Recovery from inhibition of transcription in gamma-irradiated Euglena cells

1. Transcriptional activity was inhibited with low doses of gamma-irradiation which did not cause the death of cells, but induced the delay of cell division in the unicellular alga Euglena. 2. The incorporation of [14C]uracil into cells was inhibited to about 50% of non-irradiated cells immediately after 3 krad irradiation. 3. The suppressed transcriptional activity was gradually recovered after irradiation. At about 12 h post-irradiation, the rate of incorporation of [14C]uracil recovered to that of non-irradiation cells. 4. The synthesis of ribosomal RNA was inhibited immediately after 3 krad irradiation, but it was recovered within 12 h after irradiation. The synthesis of cytosol ribosomal RNA precursor was more strongly inhibited than that of other cytosol ribosomal RNAs. 5. The synthesis of cytoplasmic organelle ribosomal RNA was also inhibited and recovered after 3 krad irradiation.