Regulation of stringent mitochondrial transcription in yeast following amino-acid deprivation.
In the yeast Saccharomyces cerevisiae, a phenotypically identical stringent response is induced by either nutritional downshift or starvation for a required auxotrophic amino acid (aa); in each case, the response selectively includes transcriptional curtailment for the mitochondrial (mt) genome. We have shown previously that the downshift-induced mt stringent response is governed by changing cellular cyclic AMP (cAMP) levels, via a mt cAMP-dependent protein kinase. In contrast, we demonstrate here that cAMP levels are not altered in yeast following starvation for a required aa, and we use in vitro mt transcription assays with organelles from wild-type and mutant strains to confirm that the aa starvation-induced mt stringent response is not governed by cAMP. Rather, such stringent organellar transcriptional attenuation may result from altered availability of an unidentified small molecule which is probably a product of the cytoplasmic and/or mt protein synthesis systems.
McEntee
C M
CM
Department of Microbiology and Immunology, Medical College of Pennsylvania, Philadelphia 19129.
Cantwell-Ibdah
R
R
Hudson
A P
AP
D000596:Amino Acids / Q000378:metabolism*; D003470:Culture Media; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015536:Down-Regulation / Q000502:physiology; D015966:Gene Expression Regulation, Fungal / Q000502:physiology*; D008928:Mitochondria / Q000378:metabolism*; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000254:growth & development / Q000378:metabolism*; D014158:Transcription, Genetic
D000596:Amino Acids; D003470:Culture Media; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases