The (2'-5')oligoadenylate synthetase is present in the lowest multicellular organisms, the marine sponges. Demonstration of the existence and identification of its reaction products.

We have proved the presence of (2'-5')oligoadenylates [(2'-5')An] and oligoadenylate synthetase [(2'-5')An synthetase] in the marine sponge Geodia cydonium. (2'-5')An isolated from sponge crude extract competed with authentic (2'-5')An for binding to polyclonal antiserum against (2'-5')An. HPLC analysis revealed the presence of nucleotides eluting with molecular markers for (2'-5')A oligomers. The biological activity of sponge (2'-5')An was demonstrated by inhibiting the protein biosynthesis in rabbit reticulocyte lysate. The activity of the (2'-5')An synthetase, present in crude sponge extract, was found to be high compared to that in mammalian interferon-treated cell extract. The (2'-5')An synthetase from sponge extract binds to poly(I).poly(C) as does the mammalian enzyme. Western blot analysis with antibodies to recombinant rat 43-kDa (2'-5')An synthetase revealed in sponge immunologically related proteins with molecular masses of approximately 110, 65, 61 and 34 kDa. We conclude, that the (2'-5')An system has evolved from receptors and enzymes involved in cell adhesion and/or growth control.