哺乳動物細胞におけるRNAの品質管理機構

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概要

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• 8-Oxo-7, 8-dihydroguanine (8-oxoGua) is generated in nucleic acids as well as in their precursors due to the actions of oxygen radicals produced through normal cellular metabolism. Since oxidized guanine can pair with both cytosine and adenine, it causes alterations in the phenotypic expression when it is present in RNA. To prevent such an outcome, organisms must have some mechanism for eliminating the oxidized guanine from RNA and its precursors. (1) In the precursor level, human MTH1 and NUDT5 proteins degrade 8-oxoGTP and 8-oxoGDP to 8-oxoGMP, which is an unusable form for RNA synthesis. Expression of the cDNA (NUDT5 or MTH1) in the E. coli mutT mutant reduced the level of production of erroneous proteins to the wild type one. These results clearly indicate that the elimination of 8-oxoGua-containing ribonu-cleotides from the precursor pool is important to secure accurate protein synthesis. (2) At the RNA level, the E. coli polynucleotide phosphorylase (Pnp) protein has been identified as being a good candidate for such a role. The protein has a specific binding activity to 8-oxoguanine-containing RNA. The mutants defective in the protein are hyperresistant to paraquat, a drug that induces oxidative stress in the cell. A human homologue (PNP) protein has the ability to bind specifically to 8-oxoGua-containing RNA. When human cells are exposed to agents that induce oxidative stress, amounts of the human protein decrease rapidly while amounts of other proteins in the cells do not change after such treatments. These results imply that the human proteins might thus play a role in excluding oxidized forms of RNA from cells.

• 2007-09-30

著者

• 早川 浩

  福岡歯科大学機能生物化学講座生化学分野

• 早川 浩

  福岡歯大・生化学分野

関連論文

• 哺乳動物細胞におけるRNAの品質管理機構
• A-1 アクチナーゼE標品からのトリプシンおよびキモトリプシン様酵素の単離・精製とそれらの物理化学的,酵素化学的性質(一般口演1,第34回福岡歯科大学学会総会抄録)
• 福岡歯科大学アニマルセンター紹介

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