Figure 3.

Downregulation of SENP3 interferes with pre-ribosomal RNA processing. (A) Diagram summarizing the main steps of rRNA processing. (B,C) HeLa cells were transfected with siRNA duplexes targeting NPM1, SENP5 or SENP3, as indicated. Transfection of a scrambled oligonucleotide served as a control. At 72 h after transfection, cells were pulse labelled with ³²P-orthophosphate for 1 h and chased for 2 h. An equal amount of RNA was loaded into each lane. Ethidium bromide (EtBr) staining of 28S and 18S rRNA is shown. Downregulation of the respective proteins was analysed by western blotting. (D) The signal intensities of the 28S and 32S rRNA forms were quantified by phosphoimager analysis and the 28S:32S ratio was calculated. ETS, external transcribed spacer; ITS, internal transcribed spacer; NPM1, nucleophosmin; siRNA, short interfering RNA.