FIGURE 4.

Temporal order of cistron elimination from the galETKM mRNA. (A) Northern blot (M-probed) of gal mRNA prepared from GW20 (ams1^ts) cells taken at various times after temperature shift-down. The culture of GW20 cells grown up to A₆₀₀ of 0.6 in Luria broth (LB) at 44°C was transferred to 30°C, and growth was allowed to continue. Aliquots of cells were taken at 0, 5, 10, and 20 min after transfer (lanes 2–5). The temperature of the culture at each time point is indicated. Lane 1 is gal mRNA from GW20 cells grown continuously to A₆₀₀ of 0.6 in LB at 30°C. The arrow indicates the putative 17S rRNA, a precursor of 16S rRNA (Li et al., 1999), which were used here as loading controls. (B) Northern blot (M-probed) of gal mRNA from GW20 cells taken at 0, 2, 3, 4, and 5 min after temperature shift-down from 44 to 30°C. Temperature of the culture at each time point is indicated. (C) Changes in the amount of decay intermediate mRNA species after 5, 10, and 20 min of temperature shift-down. Amounts relative to that of time-zero were graphed; galTKM (dark circle), galKM (gray square), and galM (gray triangle). Temperature changes are indicated by a dotted line. (D) Changes in the amount of primary transcripts after 5, 10, and 20 min of temperature shift-down. Amounts relative to that of time-zero were graphed; galETKM (dark circle) and galM1 (gray square). Temperature changes are indicated by a dotted line. (E) Changes in the amount of decay intermediate mRNA species after 2, 3, 4, and 5 min of temperature shift-down. Amounts relative to that of time-zero were graphed; galTKM (dark circle), galKM (gray square), and galM (gray triangle).