Fig. 4. Cell cycle delay caused by high levels of Tel1 involves Rad53, Rad9 and Chk1. Strains were as follows: wild type (K699), GAL1–TEL1 (DMP3539/10D), rad9Δ (YLL157), GAL1–TEL1 rad9Δ (DMP3575/6B), rad53K227A (DMP3479/2A), GAL1–TEL1 rad53K227A (DMP3479/2B), GAL1–TEL1 chk1Δ (DMP3611/6D) and GAL1–TEL1 rad53K227A chk1Δ (DMP3611/3B). (A and B) Cell cultures growing logarithmically in YEP-raf were synchronized in G₁ with α-factor in the presence of galactose (2 h) and released from the α-factor block at time zero in YEP-raf-gal or were UV irradiated (40 J/m²) prior to release in YEP-raf-gal. Samples were collected at the times indicated after α-factor release to analyze the DNA content of untreated (top) and UV-treated (bottom) cell cultures by FACS (A) and to score the untreated cell cultures for the percentage of binucleate cells by propidium iodide staining (B). (C) Serial dilutions of YEP-raf exponentially growing cell cultures were spotted on YEP-raf-gal plates with or without MMS. One YEP-raf-gal plate was UV irradiated (UV).