The structure of 5.8S rRNA in preribosomes is altered in the absence of L19. (A) In vivo structure probing of 5.8S rRNA (SHAPE) was conducted by treating cells with NAI and assaying modified nucleotides via primer extension with an oligonucleotide complimentary to the 5′ half of ITS2. Cells were grown in galactose or grown in galactose and shifted to glucose for 16 h. Nucleotides with increased or decreased modification in the absence of L19 are indicated by red and blue circles, respectively. RNA extracted from cells treated with DMSO instead of NAI was used as a control. Increasing amounts of primer extension product from cells shifted to glucose were loaded in lanes 6–8 and 10–12 to achieve loading similar to the galactose lanes (5 and 9). (B and C) Nucleotides modified by NAI are indicated on the secondary (B) and tertiary (C) structures of 5.8S rRNA. (D) The PET exit r-proteins L25, L26, L35, and L37 are clustered on top of the modified nucleotides.