Transcription and Degradation of Messenger Ribonucleic Acid for a Glucose Transport System in Neurospora

Cycloheximide prevents derepression of a low Km system (System II) for glucose uptake in Neurospora. Cells previously incubated in sugar-free medium containing cycloheximide subsequently produced System II when transferred to a medium containing repressive concentrations of glucose. The presence of glucose during prior incubation in cycloheximide prevented synthesis of System II during the recovery phase. Synthesis was insensitive to actinomycin D during recovery. Both the rate of synthesis and the amount of System II synthesized increased with the duration (for 40 min) of cycloheximide previous treatment. The capacity of the cell to synthesize System II decreased with a half-life of 50 min during incubation of the cells in cycloheximide and glucose. During translation, the capacity to synthesize System II decayed with a half-life of 8.4 min. The data are consistent with the notion that mRNA specific for System II was synthesized and accumulated during starvation in cycloheximide. Accumulation of mRNA can be explained by the increased half-life of the message observed when translation was blocked by cycloheximide treatment.