Fig. 3. Usnic acid causes accumulation of an early nucleolar population of Nop7-TAP pre-ribosomes and depletion of late maturation factors.

Early pre-ribosomal particles were isolated via Nop7-TAP as bait from untreated cells (−) or after 2 min of 60 µM usnic acid (UA) treatment (+). a Nop7-TAP eluates were analyzed using SDS-PAGE following Coomassie staining or Western blot (MWM = molecular weight marker). b Samples from a were investigated by Northern blotting, detected (pre)-rRNA species are marked on the right, the probes used are indicated on the left, with their binding sites depicted in the scheme. c Quantitative mass spectrometry (qMS) was used to determine the relative changes in protein levels due to usnic acid treatment. Normalized abundances from usnic acid-treated cells were plotted against the control sample from untreated cells in the form of a scatter plot. Selected maturation factors that increase (above the diagonal) or decrease (below the diagonal) upon inhibitor treatment are indicated. The protein levels were normalized to the bait Nop7, and all proteins with an abundance of >0.1% (>0.001) relative to the bait in the untreated sample are shown. The means of two biological replicates for each factor are shown (n = 2) (Supplementary Data 1). d The fold change (log2 transformed values) of the qMS data (from c) for selected maturation factors (>0.01 abundance to bait) is shown for two biological replicates (n = 2; mean plus individual points shown). Source data are provided as a Source Data file.