Degradation of nucleic acids with ozone. III. Mode of ozone-degradation of mouse proline transfer ribonucleic acid (tRNA) and isoleucine tRNA.

Abstract

The degradation of mouse [32P]proline transfer ribonucleic acid (tRNA) and [32P]isoleucine tRNA with ozone (concentration in inlet gas, 0.1 mg/l) was examined in aqueous solution (reaction time, 0-32 min) and sequence analysis of the products was performed by digestion with ribonuclease A or T1 according to Sanger's method. The guanine moieties in the nucleobases were preferentially attacked by ozone and the cleavage of polynucleotidic linkages did not occur during the ozonization. Proline tRNA was more degradable than isoleucine tRNA, probably as a result of differences in the locations of the guanine residues in their higher-order structures. The consecutive guanine residues in the anticodon and dihydrouracil (D) regions of proline tRNA were most susceptible to degradation with ozone. In the case of isoleucine tRNA, which does not have the conseutive guanine residues in the anticodon region, those in the D-loop, small (S) loop and the common stem were degraded. Therefore ozone seems to start reacting with the guanine moieties located in the most exposed regions of the higher-order structure of tRNA.