The RNA-Dependent RNA Polymerase NIb of Potyviruses Plays Multifunctional, Contrasting Roles during Viral Infection

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.

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Quercetin and Luteolin Are Single-digit Micromolar Inhibitors of the SARS-CoV-2 RNA-dependent RNA Polymerase

10.21203/rs.3.rs-1149846/v1 ◽

2021 ◽

Author(s):

Federico Munafò ◽

Elisa Donati ◽

Nicoletta Brindani ◽

Giuliano Ottonello ◽

Andrea Armirotti ◽

...

Keyword(s):

Rna Polymerase ◽

Viral Infections ◽

Pharmacological Intervention ◽

Genome Replication ◽

Binding Modes ◽

Rna Dependent Rna Polymerase ◽

Single Digit ◽

Docking Simulations ◽

Starting Point ◽

Viral Genome Replication

Abstract Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly become a global health pandemic. Among the viral proteins, RNA-dependent RNA polymerase (RdRp) is responsible for viral genome replication and has emerged as one of the most promising targets for pharmacological intervention against SARS-CoV-2. To this end, we experimentally tested luteolin and quercetin for their ability to inhibit the RdRp enzyme. These two compounds are ancestors of flavonoid natural compounds known for a variety of basal pharmacological activities. Luteolin and quercetin returned a single-digit IC50 of 4.6 µM and 6.9 µM, respectively. Then, through dynamic docking simulations, we identified possible binding modes of these compounds to a recently published cryo-EM structure of RdRp. Collectively, these data indicate that these two compounds are a valid starting point for further optimization and development of a new class of RdRp inhibitors to treat SARS-CoV-2 and potentially other viral infections.

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A dynamic regulatory interface on SARS-CoV-2 RNA polymerase

10.1101/2020.07.30.229187 ◽

2020 ◽

Cited By ~ 1

Author(s):

Wei Shi ◽

Ming Chen ◽

Yang Yang ◽

Wei Zhou ◽

Shiyun Chen ◽

...

Keyword(s):

Rna Polymerase ◽

Active Center ◽

Antiviral Drug ◽

Polymerase Activity ◽

Genome Replication ◽

Specific Interactions ◽

Global Public Health ◽

Rna Dependent Rna Polymerase ◽

Viral Genome Replication

AbstractThe RNA-dependent RNA polymerase (RdRp) of SARS-CoV-2 is the core machinery responsible for the viral genome replication and transcription and also a major antiviral target. Here we report the cryo-electron microscopy structure of a post-translocated SARS-CoV-2 RdRp core complex, comprising one nsp12, one separate nsp8(I) monomer, one nsp7-nsp8(II) subcomplex and a replicating RNA substrate. Compared with the recently reported SARS-CoV-2 RdRp complexes, the nsp8(I)/nsp7 interface in this RdRp complex shifts away from the nsp12 polymerase. Further functional characterizations suggest that specific interactions between the nsp8(I) and nsp7, together with the rearrangement of nsp8(I)/nsp7 interface, ensure the efficient and processive RNA synthesis by the RdRp complex. Our findings provide a mechanistic insight into how nsp7 and nsp8 cofactors regulate the polymerase activity of nsp12 and suggest a potential new intervention interface, in addition to the canonical polymerase active center, in RdRp for antiviral design.Author summarySince it was first discovered and reported in late 2019, the coronavirus disease 2019 (COVID-19) pandemic caused by highly contagious SARS-CoV-2 virus is wreaking havoc around the world. Currently, no highly effective and specific antiviral drug is available for clinical treatment. Therefore, the threat of COVID-19 transmission necessitates the discovery of more effective antiviral strategies. Viral RNA-dependent RNA polymerase (RdRp) is an important antiviral drug target. Here, our cryo-EM structure of a SARS-CoV-2 RdRp/RNA replicating complex reveals a previously uncharacterized overall shift of the cofactor nsp8(I)/nsp7 interface, leading to its rearrangement. Through in vitro functional test, we found that the specific interactions on the interface are important to the efficient RNA polymerase activity of SARS-CoV-2 RdRp. These observations let us to suggest this interface as a potential new drug intervention site, outside of the canonical polymerase active center, in RdRp for antiviral design. Our findings would provide new insights into regulatory mechanism of this novel SARS-CoV-2 RdRp, contribute to the design of antiviral drugs against SARS-CoV-2, and benefit the global public health.

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