The human 2¢)5¢ oligoadenylate synthetases (OAS) form a conserved family of interferon-induced proteins consisting of four genes:OAS1, OAS2, OAS3and the 2¢)5¢ oligo-adenylate synthetase-like gene (OASL). When activated by double-strandedRNA,OAS1–3polymerizeATP into2¢)5¢-linkedoligoadenylates; 2¢)5¢-linkedoligoadenylates, in turn, activate a latent endoribonuclease that degrades viral and cellular RNAs. In contrast, while the p59 OASLprotein is highlyhomologous to theOAS family (45%identity), its 350 amino acid N-terminal domain lacks 2¢)5¢ oligoadenylate synthetase activity. .
