Ribosomal protein gene transcription in Saccharomyces cerevisiae shows a biphasic response to nutritional changes.
Nutrients are major determinants of ribosomal protein (rp-) gene transcription in Saccharomyces cerevisiae. In order to investigate the molecular mechanisms underlying this nutritional control, yeast mutants that display defects in the glucose up-shift response of rp-gene transcription were isolated. Interestingly, although growth of these mutants on glucose-containing medium was severely affected an initial increase in rp-gene transcription by nutritional up-shift was still observed. However, at later time points, rp-mRNA levels decreased strongly. Various other types of severe growth limitation also did not prevent the initial up-shift in transcription. The results suggest that the glucose up-shift response of rp-gene transcription comprises two phases: an initial, transient response independent of the actual growth potential, and a sustained response which is dependent on growth and requires both glucose and adequate nitrogen sources. Previously, it was found that protein kinase A (Pka) mediates the initial up-shift response, without the need for regulation of Pka activity by cAMP. The present data substantiate that, besides the RAS/adenylate cyclase pathway, an alternative pathway through Pka regulates rp-gene transcription. In addition, evidence is presented that the sustained response does not require Pka activity. Based on these results, taken together, a model is proposed in which rp-gene transcription is dynamically regulated by multiple signal transduction pathways.
Griffioen
G
G
Department of Biochemistry and Molecular Biology, Vrije Universiteit, The Netherlands.
Laan
R J
RJ
Mager
W H
WH
Planta
R J
RJ
D015152:Blotting, Northern; D003470:Culture Media; D015966:Gene Expression Regulation, Fungal; D005947:Glucose / Q000378:metabolism; D007700:Kinetics; D008954:Models, Biological; D012333:RNA, Messenger / Q000096:biosynthesis; D012269:Ribosomal Proteins / Q000096:biosynthesis*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D013045:Species Specificity; D013997:Time Factors; D014158:Transcription, Genetic
D003470:Culture Media; D012333:RNA, Messenger; D012269:Ribosomal Proteins; D005947:Glucose