NAM inhibits the completion of DNA replication in slx4Δ and pph3Δ mutants. (A) NAM-induced S-phase arrest in slx4Δ and pph3Δ mutants depends on Rad9 and Rtt109. Exponentially growing cells were incubated in YPD with 20 mM NAM and samples were taken at the indicated time points for DNA content analysis by flow cytometry. (B–C) Rad53-dependent inhibition of the activation of late DNA replication origins contributes to growth defects of slx4Δ and pph3Δ in NAM. (B) Cells were grown in 96 well plates and OD readings were acquired as described in Materials and Methods. (C) Cells were treated as in A. 1n, 2n: DNA content.