Progress in arenavirus replication research

Arenaviruses belong to the arenaviridae family (Arenaviridae), which is a class of enveloped, segmented single-stranded negative-stranded RNA virus (Segmented Negative-Sense RNA virus, sNSV)
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Among them, all arenaviruses known to cause human diseases belong to the genus Mammarenavirus, and their typical representative is Lassa virus (LASV)
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LASV is mainly prevalent in African countries, causing a large number of infections and deaths every year
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At present, there are no specific drugs and vaccines for most arenavirus infections, and there are still great difficulties in the treatment of related diseases
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Since the replication of arenaviruses mainly depends on the virus polymerase synthesized by the virus itself, this molecular machine is relatively conserved in all arenaviruses, and the host cell basically does not have the same function of protein
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Therefore, drugs that target viral polymerases are expected to achieve good specificity
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In addition, during the virus life cycle, the arenavirus Z protein can negatively regulate the activity of the polymerase and promote the assembly of virus particles
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Revealing the working mechanism of the arenavirus L protein and the molecular mechanism of its interaction with the Z protein is of great significance for a comprehensive understanding of the replication mechanism of arenavirus, and will also provide new directions for the prevention and treatment of arenavirus infection-related diseases
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According to the evolution of arenavirus and the geographical features of its epidemic, the genus of mammalian arenaviruses can be divided into Old World (OW) and New World (New World, NW) arenavirus groups
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In order to systematically study the replication mechanism of arenavirus, the team of Shi Yi, a researcher at the Institute of Microbiology, Chinese Academy of Sciences, analyzed two representative viruses in the OW and NW arenavirus groups, LASV and Machupo virus (MACV) polymerases ( L protein) fine three-dimensional structure
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Through structural analysis and biochemical experiments, the researchers found that the enzyme activity center of arenavirus polymerase is in a naturally opened active conformation, and revealed the recognition mode of polymerase and RNA, and initially clarified that the polymerase itself dimerizes and replicates.
And regulation of transcriptional activity
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These research results provide key information for understanding the evolutionary connections and differences of different sNSVs, and also provide new candidate targets for subsequent drug design targeting arenavirus polymerase (Nature, 2020, 579: 615-619) )
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Recently, the research team further studied the molecular mechanism of arenavirus matrix protein Z negatively regulating polymerase activity
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The researchers used cryo-electron microscopy to analyze the structure of the complexes of LASV and MACV L proteins and their corresponding matrix protein Z, and the structure of the ternary complexes of the LZ binary complex and 3'-vRNA
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The structure shows that in each pair of complexes, a protein Z is bound to a polymerase as a monomer, and the binding site is located at the periphery of the palm domain (Palm) of the polymerase, which is far away from the RNA binding site, indicating protein Z The binding does not affect the recruitment of RNA templates by the polymerase, suggesting that protein Z may negatively regulate polymerase activity through allosteric effects
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Through the analysis of the LZ interaction interface, the study found that the Z protein binds to the distal end of the two catalytic motifs (motifs D and E) in the polymerase and is located on the adjacent interface of multiple domains.
It is speculated that it may hinder these two The conformational changes of each catalytic element during RNA synthesis, so that the polymerase loses its catalytic activity
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The researchers further used hydrogen-deuterium exchange mass spectrometry experiments to prove this hypothesis
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In addition, the researchers also discovered that the Z protein binds to the L protein through its middle domain, and a highly conserved hydrophobic loop dominates the interaction with the L protein
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Because this binding motif is highly conserved, the researchers also observed that LASV and MACV Z protein and L protein can exhibit cross-inhibitory effects in vitro.
This phenomenon indicates that the OW and NW arenavirus Z protein regulates the conservative mechanism of L protein RNA synthesis
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The above findings provide a new direction for the design of broad-spectrum antiviral drugs targeting polymerases, suggesting that broad-spectrum inhibitors can be developed by inhibiting the conformational changes of the polymerase's conservative functional motifs
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This work system studies the structural basis of arenavirus matrix protein Z regulating polymerase activity, and helps to further understand the molecular mechanism of arenavirus replication and its negative regulation mechanism
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These findings provide important candidate targets for the development of broad-spectrum antiviral drugs against various highly pathogenic arenaviruses
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Relevant research results have been published online in advance as a July cover article in Nature Microbiology, entitled Cryo-EM structures of Lassa and Machupo virus polymerases complexed with cognate regulatory Z proteins identify targets for antivirals
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Xu Xin, a doctoral student at Cunji Medical College of the University of Chinese Academy of Sciences, Peng Ruchao, an associate researcher at the Institute of Microbiology, and Peng Qi, an assistant researcher at the Institute of Microbiology, are the co-first authors of the paper, and Shi Yi is the corresponding author of the paper
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The research work was assisted by Gao Fu, a researcher of the Chinese Academy of Sciences/Institute of Microbiology, Qi Jianxun, a researcher of the Institute of Microbiology, and Wang Peiyi, director/professor of the cryo-electron microscopy center of Southern University of Science and Technology.
Supported by the Excellent Youth Fund Project and Youth Science Fund Project of the National Science Foundation of China, the Young Talents Support Project of the China Association for Science and Technology, and the Youth Innovation Promotion Association of the Chinese Academy of Sciences
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Source: Institute of Microbiology, Chinese Academy of Sciences