Biology subjects

Stonehouse, N. J.

Publications and source records attributed to Stonehouse, N. J..

24 records · Page 2Linked to original sources

bioRxiv2022

Positive strand RNA viruses differ in the constraints they place on the folding of their negative strand

Genome replication of positive strand RNA viruses requires the production of a complementary negative strand RNA that serves as a template for synthesis of more positive strand progeny. Structural RNA elements are important for genome replication, but while they are readily observed in the positive strand, evidence of their existence in the negative strand is more limited. We hypothesised that this was due to viruses differing in their capacity to allow this latter RNA to adopt structural folds. To investigate this, ribozymes were introduced into the negative strand of different viral constructs; the expectation being that if RNA folding occurred, negative strand cleavage and suppression of replication would be seen. Indeed this was what happened with hepatitis C virus (HCV) and feline calicivirus (FCV) constructs. However, little or no impact was observed for chikungunya virus (CHIKV), human rhinovirus (HRV), hepatitis E virus (HEV) and yellow fever virus (YFV) constructs. Reduced cleavage in the negative strand proved to be due to duplex formation with the positive strand. Interestingly, ribozyme-containing RNAs also remained intact when produced in vitro by the HCV polymerase, again due to duplex formation. Overall, our results show that there are important differences in the conformational constraints imposed on the folding of the negative strand between different positive strand RNA viruses.

microbiology↗

bioRxiv2021

Structural insight into Pichia pastoris fatty acid synthase

Type I fatty acid synthases (FASs) are critical metabolic enzymes which are common targets for bioengineering in the production of biofuels and other products. Serendipitously, we identified FAS as a contaminant in a cryoEM dataset of virus-like particles (VLPs) purified from P. pastoris, an important model organism and common expression system used in protein production. From these data, we determined the structure of P. pastoris FAS to 3.1 [A] resolution. While the overall organisation of the complex was typical of type I FASs, we identified several differences in both structural and enzymatic domains through comparison with the prototypical yeast FAS from S. cerevisiae. Using focussed classification, we were also able to resolve and model the mobile acyl-carrier protein (ACP) domain, which is key for function. Ultimately, the structure reported here will be a useful resource for further efforts to engineer yeast FAS for synthesis of alternate products.

microbiology↗

bioRxiv2020

Higher-order structures of the foot-and-mouth disease virus RNA-dependent RNA polymerase required for dynamic inter-molecular interactions involved in viral genome replication

Replication of many positive-sense RNA viruses occurs within intracellular membrane-associated compartments. These are believed to provide a favourable environment for replication to occur, concentrating essential viral structural and non-structural components, as well as protecting these components from host-cell pathogen recognition and innate immune responses. However, the details of the molecular interactions and dynamics within these structures is very limited. One of the key components of the replication machinery is the RNA-dependent RNA polymerase, RdRp. This enzyme has been shown to form higher-order fibrils in vitro. Here, using the RdRp from foot-and-mouth disease virus (termed 3Dpol), we report fibril structures, solved at ~7-9 [A] resolution by cryo-EM, revealing multiple conformations of a flexible assembly. Fitting high-resolution coordinates led to the definition of potential intermolecular interactions. We employed mutagenesis using a sub-genomic replicon system to probe the importance of these interactions for replication. We use these data to propose models for the role of higher order 3Dpol complexes as a dynamic scaffold within which RNA replication can occur.

microbiology↗

bioRxiv2020

The RNA pseudoknots in foot-and-mouth disease virus are dispensable for genome replication but essential for the production of infectious virus.

The positive stranded RNA genomes of picornaviruses comprise a single large open reading frame flanked by 5' and 3' untranslated regions (UTRs). Foot-and-mouth disease virus (FMDV) has an unusually large 5' UTR (1.3 kb) containing five structural domains. These include the internal ribosome entry site (IRES), which facilitates initiation of translation, and the cis-acting replication element (cre). Less well characterised structures are a 5' terminal 360 nucleotide stem-loop, a variable length poly-C-tract of approximately 100-200 nucleotides and a series of two to four tandemly repeated pseudoknots (PKs). We investigated the structures of the PKs by selective 2' hydroxyl acetylation analysed by primer extension (SHAPE) analysis and determined their contribution to genome replication by mutation and deletion experiments. SHAPE and mutation experiments confirmed the importance of the previously predicted PK structures for their function. Deletion experiments showed that although PKs are not essential for replication, they provide genomes with a competitive advantage. However, although replicons and full-length genomes lacking all PKs were replication competent, no infectious virus was rescued from genomes containing less than one PK copy. This is consistent with our earlier report describing the presence of putative packaging signals in the PK region.

molecular biology↗

bioRxiv2019

The Chikungunya virus nsP3 macro domain inhibits activation of the NF-κB pathway

The role of the chikungunya virus (CHIKV) non-structural protein 3 (nsP3) in the virus lifecycle is poorly understood. The protein comprises 3 domains. The N-terminus is a macro domain, biochemically characterised to bind both RNA and ADP-ribose, and to possess ADP-ribosyl hydrolase activity - an enzymatic activity that removes ADP-ribose from mono-ADP-ribosylated proteins. As ADP-ribosylation is important in the signalling pathway leading to activation of the transcription factor NF-{kappa}B, we sought to determine if the macro domain might perturb NF-{kappa}B signalling. We first show that CHIKV infection did not induce NF-{kappa}B activation, and could not block exogenous activation of the pathway via TNF, although TNF treatment did reduce virus titres. Ectopic expression of nsP3 was able to block TNF-mediated NF-{kappa}B activation and this was dependent on the macro domain, as mutations previously shown to disrupt either ADP-ribose binding or hydrolase activity lost the ability to inhibit NF-{kappa}B activation. Lastly, we determined the phenotype of the macro domain mutants in the context of virus infection in a range of cell types. Our data are consistent with cell- and species-dependent roles of the macro domain, however, these phenotypes do not correlate with the ability to inhibit NF-{kappa}B activation suggesting that the macro domain plays multiple independent roles in the virus lifecycle.

microbiology↗

bioRxiv2019

High-Resolution Cryo-EM Reveals Dynamics in the Murine Norovirus Capsid

Rather than acting as rigid symmetrical shells to protect and transmit their genomes, the capsids of non-enveloped, icosahedral viruses co-ordinate multiple, essential processes during the viral life-cycle, and undergo extensive conformational rearrangements to deliver these functions. Capturing conformational flexibility has been challenging, yet could be key in understanding and combating infections that viruses cause. Noroviruses are non-enveloped, icosahedral viruses of global importance to human health. They are a common cause of acute non-bacterial gastroenteritis, yet no vaccines or antiviral agents specific to norovirus are available. Here, we use cryo-electron microscopy to study the high-resolution solution structures of infectious, inactivated and mutant virions of murine norovirus (MNV) as a model for human noroviruses. Together with genetic studies, we show that the viral capsid is highly dynamic. While there is little change to the shell domain of the capsid, the protruding domains that radiate from this are flexible and adopt distinct states both independently and synchronously. In doing so the viral capsid is able to sample a defined range of conformational space, with implications for the maintenance of virion stability and infectivity. These data will aid in developing the first generation of effective control measures against this virus.

microbiology↗