FIG. 2.

Swi3 is required for survival of fork arrest. (A) Swi3 contributes to survival with UV irradiation in a rad13Δ uve1Δ strain that cannot excise UV damage. Cells of the indicated genotypes were spread on YES agar medium and exposed to the indicated dose of UV. Agar plates were incubated for 3 days at 30°C to measure UV survival. (B) Interaction of swi3Δ and chk1Δ mutations in UV survival assays indicates that Swi1 is required for tolerance of UV damage during DNA replication. Fivefold serial dilutions of cells were plated on YES agar medium and exposed to the indicated dose of UV. Agar plates were incubated for 2 to 5 days at 30°C. (C) Swi3 has a role in tolerating HU-induced fork arrest. swi3Δ cells were highly sensitive to HU. Synergistic interactions of swi3Δ with cds1Δ and chk1Δ mutations indicate that Swi3 has an HU survival function that is at least partially independent of Cds1 and Chk1. Fivefold serial dilutions of cells were incubated on YES agar medium supplemented with the indicated amounts of HU for 2 to 5 days at 30°C.