Related Experiment Video

Updated: Jun 30, 2026

Saccharomyces cerevisiae Metabolic Labeling with 4-thiouracil and the Quantification of Newly Synthesized mRNA As a Proxy for RNA Polymerase II Activity
09:21

Saccharomyces cerevisiae Metabolic Labeling with 4-thiouracil and the Quantification of Newly Synthesized mRNA As a Proxy for RNA Polymerase II Activity

Published on: October 22, 2018

Rapamycin induces the G0 program of transcriptional repression in yeast by interfering with the TOR signaling pathway

D Zaragoza1, A Ghavidel, J Heitman

  • 1Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7.

Molecular and Cellular Biology
|July 22, 1998
PubMed

Insights

Rapamycin, an antibiotic, halts cell growth by impacting the TOR pathway. It also represses RNA Polymerase I and III (Pol I and Pol III) transcription, revealing a new role for TOR signaling in nutrient response.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Rapamycin inhibits cellular proliferation by targeting the conserved Target of Rapamycin (TOR) signaling pathway.
  • TOR pathway regulates cell growth and metabolism in response to nutrient availability.
  • Yeast cells treated with rapamycin enter G0 (stationary phase), involving gene expression changes.

Purpose of the Study:

  • To investigate the effect of rapamycin on RNA Polymerase I and III (Pol I and Pol III) gene transcription.
  • To determine if the repression of Pol I and Pol III transcription by rapamycin is dependent on the TOR pathway.
  • To identify the molecular targets of rapamycin-mediated repression of Pol I and Pol III transcription.

Main Methods:

  • Treatment of budding yeast cells with rapamycin.
  • Analysis of gene expression for Pol I, II, and III genes.
  • Biochemical assays using cell extracts, including from a conditional tor2 mutant.
  • Investigation of RNA Pol III and transcription initiation factor TFIIIB activity.

Main Results:

  • Rapamycin treatment leads to transcriptional repression of Pol I and Pol III genes.
  • The down-regulation of Pol III transcription is dependent on the TOR pathway.
  • Transcriptional repression of Pol III is partially translation-independent.
  • RNA Pol III and TFIIIB are identified as targets of rapamycin-mediated repression.

Conclusions:

  • TOR signaling regulates both Pol I and Pol III transcription in response to nutrient growth signals.
  • This regulation involves direct or indirect inhibition of RNA Pol III and TFIIIB.
  • The findings link TOR pathway activity to the control of essential transcription machinery.

More Related Videos

Use of Time-Lapse Microscopy and Stage-Specific Nuclear Depletion of Proteins to Study Meiosis in S. cerevisiae07:48

Use of Time-Lapse Microscopy and Stage-Specific Nuclear Depletion of Proteins to Study Meiosis in S. cerevisiae

Published on: October 11, 2022

Development and Application of Rapamycin-regulated Tyrosine Phosphatases06:56

Development and Application of Rapamycin-regulated Tyrosine Phosphatases

Published on: September 6, 2024

Related Concept Videos

Negative Regulator Molecules01:23

Negative Regulator Molecules

Positive regulators allow a cell to advance through cell cycle checkpoints. Negative regulators have an equally important role as they terminate a cell’s progression through the cell cycle—or pause it—until the cell meets specific criteria.
Eukaryotic Transcription Inhibitors01:52

Eukaryotic Transcription Inhibitors

Certain biochemical processes, such as embryonic development and cell growth regulation, depend on the repression of specific genes. DNA binding proteins known as eukaryotic transcription inhibitors regulate the repression of gene expression in eukaryotes. The presence of these inhibitors at the required location and time in the cell is triggered by the presence of hormones and additional signals from other cells.
Eukaryotic transcription inhibitors usually contain two distinct domains, a DNA...
mTOR Signaling and Cancer Progression03:03

mTOR Signaling and Cancer Progression

The mammalian target of rapamycin or mTOR protein was discovered in 1994 due to its direct interaction with rapamycin. The protein gets its name from a yeast homolog called TOR. The mTOR protein complex in mammalian cells plays a major role in balancing anabolic processes such as the synthesis of proteins, lipids, and nucleotides and catabolic processes, such as autophagy in response to environmental cues, such as availability of nutrients and growth factors.
The mTOR pathway or the...
PI3K/mTOR/AKT Signaling Pathway01:22

PI3K/mTOR/AKT Signaling Pathway

The mammalian target of rapamycin  (mTOR) is a serine/threonine kinase that regulates growth, proliferation, and cell survival in response to hormones, growth factors, or nutrient availability. This kinase exists in two structurally and functionally distinct forms: mTOR complex 1  (mTORC1) and mTOR complex 2  (mTORC2). The first form (mTORC1) is composed of a rapamycin-sensitive Raptor and proline-rich Akt substrate, PRAS40. In contrast,  mTORC2 consists of a rapamycin-insensitive companion...
Repressible Operon: trp Operon01:21

Repressible Operon: trp Operon

The trp operon in Escherichia coli exemplifies a repressible operon. It regulates the synthesis of tryptophan through repressor-mediated transcriptional control and attenuation. This dual regulatory mechanism ensures tryptophan biosynthesis occurs only when needed, conserving cellular resources.Structure of the trp OperonThe trp operon consists of five structural genes (trpE, trpD, trpC, trpB, and trpA) that encode enzymes for tryptophan biosynthesis. These genes are transcribed as a single...
Transcriptional Regulation: Riboswitches01:23

Transcriptional Regulation: Riboswitches

Riboswitches are RNA elements that regulate gene expression by altering their secondary structures in response to specific effector molecules. These elements, located in the leader regions of certain mRNAs, act as transcriptional regulators by toggling between alternative conformations to control downstream gene expression. Riboswitch-mediated regulation is a precise mechanism for modulating biosynthetic pathways, as exemplified by the riboflavin biosynthesis pathway in Bacillus...