Genetic requirements for lacO-dependent Chk1 phosphorylation.

* indicates phospho Chk1. A. The phosphorylation status of Chk1 was detected with α-HA over 24 hours following induction of Rad3-GFP/LN in lacO positive cells in the genetic background indicated. Increased time is indicated by the wedge. B. Equivalent experiments assessing Chk1 phosphorylation in rad⁺lacO positive cells upon induction of the indicated constructs. C. Chk1 phosphorylation was assessed upon expression of Rad3-GFP/LN in the indicated genetic backgrounds at t = 22 hours. D. The phosphorylation status of Chk1 was assessed following induction of Rad3-GFP/LN in lacO positive cells in rad⁺ and the indicated double mutant where H2A cannot be phosphorylated. E. The indicated constructs were expressed in rad⁺ or rad9-T412 cells and Chk1 phosphorylation monitored. Rad9 T412 phosphorylation is required for the interaction of 9-1-1 complex with Rad4^TopBP1.