Real time analysis of gene expression in living yeast cells: Novel approach for accurate cell damage detection

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1 Real time analysis of gene expression in living yeast cells: Novel approach for accurate cell damage detection Amparo Pascual-Ahuir Giner Instituto de Biología Molecular y Celular de Plantas (IBMCP) Universidad Politécnica de Valencia

2 Saccharomyces cerevisiae as a Model Organism STRESS RESPONSE BIOMEDICAL RESEARCH TOXICOLOGY DRUG DISCOVERY BASIC RESEARCH

3 Yeast: A model for understanding cellular stress responses Hyperosmotic Stress -Water efflux Defense Mechanisms -Cell shrinking -Ionicimbalance(Na + ) -Oxidative damage Activation of ion transport Synthesis/accumulationof osmolytes(glycerol) Regulated cell cycle arrest Activation of transcriptional program Modulation of mitochondrial activity

4 The transcriptional program upon osmostress in yeast Hyperosmotic Stress Function mrna mrna Function Transient growth arrest RNA metabolism (Processing, trna synthesis, Splicing) Translation Ribosomal Proteins Others Transcriptional Profiling: Activated genes: 3-4 (23%) Repressedgenes: up to3 Glycerol, trehalose, glycogen metabolism Sugar uptake + metabolism Redox metabolism Mitochondrial functions Antioxidants Chaperones Signal transduction Cell surface proteins Others Osmolyte production Energy supply Protection from oxidative damage Protection from protein denaturation Coordination of stress response

5 Mechanisms of transcriptional control upon osmostress A Sko Transcription off TF Tup Cyc8 Osmostress HOG Transcription on SAGA Tup SWI Cyc8 SNF TF Sch9 Hog RNA Pol II B Transcription off Osmostress Transcription on Hot Msn2,4 TF HOG SAGA Mediator Rpd3 TF Hog RNA Pol II C Transcription on Osmostress Transcription off Rap Ifh Fhl RNA Pol II TOR/PKA Rap Crf Fhl

6 How is gene expression fine tuned during environmental changes? Modes of dynamically modulate transcription at different stress doses STRESS DOSE A B C A B C mrna level C B A min osmostress -How is promoter activity gradually regulated over a range of stress doses? -What are the molecular mechanisms which confer dose dependent promoter activity? -How does cell physiology change the dose sensitive gene expression? We need: A continuous, real time transcription assay in the living cell adaptable to multiple stress doses

7 The use of a real time luciferase assay to monitor promoter dynamics in the living yeast cell Destabilized firefly luciferase (<5min half life in S. cerevisiae) Measurements in small culture aliquots in multiwell setup allow parallel analyses upon many environmental conditions - DOSE-RESPONSE for a given promoter We can obtain a quantitative value the EC5. 2 [%] Rpb3-HA GRE2 mrna GRE2-lucCP+ Rienzo et al., Yeast time[min] GRE2 induction by.3m NaCl

8 Quantitative Analysis of Natural Promoters upon Oxidative Stress GRE2 CTT H 2 O SOD2 time [min] CCP time [min] 25 µm 5 µm µm 2 µm 4 µm 6 µm 8 µm mm 2 mm GRE2 CTT SOD2 CCP time [min] A max SOD2 EC 5 =25µM+/-7µM CTT EC 5 =3µM+/-9µM GRE2 EC 5 =5µM+/-2µM CCP EC 5 =76µM+/-25µM Dose-Response behavior of the GRE2, CTT, SOD2 and CCP promoters SOD2 and CTT activities are especially sensitive to hydrogen peroxide stress H 2 O 2 [µm] Dolz-Edo et al., Mol Cell Biol 23

9 Quantitative Analysis of cis elements upon Oxidative Stress Synthetic Reporter Genes: 3x[TF binding site]-luccp+ 3xCRE 3xSTRE 3xAP Osmostress HOG Sko Stress Msn2,4 Yap Oxidative Stress CRE STRE AP time [min] time [min] time [min] mm 2mM 2.5mM 3mM H 2 O 2 Dolz-Edo et al., Mol Cell Biol 23

10 Dose Response for each element under all stress conditions (NaCl, H 2 O 2, Menadione) Fold Induction Fold Induction Fold Induction AP- CRE STRE H 2 O 2 [µm] Menadione [µm] NaCl [M] Cell physiology modulates the dose response of stress-activated gene expression Dolz-Edo et al., Mol Cell Biol 23

11 Application of quantitative yeast model to study mycotoxins Toxicological study of citrinin. Citrinin triggers an immediate response to oxidative stress characterized by a strong and dose-dependent induction of natural genes. GRE2 3xCRE 3xAP 3xSTRE At present we are using the dose-response assays to study the transcriptional behavior of other stress response promoters (Oxidative, DNA Damage, Mitochondrial dysfunction, cell cycle) Pascual-Ahuir et al., Nutrients 24

12 Current projects: -Generate artificial promoters, with optimized sensitivity and specificity to one particular mycotoxin. DETECT Mycotoxin CURE DEGRADE -Identify the molecular target of toxicity of citrinin. Expand the dose-response assays to study the toxicological effect of Ochratoxin A. -Identify new enzymes for biodegradation.

13 Amparo Pascual-Ahuir Giner (UPV) Markus Proft (CSIC) Alessandro Rienzo Alba Timón Gomez Sara Manzanares Estreder Elena Vanacloig Pedros Daniel Poveda Huertes Carolina Bets Plasencia Sandra Saiz Balbastre Sonia Squeo