Δabp1 is not sensitive to hydroxyurea treatment. Cells were plated on YEA plates containing the indicated concentrations of hydroxyurea (HU) and incubated for 5 days at 32°C. Each row represents a sequential five-fold serial dilution of the initial plating of 105 cells. The control strain Δcds1 looses viability at very low concentrations of HU (2.5 mM) and fails to form colonies at the higher concentrations of 5 and 10 mM HU. Cds1 is essential for the intra-S phase checkpoint activated in response to replication blocks . In contrast, wildtype (wt) or Δabp1 display similar sensitivity to HU that is only observed at the highest concentration of 10 mM.