Table 2 - uploaded by Martin Högbom
Content may be subject to copyright.
Source publication
Norovirus (NV) is a leading cause of gastroenteritis worldwide and a major public health concern. So far, the replication strategy of NV remains poorly understood, mainly because of the lack of a cell system to cultivate the virus. In this study, the function and the structure of a key viral enzyme of replication, the RNA-dependent RNA polymerase (...
Context in source publication
Similar publications
As the leading cause of acute gastroenteritis worldwide, human noroviruses (HuNoVs) have caused around 685 million cases of infection and nearly $60 billion in losses every year. Despite their highly contagious nature, an effective vaccine for HuNoVs has yet to become commercially available. Therefore, rapid detection and subtyping of noroviruses i...
More than 900 students and teachers at many schools in Jiaxing city developed acute gastroenteritis in February 2014. An immediate epidemiological investigation was conducted to identify the pathogen, infection sources and route of transmission.The probable cases and confirmed cases were defined as students or teachers with diarrhoea or vomiting pr...
Human pathogenic viruses (HPVs) with particular reference to norovirus (NoV) commonly known as ‘the winter vomiting bug’ is the leading causes of viral gastroenteritis worldwide. NoV is present in wastewater in high numbers and coupled with a low infectious dose can endanger public health. Secondary wastewater treatment processes are not designed t...
Human noroviruses (HuNoVs) are the cause of more than 95% of epidemic non-bacterial gastroenteritis worldwide, with some lethal cases. These viral agents affect people of all ages. However, young children and older adults are the highest-risk groups, being affected with the greatest rate of hospitalizations and morbidity cases. HuNoV structural pro...
Background:
Human norovirus is regarded as the leading cause of nonbacterial acute diarrhea in developing and developed countries. Among all genotypes, GII.4 has been the predominant genotype, but in East Asia, it was replaced by the GII.17 in 2014/2015. However, after the prevalence of new GII.17 variant in South China, a sharply increase in the...
Citations
... Previous studies have also suggested that 3D pol (or larger precursors thereof) has an essential cis-acting role in replication (i.e., a structural function which needs to be provided from the replicating genome), which is distinct from a separate trans-acting role (i.e., the enzymatic function of the polymerase that can be supplied by a separate genome) 19,22 . Dimers and higher-order oligomers of RdRp molecules have been reported in a number of positive-sense RNA viruses [23][24][25][26][27] . Furthermore, the 3D pol enzyme of both PV and FMDV has been previously shown to form higher-order fibrillar structures 25,[28][29][30][31] . ...
Replication of many positive-sense RNA viruses occurs within intracellular membrane-associated compartments. These are thought to provide a favourable environment for replication to occur, concentrating essential viral structural and nonstructural 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 3D pol ), we report fibril structures, solved at ~7-9 Å 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 3D pol complexes as a dynamic scaffold within which RNA replication can occur.
... Although the functional relevance of the RdRp dimer remains to be established, we note that RdRp dimerization and oligomerization has been reported for many other viruses including Influenza, Polio, Hepatitis C, Norovirus, and others 33 . RdRp oligomerisation can be important for cooperative template binding 34 and can be critical for the viral life cycle 35,36 . Future work should therefore concentrate on the preparation and functional analysis of the coronavirus RdRp dimer and possible additional higher-order structures of the enzyme. ...
The coronavirus SARS-CoV-2 uses an RNA-dependent RNA polymerase (RdRp) to replicate and transcribe its genome. Previous structures of the RdRp revealed a monomeric enzyme composed of the catalytic subunit nsp12, two copies of subunit nsp8, and one copy of subunit nsp7. Here we report an alternative, dimeric form of the enzyme and resolve its structure at 5.5 Å resolution. In this structure, the two RdRps contain only one copy of nsp8 each and dimerize via their nsp7 subunits to adopt an antiparallel arrangement. We speculate that the RdRp dimer facilitates template switching during production of sub-genomic RNAs. Jochheim et al report an alternative, dimeric form of the coronavirus SARS-CoV-2 RNA dependent RNA polymerase (RdRp), which is used to replicate and transcribe its genome. They resolve its structure at 5.5 Å resolution and speculate that the dimer facilitates template switching during production of sub-genomic RNAs.
... They are: a de novo initiation and primer-independent initiation [82][83][84], back-priming base initiation [79,85,86] and a protein-primed initiation via VPg nucleotidylylation [84,87]. The biochemical features of bacterially expressed recombinant RdRp noroviruses (HuNV and MNV) have been well characterized and in vitro enzymatic activity has been described [87][88][89][90]. Out of these four established mechanisms however, the de novo initiation is the proposed model to be employed by norovirus for the synthesis of both the G RNA and SG RNA by direct interaction between viral RdRp with its' VP1 (at the shell domain). ...
