Figure 2.—

The Rad32–Rad50–Nbs1 complex is required for full S-phase DNA damage checkpoint activation during replication in response to MMS. (A) nbs1 mutation reduces checkpoint signaling in response to MMS. nbs1Δ (yFS267, n = 8, G1 enrichment range 28–91%) mutants display reduced Cds1 kinase activity relative to wild-type (yFS162, n = 8, G1 enrichment range 54–92%) cells in response to MMS. rad3Δ (yFS260, n = 1) cells display a complete defect in Cds1 activity in response to DNA damage. (B) nbs1Δ (yFS267, n = 6, G1 enrichment range 47–91%) mutants display proficient checkpoint signaling relative to wild-type (yFS162, n = 8, G1 enrichment range 70–94%) cells in response to HU arrest. The MMS data is from A. Signal was normalized within each experiment to the 120-min MMS-treated wild-type culture. Representative raw data and G1 enrichment is shown.