title: Dominant and semidominant mutations leading to thermosensitivity of ribonucleic acid biosynthesis in Saccharomyces cerevisiae.
abstract: Different dominant thermosensitive mutations affecting the same gene were selected in Saccharomyces cerevisiae. Ribonucleic acid (RNA) synthesis decreased rapidly and markedly at 37 C in all the mutants whether they were in a homozygous or a heterozygous state. Protein biosynthesis was at first unaffected and then decreased slowly, stopping after 5 h. Measurements of RNA biosynthesis in isolated nuclei as well as in vitro activities of RNA polymerases A and B at 22 and 37 C failed to reveal any difference between mutants and the wild type. Analysis of the nature of the residual RNAs synthesized at the high temperature in the mutants showed a small relative increase in the messenger RNA fraction, but it was not sufficient to indicate a specific inactivation of RNA polymerase A activity. The results suggest an impairment in a common regulatory element for all RNA polymerases acting at the level of the initiation of transcription. Similar mutants with a semidominant phenotype were obtained in which the lesions were in two other unlinked loci.
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology; D002467:Cell Nucleus / Q000378:metabolism; D002474:Cell-Free System; D003513:Cycloheximide / Q000494:pharmacology; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D005656:Fungal Proteins / Q000096:biosynthesis; D005799:Genes, Dominant; D007527:Isoenzymes / Q000378:metabolism; D009154:Mutation; D009566:Nitrates / Q000494:pharmacology; D010619:Phenazines / Q000494:pharmacology; D010641:Phenotype; D011758:Pyrroles / Q000494:pharmacology; D012313:RNA / Q000096:biosynthesis*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000378:metabolism*; D013696:Temperature; D014158:Transcription, Genetic
chemical_list: D000935:Antifungal Agents; D005656:Fungal Proteins; D007527:Isoenzymes; D009566:Nitrates; D010619:Phenazines; D011758:Pyrroles; D012313:RNA; D003513:Cycloheximide; D012321:DNA-Directed RNA Polymerases