Crt1 Background Information DNA damage results in the arrest of cell cycle progression, allowing the damaged DNA to be repaired prior to replication. Checkpoints exist at several cell cycle phase transitions to maintain this genetic integrity. Rad9, Rad17, Rad24 and Mec3 are involved in activating the G1 and G2 checkpoints (1-4). Pol2 (also known as Dun2), encoding the catalytic subunit of DNA polymerase epsilon, plays a role in activating the S phase checkpoint (5). The protein kinase Rad53 (also designated Spk1, Mec2 or Sad1) is essential for both G2 and S phase arrest (6). Crt1, a DNA-binding protein that functions to recruit general repressors to the promoters of
damage-inducible genes, is activated by DNA damage (7). Phosphorylation of Hct1, a regulator of APC function, provides a mechanism by which Cdc28 blocks its own inactivation during S phase and early mitosis (8).
