Fig. 5.

Rad3^ATR regulates ade6 recombination in an Exo1-dependent manner. (A) Schematic representation of the ade6 recombination system. Recombination between the ade6 heteroalleles can occur by conversion (lower left) or deletion (lower right) pathways. White and black circles represent the mutations in the ade6 open reading frames. (B) ade6 recombination frequency was scored in the indicated strains following 48 hours of growth either with or without thiamine (fork arrest ‘off’ and ‘on’, respectively). Cells were plated onto adenine-deficient medium containing thiamine at baseline (T0). wt, wild-type control. Data show the mean±s.d. (three independent experiments). (C) Simplified schematic indicating that Rad3^ATR, Rad26^ATRIP (R3, R26) and the 9-1-1 complex regulate Exo1 to reveal ssDNA, which associates with RPA and recombination proteins [e.g. Rad52 (52)] when the replisome (Rep) is no longer competent.