Post-transcriptional regulation of gene expression by the Y-box factor ZONAB and cell survival

Lead Research Organisation: University College London
Department Name: Institute of Ophthalmology

Abstract

Epithelia are continuous layers of cells that delineate our tissues and organs. Individual epithelial cells interact with each other via molecular complexes that mediate adhesion but also function as sensors that transmit information about the environment, such as the presence or absence of neighbouring cells, to the cell interior. Integrity of epithelia is important for our organs to function normally and to protect us from our environment. For example, breaches in epithelial layers such as the skin or in the lining of the intestine can lead to serious infections. Epithelial cells thus need molecular mechanisms that ensure proper responses to environmental and cellular factors that would otherwise lead to cell death and tissue damage. This proposal focuses on such a mechanism that is based on a protein that regulates expression of genes. Genes are part of the genome in the nucleus of cells, and encode the proteins that make up our cells and tissues. Genes are first transcribed into an mRNA, a messenger molecule that carries the information to the cellular machinery that synthesizes the proteins. Expression of genes can thus be regulated at different levels: transcription to mRNA, transport and stability of mRNA, and protein synthesis. Our experiments focus on a new mechanism by which epithelial cells respond to stress conditions to regulate the stability of mRNA and/or protein synthesis. This mechanism is important for cell survival as inactivation results in cell death in response to stress. The main component of this mechanism is a molecule that is regulated by adhesion complexes between cells as well as regulatory pathways known to be important for cellular responses. Our aims are to identity the molecular mechanisms by which this central component binds to mRNA and how this is stimulated by different stress conditions. We also want to determine which cellular components are directly affected as well as the importance of such components for cell survival. Understanding how cells respond to stress and how they ensure survival is important for our understanding of how tissues and organs form and maintain themselves. Many diseases such as infections and cancer as well as environmental toxins cause cellular stress and understanding how cells respond will help us to design new therapies. In some cases, cell death is the goal of a therapy, as it is in the case of chemotherapy to fight cancer. Hence, identifying mechanisms that keep cells alive will also aid the development of approaches to increase the efficiencies of existing therapies by targeting such mechanisms in combination with chemotherapy.

Technical Summary

Maintenance of epithelial integrity is a fundamental process required for normal organ function. Epithelial cells adhere to each other via junctional complexes, enabling them to form cellular barriers that separate different tissues and body compartments. Tight junctions are one of these intercellular junctions and restrict paracellular permeability. Tight junctions also contribute to the regulation of epithelial proliferation and differentiation via different types of signalling mechanisms. This proposal is based on ZONAB/DbpA, a Y-box transcription factor that is regulated by the tight junction protein ZO-1 as well as other upstream signalling pathways such as RalA/Ras. ZONAB functions as a transcription factor in proliferating cells. Our preliminary data now suggest that ZONAB also serves as a central component of a posttranscriptional regulatory mechanism that is important for cell survival and regulates the expression of important cellular regulatory proteins. Our aims thus are to determine how ZONAB interacts with specific mRNAs, how ZONAB becomes activated in response to specific stress conditions and which of its known upstream regulators is involved in activation, and to analyse functionally relevant posttranscriptional ZONAB targets on a genome-wide scale. The expected results will be important for the understanding of how epithelial cells respond to stress and how posttranscriptional regulation of gene expression contributes to epithelial homeostasis.

Publications

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Terry S (2010) Rho signaling and tight junction functions. in Physiology (Bethesda, Md.)

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Nie M (2012) Stress- and Rho-activated ZO-1-associated nucleic acid binding protein binding to p21 mRNA mediates stabilization, translation, and cell survival. in Proceedings of the National Academy of Sciences of the United States of America

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Balda MS (2014) Tight junctions in health and disease. in Seminars in cell & developmental biology

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Matter K (2014) SnapShot: Epithelial tight junctions. in Cell

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Balda MS (2016) Tight junctions as regulators of tissue remodelling. in Current opinion in cell biology

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Zihni C (2016) Tight junctions: from simple barriers to multifunctional molecular gates. in Nature reviews. Molecular cell biology

 
Description We have discovered a new stress-activated molecular mechanism based on the Y-box factor ZONAB/DbpA that regulates posttranscriptional gene expression and promotes cell survival during stress and proinflammatory signalling in epithelial cells.



1) We discovered a new type of stress-activated molecular mechanism that promotes cell survival by direct binding of its effector molecule, ZONAB, to specific mRNAs, stimulating mRNA stabilisation and increased translational efficiency.



2) We demonstrated that ZONAB activation by stress is mediated by Ras signalling, stimulating activation of the RhoA exchange factor GEF-H1, which in turn stimulates ZONAB. These data indicate that ZONAB represents a new type of Rho effector pathway that mediates posttranscriptonal gene expression.



3) We identified ZONAB mRNA targets that encode proteins crucial for cell survival and behaviour in response to stress. This is exemplified by p21WAF-1/CIP-1, which is upregulated by ZONAB and its depletion has a similar effect on cell survival as ZONAB depletion.
Exploitation Route Cancer treatement to enchance existing drugs As our reseasrch shows that ZONAB is activated by oncogenic Ras and regulates cell survival in response to drugs such as taxol, ZONAB is a potential therapeutic target to potentiate tumour therapy
Sectors Pharmaceuticals and Medical Biotechnology

 
Description The findings are currently employed to design ways to exploit the identified mechanism in deseases affecting epithelial degeneration
First Year Of Impact 2012
Sector Pharmaceuticals and Medical Biotechnology
 
Description Apg-2: At the crossroads of tissue regeneration and degeneration
Amount £100,000 (GBP)
Funding ID R180018A 
Organisation Moorfields Eye Charity 
Sector Charity/Non Profit
Country United Kingdom
Start 09/2018 
End 09/2021
 
