Figure 5.

Sensitive but not resistant cells transit through mitosis in the presence of ABHA. (A–C) Cells were synchronized at G1/S by overnight treatment with hydroxyurea (HU) and then released from the arrest and treated without (Con) or with 100 μg/ml ABHA (ABHA) 2 h after release. Cells were harvested at the indicated times after release and analyzed by FACS for their cell cycle status as in Figure 1. The 8-h control time point is shown as a measure of the synchrony obtained. The data presented are representative of three to five separate experiments. Identical data were obtained using 100 ng/ml TSA in place of ABHA (our unpublished results). (D) The activity of cyclin A/cdk2 and cyclin B1/cdc2 was assessed by anti-cdk2 and anti-cyclin B1 immunoprecipitate kinase assays from samples of the indicated cell lines harvested at 12 h after release from a hydroxyurea block and treated without or with 100 μg/ml ABHA as in A–C. The autoradiogram of the phosphorylated histone H1 and activity expressed as percentage of the control for each cell line are shown.