2',5'-oligoadenylate synthetase in interferon-treated chick cells.

Chick embryo cells respond to interferon by producing very high levels of 2-5A synthetase. From inhibitor studies, it appears that the response involves the controlled derepression of an interferon-inducible gene. Continuous interaction of the cells with interferon seems to be necessary to maintain maximal enzyme induction. Partial purification of the synthetase indicates that it is probably composed of a single polypeptide of 56,000 MW. Upon activation by binding to dsRNA, this polypeptide catalyzes a nucleotidyl transferase reaction in which 5'-AMP residues are transferred from ATP to the 2' position of appropriate acceptors. A number of naturally occurring small molecules (in addition to 2-5A itself) that can function as adenylate acceptors have been identified, but the physiological significance of these adenylylation reactions remain to be established.