Northern blot analysis of pre-rRNAs detected by using probes complementary to the 5′-ETS and ITS1. ( A ) Northern blot using probe P1 complementary to the 5′-ETS upstream site A0. ( B ) Northern blot using probe P2 complementary to the 5′-ETS downstream site A0. ( C ) Northern blot using probe P3 complementary to ITS1 upstream site 2c. ( D ) and ( E ) Northern blots using probes P1 and P3 of longer electrophoresis runs. ( F ) Northern blot of cells treated with leptomycin B using probe P3 complementary to ITS1 upstream site 2c. ( G ) Structure of the 47S pre-rRNA and pre-rRNA intermediates that are most affected in NIP7-depleted cells. The positions of the probes P1, P2 and P3 used in the northern blots shown in A–D are indicated. HEK293, parental cells; SC, cells transfected with the scrambled shRNA; CP4, cells transfected with shRNA against the NIP7 mRNA.