title: Respective role of each of the purine N7 nitrogens of 5'-O-triphosphoadenylyl(2'----5')adenylyl(2'----5')adenosine in binding to and activation of the RNase L of mouse cells.
abstract: Through a combination of chemical and enzymatic approaches a series of sequence-specific tubercidin-substituted ppp5'A2'p(5'A2'p)n5'A (n = 1 to about 10; 2-5A) analogues were generated. In addition to the previously developed methodology of Imai and Torrence [Imai, J., & Torrence, P.F. (1985) J. Org. Chem. 50, 1418-1420], a new approach to synthesis of 2',5'-linked oligonucleotides utilized adenosine in 3',5' linkage as a precursor to the targeted 5'-terminus of the desired product. For instance, A3'p5'A could be condensed under conditions of lead ion catalysis with tubercidin 5'-phosphate to give A3'p5'A2'p5'(c7A). Treatment with the 3',5'-specific nuclease P1 led to p5'A2'p5'(c7A). The combined use of the above procedures led to the synthesis of p5'(c7A)2'p5'A2'p5'A, p5'A2'p5'(c7A)2'p5'A, p5'A2'p5'A2'p5'(c7A), and p5'A2p5'(c7A)2'p5'(c7A), which were converted to their corresponding 5'-triphosphates by the usual methods. Evaluation of these analogues for their ability to bind to and activate the 2-5A-dependent endonuclease (RNase L) of mouse L cells showed that there were small changes (less than or equal to 10-fold) in the ability of the four tubercidin analogues to bind to RNase L. However, whenever the first and/or third adenosine nucleotide units were replaced by tubercidin, a dramatic decrease in ability to activate RNase L occurred. Only the second (from the 5'-terminus) adenosine residue could be replaced by tubercidin without any effect on RNase L activation ability.
mesh_terms: D000227:Adenine Nucleotides / Q000138:chemical synthesis* / Q000378:metabolism / Q000494:pharmacology; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D004722:Endoribonucleases / Q000378:metabolism*; D004789:Enzyme Activation; D007202:Indicators and Reagents; D007700:Kinetics; D007739:L Cells / Q000201:enzymology; D051379:Mice; D009841:Oligonucleotides / Q000138:chemical synthesis / Q000494:pharmacology; D009843:Oligoribonucleotides / Q000138:chemical synthesis* / Q000378:metabolism / Q000494:pharmacology; D043264:Phosphodiesterase I; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D011485:Protein Binding; D013379:Substrate Specificity; D014372:Tubercidin / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D000227:Adenine Nucleotides; D007202:Indicators and Reagents; D009841:Oligonucleotides; D009843:Oligoribonucleotides; C023505:2',5'-oligoadenylate; D004722:Endoribonucleases; C031956:2-5A-dependent ribonuclease; D000469:Alkaline Phosphatase; D010727:Phosphoric Diester Hydrolases; D043264:Phosphodiesterase I; D014372:Tubercidin