Fig. 8. Actinomycin D (Act. D) and L-mimosine failed to induce G1 arrest in HeLa and revertants. Unsynchronized cells were treated with actinomycin D (A) or L-mimosine (B) for 24 h at a concentration of 1 nM and 250 µM, respectively. Cell cycle analysis was performed as described in "Materials and Methods." Fibroblasts and the BICR mammary carcinoma cell line were used as positive controls for actinomycin D and L-mimosine treatments, respectively.