Fig. 2

Controls for nucle(ol)ar accumulation of GFP-tagged ribosomal reporter proteins upon inhibitor treatment. Numbers in brackets denote the unique identifier of the compounds listed in Additional file 3: Table S3. a 60S subunit reporter Rpl7a-GFP. In the untreated cells, Rpl7a-GFP was exclusively localized in the cytoplasm, as is typical for ribosomal proteins due to the high concentration of mature ribosomes in the cytoplasm. Acivicin was discovered in the course of the 60S screen and causes nucleolar accumulation (indicated by white arrowheads) of the 60S reporter, suggesting a very early block in ribosome biogenesis. Treatment with diazaborine specifically blocks 60S maturation, resulting in nuclear accumulation of Rpl7a-GFP. b 40S subunit reporter Rps9a-GFP. While Rps9a-GFP was found exclusively in the cytoplasm in the untreated cells, it accumulated in the nucleolus upon treatment with acivicin (indicated by white arrowheads)