Searching across hundreds of databases

Our searching services are busy right now. Your search will reload in five seconds.

Forgot Password

If you have forgotten your password you can enter your email here and get a temporary password sent to your email.

In exponentially growing Saccharomyces cerevisiae cells, rRNA synthesis is determined by the summed RNA polymerase I loading rate rather than by the number of active genes.

Genes encoding rRNA are multicopy and thus could be regulated by changing the number of active genes or by changing the transcription rate per gene. We tested the hypothesis that the number of open genes is limiting rRNA synthesis by using an electron microscopy method that allows direct counting of the number of active genes per nucleolus and the number of polymerases per active gene. Two strains of Saccharomyces cerevisiae were analyzed during exponential growth: a control strain with a typical number of rRNA genes ( approximately 143 in this case) and a strain in which the rRNA gene number was reduced to approximately 42 but which grows as well as controls. In control strains, somewhat more than half of the genes were active and the mean number of polymerases/gene was approximately 50 +/- 20. In the 42-copy strain, all rRNA genes were active with a mean number of 100 +/- 29 polymerases/gene. Thus, an equivalent number of polymerases was active per nucleolus in the two strains, though the number of active genes varied by twofold, showing that overall initiation rate, and not the number of active genes, determines rRNA transcription rate during exponential growth in yeast. Results also allow an estimate of elongation rate of approximately 60 nucleotides/s for yeast Pol I and a reinitiation rate of less than 1 s on the most heavily transcribed genes.

Pubmed ID: 12588976 RIS Download

Mesh terms: Cell Nucleolus | DNA, Ribosomal | Down-Regulation | Gene Deletion | Kinetics | Microscopy, Electron | Models, Genetic | RNA Polymerase I | RNA, Ribosomal | Saccharomyces cerevisiae | Species Specificity | Time Factors | Transcription, Genetic

Research resources used in this publication

None found

Research tools detected in this publication

None found

Data used in this publication

None found

Associated grants

  • Agency: CSR NIH HHS, Id: RG0336
  • Agency: NIGMS NIH HHS, Id: GM35949
  • Agency: NIGMS NIH HHS, Id: GM63952
  • Agency: NIGMS NIH HHS, Id: R01 GM063952
  • Agency: NIGMS NIH HHS, Id: R01 GM035949

Publication data is provided by the National Library of Medicine ® and PubMed ®. Data is retrieved from PubMed ® on a weekly schedule. For terms and conditions see the National Library of Medicine Terms and Conditions.

We have not found any resources mentioned in this publication.