|Budget Amount *help
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2002: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2001: ¥2,000,000 (Direct Cost: ¥2,000,000)
Previosly we found that the persistence of oxidized guanine residues in messenger RNA caouses translational errors in Eschericha coli cells and, as the result, abnormal protein is produced [Science 278, 128-130. 1997]. To counteract, organisms possess a mechanism to prevent misincorporation of 8-oxoguanine, an oxidized form of guanine residue, into nascent RNA. E. coli MutT protein hydrolyzes 8-oxoGTP, an oxidized GTP as substrate for erroneous RNA synthesis, thereby suppressing the misincorporation. However, when guanine residues in RNA are oxidized, the mechanism is totally useless. One can, therefore, assume that organisms probably have another mechanism for recognizing RNA molecules carrying 8-oxoguanine and prevent the RNA from entering into the cellular translation machinery.
In this present project we found that E. coli and human cells possess proteins that bind specifically to RNA containing 8-oxoguanine. PNP protein of E. coli (Biochemistry 2001) and YB-1 proteins of human (Biochemistry 2002) are identified as such binding proteins. E. coli mutants defective in the enzyme become super-resistant to paraquat, a well-known drug inducing oxidative stress. These proteins may function to discriminate oxidized and normal RNA molecules, this maintaining a high fidelity of translation.