Translational regulation of ribonucleotide reductase by eukaryotic initiation factor 4E links protein synthesis to the control of DNA replication.
Ribonucleotide reductase synthesizes dNDPs, a specific and limiting step in DNA synthesis, and can participate in neoplastic transformation when overexpressed. The small subunit (ribonucleotide reductase 2 (RNR2)) was cloned as a major product in a subtraction library from eukaryotic initiation factor 4E (eIF4E)-transformed cells (Chinese hamster ovary-4E (CHO-4E)). CHO-4E cells ... have 20-40-fold elevated RNR2 protein, reflecting an increased distribution of RNR2 mRNA to the heavy polysomes. CHO-4E cells display an altered cell cycle with shortened S phase, similar to cells selected for RNR2 overexpression with hydroxyurea. The function of ribonucleotide reductase as a checkpoint component of S progression was studied in yeast in which elevated eIF4E rescued S-arrested rnr2-68(ts) cells, by increasing recruitment of its mRNA to polysomes. Crosses between rnr2-68(ts) and mutant eIF4E (cdc33-1(ts)) engendered conditional synthetic lethality, with extreme sensitivity to hydroxyurea and the microtubule depolymerizing agent, benomyl. The double mutant (cdc33-1 rnr2-68) also identified a unique terminal phenotype, arrested with small bud and a randomly distributed single nucleus, which is distinct from those of both parental single mutants. This phenotype defines eIF4E and RNR2 as determinants in an important cell cycle checkpoint, in early/mid-S phase. These results also provide a link between protein and DNA synthesis and provide an explanation for cell cycle alterations induced by elevated eIF4E.
Mesh Terms:
Animals, Benomyl, CHO Cells, Cell Cycle, Cloning, Molecular, Cricetinae, DNA Replication, Eukaryotic Initiation Factor-4E, Fibroblast Growth Factors, Gene Expression Regulation, Hydroxyurea, Microtubules, Ornithine Decarboxylase, Peptide Initiation Factors, Polyribosomes, Protein Biosynthesis, RNA, Messenger, Recombinant Proteins, Ribonucleotide Reductases, S Phase, Saccharomyces cerevisiae, Transcription, Genetic, Transfection
Animals, Benomyl, CHO Cells, Cell Cycle, Cloning, Molecular, Cricetinae, DNA Replication, Eukaryotic Initiation Factor-4E, Fibroblast Growth Factors, Gene Expression Regulation, Hydroxyurea, Microtubules, Ornithine Decarboxylase, Peptide Initiation Factors, Polyribosomes, Protein Biosynthesis, RNA, Messenger, Recombinant Proteins, Ribonucleotide Reductases, S Phase, Saccharomyces cerevisiae, Transcription, Genetic, Transfection
J. Biol. Chem.
Date: Dec. 10, 1999
PubMed ID: 10585489
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