To better understand the mechanisms that regulate stable RNA synthesis, we have analyzed the RNA polymerase I and III transcriptional activities of extracts isolated from cells propagated under a variety of conditions. Under balanced growth conditions the levels of both RNA polymerase I- and III-specific transcription increased proportionally with growth rate. Upon nutritional starvation, RNA polymerase I transcription rapidly declined, followed by 5 S rDNA and eventually tDNA transcription. Transcriptional activities in extracts were restored when the nongrowing cultures were resuspended in fresh medium, although growth did not resume. The differential expression of 5 S rDNA and tDNA genes in extracts prepared from cells subjected to partial starvation was traced to a 5 S rDNA-specific inhibitor and not to a defect in any RNA polymerase III transcription factor. Characterization of this inhibitor indicated that it was not 5 S rRNA. It was sensitive to phenol extraction and resistant to RNase, and its target did not appear to be transcription factor IIIA. Not all treatments that slowed or stopped growth down-regulated the stable RNA transcription apparatus. Cells that have been subjected to either energy starvation or cycloheximide treatment still retain the ability to synthesize stable RNA in vitro, suggesting the presence of alternative regulatory mechanisms.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Conditions||Strain||Source||Reference|