Description Pathfinder
Amount £142,000 (GBP)
Organisation Wellcome Trust 
Department Wellcome Trust Bloomsbury Centre
Sector Charity/Non Profit
Country United Kingdom
Start 02/2017 
End 08/2018
 
Description PhD fellowship
Amount £100,000 (GBP)
Organisation Fight for Sight 
Sector Charity/Non Profit
Country United Kingdom
Start 10/2016 
End 09/2019
 
Description PhD fellowship
Amount £100,000 (GBP)
Organisation Fight for Sight 
Sector Charity/Non Profit
Country United Kingdom
Start 10/2012 
End 09/2015
 
Description Research Grant
Amount £84,979 (GBP)
Funding ID ST 15 07 I 
Organisation Moorfields Eye Hospital NHS Foundation Trust 
Department The Special Trustees of Moorfields Eye Hospital General Fund
Sector Charity/Non Profit
Country United Kingdom
Start 04/2016 
End 03/2017
 
Description ZONAB controls endothelial actin cytoskeleton and genes important for angiogenesis and inflammation
Amount £100,000 (GBP)
Funding ID FS/16/23/32071 
Organisation British Heart Foundation (BHF) 
Sector Charity/Non Profit
Country United Kingdom
Start 10/2016 
End 09/2019
 
Title MDCK cell lines 
Description MDCK cells liens expressing inflammatory regulators to study effect interplay between inflammation and epithelial barrier properites 
Type Of Material Cell line 
Provided To Others? No  
Impact Used at talks and is being incorporated into a publication 
 
Title ZONAB controls endothelial actin cytoskeleton and genes important for angiogenesis and inflammation 
Description Endothelial cell junctions have an important role in the function of the endothelium. They provide adhesive contacts between neighbouring cells and provide communication between cells. Proteins at the endothelial junctions are capable of detecting stretch, stress and damage and providing signals to intercellular effector pathways. ZONAB is a ZO-1 associated transcription factor that shuttles from the tight junction to the nucleus in epithelia. Our unpublished results demonstrate that ZONAB contributes to the regulation of endothelial cytoskeletal arrangement, tight junction protein localisation, proliferation, senescence and inflammation. Further characterization of the molecular mechanisms involved in these ZONAB-dependent pathways may therefore highlight novel therapeutic interventions for vascular diseases, such as atherosclerosis. 
Type Of Material Model of mechanisms or symptoms - human 
Year Produced 2016 
Provided To Others? No  
Impact Endothelial cell junctions have an important role in the function of the endothelium. They provide adhesive contacts between neighbouring cells and provide communication between cells. Proteins at the endothelial junctions are capable of detecting stretch, stress and damage and providing signals to intercellular effector pathways. ZONAB is a ZO-1 associated transcription factor that shuttles from the tight junction to the nucleus in epithelia. Our unpublished results demonstrate that ZONAB contributes to the regulation of endothelial cytoskeletal arrangement, tight junction protein localisation, proliferation, senescence and inflammation. Further characterization of the molecular mechanisms involved in these ZONAB-dependent pathways may therefore highlight novel therapeutic interventions for vascular diseases, such as atherosclerosis. 
 
Title ZONAB controls endothelial actin cytoskeleton and genes important for angiogenesis and inflammation > Research Databases & Models Back to top 
Description Cell-base models for testing drugs for endothelial diseases 
Type Of Material Data analysis technique 
Year Produced 2017 
Provided To Others? No  
Impact Endothelial cell junctions have an important role in the function of the endothelium. They provide adhesive contacts between neighbouring cells and provide communication between cells. Proteins at the endothelial junctions are capable of detecting stretch, stress and damage and providing signals to intercellular effector pathways. ZONAB is a ZO-1 associated transcription factor that shuttles from the tight junction to the nucleus in epithelia. Our unpublished results demonstrate that ZONAB contributes to the regulation of endothelial cytoskeletal arrangement, tight junction protein localisation, proliferation, senescence and inflammation. Further characterization of the molecular mechanisms involved in these ZONAB-dependent pathways may therefore highlight novel therapeutic interventions for vascular diseases, such as atherosclerosis. 
 
Description Role of tight junctions in infectious disease 
Organisation University of Zurich
Country Switzerland 
Sector Academic/University 
PI Contribution Analysis of junctional signalling mechanisms in relation of infectious agents
Collaborator Contribution Provision of reagents and information
Impact no outputs yet
Start Year 2015
 
Description ZONAB signalling in inflammation and cell survival, and apical differentiation in the retinal pigment epithelium 
Organisation University College London
Department Institute of Ophthalmology UCL
Country United Kingdom 
Sector Academic/University 
PI Contribution We are performing the analysis with primary cultures in vivo and the collaborators test our in vitro results with mouse experiments
Collaborator Contribution The collaborator performs the in vivo experiments with lentiviral vectors in mouse retinas
Impact A first publication has been published in 2010 (PMID: 21209887) Follow-up work has led to an an extension of this collaboration to apical differentiation in vivo in mouse RPE, which has been funded by the BBSRC
Start Year 2007
 
Description Cardiff-Peking Universities Cancer Institute, invited lecture 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact lively discussions

exchange of information
Year(s) Of Engagement Activity 2013
 
Description Cell Press Tumour Microenvironment LabLinks Symposium 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact diverse audience reached and interesting discussions

new collaboratoin
Year(s) Of Engagement Activity 2012
 
Description Distinguished Lecture UCL Medicine 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact Discussion of future work
Year(s) Of Engagement Activity 2017
 
Description Gordon Research Conference on Signalling by Adhesion Receptors 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Great discussions with peers

established collaborations
Year(s) Of Engagement Activity 2012