Yeast Mre11 and Rad1 Proteins Define a Ku-Independent Mechanism To Repair Double-Strand Breaks Lacking Overlapping End Sequences
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FIG. 1.HO cleavage sites in the MAT locus of chromosome III in SLY18 and SLY19. After HO endonuclease induction, two complementary breaks are generated in SLY18, whereas in SLY19, noncomplementary breaks will be formed. The locations of primers that were used for PCR amplification and sequence analysis of the repair junctions from survivors are indicated by arrows.
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FIG. 2.Epistasis analyses of the effects of RAD1, RAD52, and YKU70 on gamma-ray hypersensitivity. Logarithmic cultures of yeast cells were harvested and resuspended in phosphate-buffered saline, plated onto YEP-dextrose media, and irradiated with the indicated dose of gamma rays. After 3 to 4 days of growth, surviving colonies were counted, and the survival rate was calculated by comparison to the number of colonies from the mock-treated cells. The percentages of survival of RAD+ (solid circles), rad1Δ (open diamonds), yku70Δ (solid diamonds), rad52Δ (open squares), rad52Δ yku70Δ (solid triangles), rad1Δ rad52Δ (open circles), rad14Δ rad52Δ yku70Δ (open triangles), and rad1Δ rad52Δ yku70Δ (solid squares) cells are shown. Each experimental point represents the average of three independent experiments.
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FIG. 3.Model for MMEJ. Shown is the joining event that is the most frequent in SLY19. Putative end processing of 4-bp 3′ noncomplementary overhangs created by the cleavage of two HO endonuclease recognition sequences will expose the microhomology that mediates annealing. Subsequent 3′-flap removal that is mostly dependent on Rad1-Rad10 will prime the fill-in synthesis and ligation by Dnl4. Microhomologies are shown in boldface. Unpaired 3′ flaps are shown as small letters. The gene products that may function at each step are listed to the right of the arrows.
- American Society for Microbiology
