Endogenous Ty1 transcript and p22 levels from CNC WT and ribosome biogenesis mutants, and BY4742 wild type and a loc1Δ mutant. (A) Northern blot analysis of poly(A)+ RNA hybridized with a 32P-labeled riboprobe containing Ty1 nt 1266–1601. This probe detects Ty1 mRNA, and Ty1 internally initiated (i) RNA that encodes p22/p18. ACT1 served as a loading control. The relative amount of Ty1 transcripts is shown below. (B) Western blot analysis of Ty1 and p22/p18 from total cell extracts using p18 antiserum, which detects Gag isoforms (†), p45, p22, and p18. Pgk1 served as a loading control. The relative amount of p22 and p18 is shown below.