Fig 8.

Yeast Las1 is required for the final step of 25S rRNA 5′-end formation. Total RNA extracted from the las1 mutants indicated (see legend to Fig. 7) was analyzed by primer extension performed with oligonucleotide LD1148 (A) or LD915 (B) to analyze pre-rRNA processing in ITS2 or ITS1, respectively. Schematics depict the processing sites and the positions of the oligonucleotides used. The signal observed at position +7 or +8 (C′₁) was quantitated in each lane and normalized to the wild type (A, I).