Dactinomycin : rbd-1
"The amount of Ct-RBD-1 was very much reduced in the nucleolus, 1 h after the addition of actinomycin D (compare Figure 6, A and B)... After 3 h of actinomycin D treatment, the changes were more accentuated and the nucleolus was almost devoid of Ct-RBD-1 (Figure 6C). In phase contrast, the nucleolus was still detectable after both 1 and 3 h. Ct-RBD-1 is therefore only present in the nucleolus when pre-rRNA is synthesized."