FIG. 4.

Dhr1p and Dhr2p are required for 18S rRNA synthesis. Total RNA was extracted from MET::dhr1, MET::dhr2, and otherwise isogenic wild-type (W.T.) strains grown in selective minimal medium lacking methionine (0-h time points) and following addition of methionine for the times indicated. RNA was resolved in a 1.2% agarose-formaldehyde gel, transferred to nylon membrane and hybridized with the oligonucleotides indicated. Oligonucleotide (oligo) b does not distinguish between the 33S and 32S pre-rRNAs, while oligonucleotides d and e do not distinguish between the 27SA₂ and 27SA₃ pre-rRNAs. However, the 33S and 27SA₃ pre-rRNAs are very low in abundance and the signals observed are predominantly due to the 32S and 27SA₂ pre-rRNAs.