Figure 1.

A nonstopHIS3 reporter gene cannot complement his3 mutant. (A) Schematic drawing of HIS3 reporter genes used in this study. The shaded boxes indicate open reading frames (ORFs). DNA sequences of the 3′-UTR region are shown and asterisks represent the poly(A) addition sites determined previously (Mahadevan et al, 1997). Translation termination codon of the HIS3 gene is indicated by bold letters, and the first nucleotide that was deleted to construct nonstopHIS3 reporter gene is boxed. (B) W303 cells were transformed with pIT709 (pHIS3-His₆) or pIT711 (phis3-His₆-ns), and transformants were streaked on SC-His plate and incubated for 3 days at 30°C. (C) W303 cells harboring pIT709 (pHIS3-His₆) or pIT711 (phis3-His₆-ns) were grown on SC-Leu medium and total RNAs were prepared. HIS3 or ACT1 mRNAs in strains were detected with Northern blot analysis with DIG-labeled probe. The values under Northern blot show the relative intensity to the amount of wild-type mRNA normalized by control ACT1 mRNA and are shown as the mean values±standard deviations (s.d.), obtained from at least three independent experiments.