Fig. 4.

Sirtuin 7 protein is involved in the cleavage at site 2. (A) Presentation of the pre-rRNAs mentioned in this manuscript. Arrowheads indicate the endonucleolytic sites. Asterisks indicate the position of the ETS (in red) and 5.8S+ (in blue) probes. The reactivity of both probes with each pre-rRNA is given on the right (+ or −). (B,C) Total RNAs were prepared from HeLa cells transfected with control siRNAs, or with siRNAs targeting sirtuin 7 or siRNAs targeting fibrillarin or siRNAs targeting both proteins. RNAs were separated by electrophoresis in a gel (EtBr) as two series, which were blotted and each series hybridized with the ETS probe (B) or with the 5.8S+ probe (C). To better appreciate the different bands revealed by the 5.8S+ probe, short and long exposures are presented and some bands are highlighted by asterisks. The 45S pre-rRNA corresponds to the lower band of the doublet observed in the upper part of the northern blot. The white spaces apparent in B and C correspond to the removal of the same lane from both series at the level of the gel and blot.