Dissection of the Roles of Adenine Ring Nitrogen (N-1) and Exocyclic Amino (N-6) Moieties in the Interaction of 2-5A with RNase L

Abstract

To elucidate further the roles played by the adenine bases in the interaction of RNase L (EC 3.1.2.6) with the 2′ ,5′ -oligoadenylate 2-5A, p5′A2′(p5′A2′)np5′ A, a series of sequence-specific 1-deazaadenosine (c1A)-substituted analogues were synthesized and evaluated for their ability to bind to and activate human RNase L in comparison to earlier reported inosine-substituted congeners of 2-5A. Substitution of only the 5′ -terminal adenosine of p5′A2′p5′A2 p5 A with c1A afforded an analogue with strongly diminished RNase L binding and activation ability, while replacement of the second or middle adenosine of p5 A2′ p5′A2′p5′ A had only a modest effect. In distinct contrast to p5′A2′p5′A2′p5′I, the c1A analogue with the third or 2′ -terminal adenosine replacement approached parent p5′ A2′p5′A2′p5′ A in RNase L activation ability. These results permitted a further dissection of the role of various nucleotidic functional groups in the interaction of 2-5A with RNase L: specifically, that the 5′ -terminal adenosine purine N-1 moiety is key for binding to RNase L, while the 2′ -terminal adenosine N-6 exocyclic amino group is critical for RNase L activation.