FIG. 4.

Northern blot analysis revealing an increased degradation of CYC1, CYH2, and ACT1 mRNAs that are retained in the nucleus because of the export deficiency caused by nup116-Δ mutation. Furthermore, the Northern blot analysis also revealed that the degradation is suppressed by cbc1-Δ at 37°C. The NUP116 (normal), nup116-Δ, and nup116-Δ cbc1-Δ strains were grown at 25°C to the mid-logarithmic phase of growth. Subsequently, one-half of each culture was transferred to the restrictive temperature of 37°C. Both the cultures of each strain at 25 and 37°C were further incubated for one additional hour at both temperatures, and transcription was inhibited by the addition of thiolutin (4 μg/ml), as described in Materials and Methods. Cells of each strain from both the temperatures, mock shifted and shifted, were harvested after various times of thiolutin addition; Northern blots were prepared with total RNA; the half-lives of CYC1, CYH2, and ACT1 mRNA were determined as described in Materials and Methods and normalized against 18S rRNA shown at the bottom of the figure. The half-lives are presented beside each panel as well as in Table 3.