Fidelity in DNA replication and repair requires adequate and balanced deoxyribonucleotide pools that are maintained primarily by regulation of ribonucleotide reductase (RNR). RNR is controlled via transcription, protein inhibitor association, and subcellular localization of its two subunits, R1 and R2. Saccharomyces cerevisiae Sml1 binds R1 and inhibits its activity, while Schizosaccharomyces pombe Spd1 impedes RNR holoenzyme formation by sequestering R2 in the nucleus away from the cytoplasmic R1. Here we report the identification and characterization of S. cerevisiae Dif1, a regulator of R2 nuclear localization and member of a new family of proteins sharing separate homologous domains with Spd1 and Sml1. Dif1 is localized in the cytoplasm and acts in a pathway different from the nuclear R2-anchoring protein Wtm1. Like Sml1 and Spd1, Dif1 is phosphorylated and degraded in cells encountering DNA damage, thereby relieving inhibition of RNR. A shared domain between Sml1 and Dif1 controls checkpoint kinase-mediated phosphorylation and degradation of the two proteins. Abolishing Dif1 phosphorylation stabilizes the protein and delays damage-induced nucleus-to-cytoplasm redistribution of R2. This study suggests that Dif1 is required for nuclear import of the R2 subunit and plays an essential role in regulating the dynamic RNR subcellular localization.
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| Gene | Phenotype | Experiment Type | Mutant Information | Strain Background | Chemical | Details |
|---|---|---|---|---|---|---|
| DIF1 | protein/peptide distribution: abnormal Reporter: ribonucleotide reductase subunit R2 Rnr2p and Rnr4p | classical genetics | null Allele: dif1-Δ | Other | Details: decreased percentage of cells with a predominantly nuclear localization pattern of Rnr2p and Rnr4p, relative to wild type cells | |
| DIF1 | protein/peptide distribution: abnormal Reporter: Rnr2p | classical genetics | overexpression | Other | Details: increased percentage of cells in which Rnr2p is predominantly nuclear localized, relative to wild type cells | |
| WTM1 | protein/peptide distribution: abnormal Reporter: Rnr4p | classical genetics | null Allele: wtm1-Δ | Other | Details: decreased nuclear localization relative to wild type cells | |
| KAP122 | protein/peptide distribution: abnormal Reporter: Rnr4p | classical genetics | null Allele: kap122-Δ | Other | Details: decreased nuclear localization relative to wild type cells |
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Increase the total number of rows showing on this page by using the pull-down located below the table, or use the page scroll at the table's top right to browse through the table's pages; use the arrows to the right of a column header to sort by that column; filter the table using the "Filter" box at the top of the table; click on the small "i" buttons located within a cell for an annotation to view further details about experiment type and any other genes involved in the interaction.
| Evidence ID | Analyze ID | Interactor | Interactor Systematic Name | Interactor | Interactor Systematic Name | Allele | Assay | Annotation | Action | Phenotype | SGA score | P-value | Source | Reference | Note |
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Increase the total number of rows showing on this page by using the pull-down located below the table, or use the page scroll at the table's top right to browse through the table's pages; use the arrows to the right of a column header to sort by that column; filter the table using the "Filter" box at the top of the table; click on the small "i" buttons located within a cell for an annotation to view further details about experiment type and any other genes involved in the interaction.