Our group
The Viral Stress Responses group lead by Prof Nicolas Locker studies the molecular mechanism underpinning how biocondensates or phase-separated organelles contribute to how cells respond and adapt to viruses.
The assembly of membraneless organelles or biocondensates is emerging as a fundamental paradigm for many cellular functions. They form dynamically with liquid-liquid phase separation (LLPS) events generating high local concentrations of RNAs and proteins, separated from the rest of the cell. This spatio-temporal control of biomolecules, including signalling or metabolic enzymes, can impact on RNA metabolism, biochemical reactions and signalling cascades and thus drive adaption to stressful conditions like viral infections. Among biocondensates, stress granules (SGs) can play a central role in health and disease SGs can be either cytoprotective or pro-death, anti-viral or pro-viral. SGs are proposed to act as part of larger coordinated waves of biocondensates assembly in the nucleus – paraspeckles which impact on splicing, and interact with cytoplasmic P-bodies involved in RNA decay.
Over the past years our group has become established as a leader in the field of virology and biocondensates. Our previous work has characterised how calicivirus proteases can specifically target the SG-scaffolding protein G3BP1 for degradation, how norovirus infection repurposes G3BP1 to promote replication and evade stress responses, how the coronavirus IBV regulates SG signalling. We also uncovered novel SG-like cytoplasmic foci induced during viral infection that control viral replication and challenged established dogma by demonstrating SGs store reactive species.
Discovering the guiding principles for how biocondensates are harnessed to direct specialised functions will establish new rules governing host responses to infection, and uncover potential therapeutic targets in the viral life cycle.
Our aims
Our overarching goal is to dissect how biocondensates play a pivotal role in regulating host stress responses and specialise to direct pro- or anti-viral functions.
Using model viruses including flaviviruses (YFV), coronaviruses (IBV), picornaviruses (FMDV), Asfarvirus (ASFV) and others, we will answer the following fundamental questions:
- What are the distinguishing features of virus-induced biocondensates?
- How do biocondensates and their components manipulate host responses to infection and viral replication?
- What is the contribution of mitochondrial stress during infection?
- What are the roles played by biocondensate in vector species such as mosquitoes and ticks?
- How can novel tools be developed to deepen our understanding of biocoendensates and stress responses?
Understanding the role of biocondensates requires a systematic analysis of the principles governing their function during infection, using a combination of high-resolution imaging, biochemical characterisation, mechanistic functional studies, and novel innovative tools to isolate them.
Workstream 1: Characterising the heterogeneity in assembly, dynamics and compositions of virus-induced biocondensates.
We will apply advanced bioimaging and biochemical isolation combined with -omics analysis to establish how different viruses impact biocondensates composition and dynamics. Informed by this compositional analysis we can establish how specific components contribute to different cellular functions and dissecting their impact on biocondensate assembly, antiviral responses, gene expression and viral replication. Given our discovery that biocondensates store reactive species, and unpublished data uncovering a crosstalk between mitochondrial activity and SGs, we will also dissect how virus-induced biocondensates impact on mitochondrial functions and fingerprint stress responses during infection.
Workstream 2: Developing novel pipelines for biocondensate isolation using fluorescence-activated particles sorting (FAPS) and single cell approaches.
Existing methods to isolate biocondensates all have limitations. We are developing particle sorting, combined with fluoresencent probes to isolate virus-induced biocondensates. This will empower the study of biocondensates function in non-engineered animal primary cell systems, or insect cells, an unchartered territory. We will also work with our partners at the University of Surrey to engineer single molecule approaches, allowing to unravel how biocondensates heterogeneity impact on their functions.
Workstream 3: Dissecting the role of biocondensate in vectors.
The impact of biocondensates and phase separation in viral vectors is unknown. We will tackle this gap in knowledge and characterise the regulation of SGs pathways in mosquitoe and tick cells during infection. Given the G3BP1 drosophila homologue Rasputin regulates the translation of several OxPhosph mRNAs, we will also investigate the crosstalk between mitochondrial functions and stress signalling in insect models and its contribution to controlling viral infection. This will open a completely new chapter in biocondensate biology and function.
Our impact
Our work will achieve the following outcomes:
(i) characterise the specialised dynamics and compositions of virus-induced biocondensates;
(ii) uncover specific biocondensates components that regulate antiviral responses and viral replication, revealing their impact during viral infection.
(iii) define how biocondensates communicate during infection and the importance of this for replication. (iv) elucidate the roles of biocondensates in vector species. (v) establish novel tools to characterise biocondensate functions, with applications beyond infections.
This will achieve a giant leap forward in understanding the role of phase separation during viral infection, positioning Pirbright as a leading institute in the emerging field of biocondensates study in infection. This will pave the way to novel discoveries of fundamental virology, but also inform novel therapeutic approaches that target biocondensates.
