https://pmc.ncbi.nlm.nih.gov/articles/PMC52931/
Possible involvement of (2'5')oligoadenylate synthetase activity in pre-mRNA splicing - PMC
The first step in splicing of pre-mRNA involves an intermediate lariat structure, in which a 2'5' phosphodiester bond between the 5' terminal guanosine residue...
2 5 oligoadenylate synthetase