The genomes of positive strand RNA viruses often contain more than one open reading frame. Some of these viruses have evolved novel mechanisms to regulate the synthesis of the other open reading frames that in some cases involved the production of a subgenomic RNA or RNAs. Very often, the presence of the subgenomic RNA is used as indicator for active viral genome replication. Norovirus, a major cause for gastroenteritis as well as with all other caliciviruses follow a typical positive strand RNA viruses genome replication strategy. In addition, noroviruses also produce a subgenomic RNA during their replication in infected cells. Efficient and adequate synthesis of norovirus subgenomic RNA is crucial for successful viral replication and productive infection leading to the generation of infectious viral progeny. This chapter will dissect the significant findings on mechanisms involved in norovirus genome replication as well as focusing on subgenomic RNA production.
... Previous studies have also suggested that 3D pol (or larger precursors thereof) has an essential cis-acting role in replication which is distinct from a separate trans-acting role (Spear et al., 2015;Herod et al., 2016). Dimers and higher-order oligomers of 3D pol molecules have been reported in a number of positive-sense RNA viruses (Hansen et al., 1997;Luo et al., 2000;Lyle et al., 2002;Hogbom et al., 2009;Chinnaswamy et al., 2010;). Furthermore, the 3D pol enzyme of both PV and FMDV has been previously shown to form higher-order fibrillar structures (Lyle et al., 2002, Spagnolo et al., 2010Bentham et al, 2012;Tellez et al., 2011;Wang et al., 2013). ...
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 Å 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.
... The non-structural proteins are associated with the viral replication complex induced membrane clusters, and interaction with host factors to regulate cellular homeostasis and promote viral replication (Hyde et al., 2012;Hyde et al., 2009). NS7 is the viral RNA-dependent RNA polymerase (RdRp) (Högbom et al., 2009;Zamyatkin et al., 2008), responsible for viral replication. ...
Noroviruses are the main causative agents for acute viral gastroenteritis worldwide. RIG-I-like receptors (RLRs) triggered interferon (IFN) activation is essential for host defense against viral infections. In turn, viruses have developed sophisticated strategies to counteract host antiviral response. This study aims to investigate how murine norovirus (MNV) replicase interacts with RLRs-mediated antiviral IFN response. Counterintuitively, we found that the MNV replicase NS7 enhances the activation of poly (I:C)-induced IFN response and the transcription of downstream interferon-stimulated genes (ISGs). Interestingly, NS7 protein augments RIG-I and MDA5-triggered antiviral IFN response, which conceivably involves direct interactions with the caspase activation and recruitment domains (CARDs) of RIG-I and MDA5. Consistently, RIG-I and MDA5 exert anti-MNV activity in human HEK293T cells with ectopic expression of viral receptor CD300lf. This effect requires the activation of JAK/STAT pathway, and is further enhanced by NS7 overexpression. These findings revealed an unconventional role of MNV NS7 as augmenting RLRs-mediated IFN response to inhibit viral replication.
... MNV NS1/2 protein is associated with cell tropism and mediates resistance to interferon-λ (IFN-λ)-mediated clearance used for treating persistent viral infection (10). NS7 is the viral RNA-dependent RNA polymerase (RdRp) that can also modulate innate immune response (11,12). However, the exact interactions of these viral proteins with host innate antiviral immunity remain poorly understood. ...
Noroviruses are the main causative agents of acute viral gastroenteritis, but the host factors that restrict their replication remain poorly identified. Guanylate-binding proteins (GBPs) are IFN-inducible GTPases that exert broad antiviral activity and are important mediators of host defenses against viral infections. Here, we show that both IFN-γ stimulation and murine norovirus (MNV) infection induce GBP2 expression in murine macrophages. Results from loss- and gain-of-function assays indicated that GBP2 is important for IFN-γ–dependent anti-MNV activity in murine macrophages. Ectopic expression of MNV receptor (CD300lf) in human HEK293T epithelial cells conferred susceptibility to MNV infection. Importantly, GBP2 potently inhibited MNV in these human epithelial cells. Results from mechanistic dissection experiments revealed that the N-terminal G domain of GBP2 mediates these anti-MNV effects. R48A and K51A substitutions in GBP2, associated with loss of GBP2 GTPase activity, attenuated the anti-MNV effects of GBP2. Finally, we found that non-structural protein 7 (NS7) of MNV co-localizes with GBP2 and antagonizes the anti-MNV activity of GBP2. These findings reveal that GBP2 is an important mediator of host defenses against murine norovirus.
... Additionally, NIb may interact with other potyviral proteins such as NIa-Pro and VPg [47,48]. The RdRp-RdRp self-interaction seems to be a common feature for positive-sense, single-stranded RNA viruses, including insect-, animal-and human-, and plant-infecting viruses [38,[49][50][51][52][53]. The dimerization or oligomerization of RdRps may increase the stability of these enzymes and protect against degradation. ...
