Exposure of eukaryotic cells to ionizing radiation or clastogenic chemicals leads to formation of DNA double-strand breaks (DSBs). These lesions are also generated internally by chemicals and enzymes, in the absence of exogenous agents, though the sources and consequences of such endogenously generated DSBs remain poorly understood. In the current study, we have investigated the impact of reduced recombinational repair of endogenous DSBs on stress responses, cell morphology and other physical properties of S. cerevisiae (budding yeast) cells. Use of phase contrast and DAPI-based fluorescence microscopy combined with FACS analysis confirmed that recombination-deficient rad52 cell cultures exhibit chronically high levels of G2 phase cells. Cell cycle phase transit times during G1, S and M were similar in WT and rad52 cells, but the length of G2 phase was increased by three-fold in the mutants. rad52 cells were larger than WT in all phases of the cycle and displayed other quantifiable changes in physical characteristics. The high G2 cell phenotype was abolished when DNA damage checkpoint genes, but not spindle assembly checkpoint genes, were co-inactivated with RAD52. Several other RAD52 group mutants (rad51, rad54, rad55, rad57 and rad59) also exhibited the high G2 cell phenotype. The results indicate that recombination deficiency leads to accumulation of unrepaired DSBs during normal mitotic growth that activate a major stress response and produce distinct changes in cellular physiology and morphology.
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| Gene | Phenotype | Experiment Type | Mutant Information | Strain Background | Chemical | Details |
|---|---|---|---|---|---|---|
| RAD52 | bud morphology: abnormal | classical genetics | null Allele: rad52-Δ | S288C | Details: ~3-fold more cells with extra buds than in wt cultures | |
| RAD52 | cell cycle progression in G2 phase: increased duration | classical genetics | null Allele: rad52-Δ | S288C | Details: 94% of the large-budded cells are in G2 phase in the null mutant, compared to 75% in wt cells; length of G2 phase increases from 18 min in wt cells to 59.9 min in the null mutant | |
| RAD52 | cellular morphology: abnormal | classical genetics | null Allele: rad52-Δ | S288C | Details: 2-fold increase in large-budded (average 1.5 μm larger than wt) cells relative to wt | |
| RAD52 | cellular morphology: abnormal | homozygous diploid | null Allele: rad52-Δ | S288C | Details: 2-fold increase in large-budded cells in the homozygous diploid null mutant relative to wt | |
| RAD51 | cellular morphology: abnormal | classical genetics | null Allele: rad51-Δ | S288C | Details: increased percentage of cells with a large bud morphology | |
| RAD54 | cellular morphology: abnormal | classical genetics | null Allele: rad54-Δ | S288C | Details: increased percentage of cells with a large bud morphology | |
| RAD55 | cellular morphology: abnormal | classical genetics | null Allele: rad55-Δ | S288C | Details: increased percentage of cells with a large bud morphology | |
| RAD57 | cellular morphology: abnormal | classical genetics | null Allele: rad57-Δ | S288C | Details: increased percentage of cells with a large bud morphology | |
| RAD59 | cellular morphology: abnormal | classical genetics | null Allele: rad59-Δ | S288C | Details: increased percentage of cells with a large bud morphology | |
| RAD57 | growth in exponential phase: decreased rate | classical genetics | null Allele: rad57-Δ | S288C | Details: null mutants have a doubling time of 92.1 minutes compared to 83.0 minutes in wt cells |
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.