Figure 5. Pulse–chase analysis of RNA from Δnop53 cells (A) or from cells depleted of Nop53p (B).

(A) RNA from WT and Δnop53 cells was metabolically labelled with [³H]uracil for 1 min followed by a chase with excess of unlabelled uracil for 1, 5, 15 and 30 min (noted above each lane). For each lane, RNA corresponding to 50000 c.p.m. of the starting material was separated on a 1.3% (v/v) formaldehyde-agarose gel before autoradiography. (B) Δnop53 cells expressing pGAL-NOP53 were grown in either galactose or glucose for 14 h before pulse–chase analysis. The major rRNA species are marked. Cells lacking Nop53p exhibit defects in 27 to 25 S processing as indicated by the absence of labelled 25 S rRNA and accumulation of the larger 35 and 27 S precursor species.