Potyviruses represent the largest group of known plant RNA viruses and include many agriculturally important viruses, such as Plum pox virus, Soybean mosaic virus, Turnip mosaic virus, and Potato virus Y. Potyviruses adopt polyprotein processing as their genome expression strategy. Among the 11 known viral proteins, the nuclear inclusion protein b (NIb) is the RNA-dependent RNA polymerase responsible for viral genome replication. Beyond its principal role as an RNA replicase, NIb has been shown to play key roles in diverse virus–host interactions. NIb recruits several host proteins into the viral replication complexes (VRCs), which are essential for the formation of functional VRCs for virus multiplication, and interacts with the sumoylation pathway proteins to suppress NPR1-mediated immunity response. On the other hand, NIb serves as a target of selective autophagy as well as an elicitor of effector-triggered immunity, resulting in attenuated virus infection. These contrasting roles of NIb provide an excellent example of the complex co-evolutionary arms race between plant hosts and potyviruses. This review highlights the current knowledge about the multifunctional roles of NIb in potyvirus infection, and discusses future research directions.
... Not all proteins encoded by ORF1 have been functionally characterized, but previous studies revealed that the MNV NS1/2 protein associates with the endoplasmic reticulum (ER) and the host protein VAP-A (21,22), whereas NS3 associates with microtubules and lipid-rich bodies in the cytoplasm (23). Further, NS7 acts as the RdRp (24,25), and NS6 is the protease cleaving the polyprotein (26,27). ...
Viruses hijack host machinery and regulate cellular homeostasis to actively replicate their genome, propagate, and cause disease. In retaliation, cells possess various defense mechanisms to detect, destroy, and clear infecting viruses, as well as signal to neighboring cells to inform them of the imminent threat. In this study, we demonstrate that the murine norovirus (MNV) infection stalls host protein translation and the production of antiviral and proinflammatory cytokines. However, virus replication and protein translation still ensue. We show that MNV further prevents the formation of cytoplasmic RNA granules, called stress granules (SGs), by recruiting the key host protein G3BP1 to the MNV replication complex, a recruitment that is crucial to establishing and maintaining virus replication. Thus, MNV promotes immune evasion of the virus by altering protein translation. Together, this evasion strategy delays innate immune responses to MNV infection and accelerates disease onset.
... Norovirus RdRps were shown to form homodimers (Högbom et al., 2009), a phenomenon that had already been described for picornavirus RdRps (Lyle et al., 2002). When different amounts of purified recombinant norovirus RdRp protein were subjected to PAGE in native (non-denaturing) conditions, dimer formation was observed at high protein concentration and subsequently confirmed by a denaturation of the isolated proteins, SDS-PAGE, and Western blotting. ...
... Högbom and coworkers interpret the data as a shift from active monomeric RdRps to more active dimers. They analyzed the cooperativity between RdRp monomers by calculating the Hill coefficient that, in this case, was determined to have a value greater than one, which is indicative of a positive cooperativity (Högbom et al., 2009). ...
The Caliciviridae are viruses with a positive-sense, single-stranded RNA genome that is packaged into an icosahedral, environmentally stable protein capsid. The family contains five genera (Norovirus, Nebovirus, Sapovirus, Lagovirus, and Vesivirus) that infect vertebrates including amphibians, reptiles, birds, and mammals. The RNA-dependent RNA polymerase (RdRp) replicates the genome of RNA viruses and can speed up evolution due to its error-prone nature. Studying calicivirus RdRps in the context of genuine virus replication is often hampered by a lack of suitable model systems. Enteric caliciviruses and RHDV in particular are notoriously difficult to propagate in cell culture; therefore, molecular studies of replication mechanisms are challenging. Nevertheless, research on recombinant proteins has revealed several unexpected characteristics of calicivirus RdRps. For example, the RdRps of RHDV and related lagoviruses possess the ability to expose a hydrophobic motif, to rearrange Golgi membranes, and to copy RNA at unusually high temperatures. This review is focused on the structural dynamics, biochemical properties, kinetics, and putative interaction partners of these RdRps. In addition, we discuss the possible existence of a conserved but as yet undescribed structural element that is shared amongst the RdRps of all caliciviruses.
... Norovirus RdRps were shown to form homodimers (Högbom et al., 2009), a phenomenon that had already been described for picornavirus RdRps (Lyle et al., 2002). When different amounts of purified recombinant norovirus RdRp protein were subjected to PAGE in native (non-denaturing) conditions, dimer formation was observed at high protein concentration and subsequently confirmed by a denaturation of the isolated proteins, SDS-PAGE, and Western blotting. ...
... Högbom and coworkers interpret the data as a shift from active monomeric RdRps to more active dimers. They analyzed the cooperativity between RdRp monomers by calculating the Hill coefficient that, in this case, was determined to have a value greater than one, which is indicative of a positive cooperativity (Högbom et al., 2009). ...
