grunberg-Manago working in Severo Ochoa's lab in 1955, the RNA-polymerization activity of PNPase was initially believed to be responsible for DNA-dependent synthesis of messenger RNA, a notion that was disproven by the late 1950s.

[3][4] It is involved in mRNA processing and degradation in bacteria, plants,[5] and animals.

The protein is present in bacteria and in the chloroplasts[2] and mitochondria[7] of some eukaryotic cells.

[7] The same abbreviation (PNPase) is also used for another, otherwise unrelated enzyme, Purine nucleoside phosphorylase.