Nature: A team from the Institute of Microbiology of the Chinese Academy of Sciences explained in detail the regulation mechanism of arenavirus replication

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)
.

Among them, all arenaviruses known to cause human diseases belong to the genus Mammarenavirus, and their typical representative is Lassa virus (LASV)
.

LASV is mainly prevalent in African countries and can cause 30,000-50,000 infections and about 5,000 deaths every year
.

At present, there are no specific drugs and vaccines for most arenavirus infections, and the treatment of related diseases still has great difficulties
.

 Since the replication of arenavirus 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 functional protein
.

Therefore, drugs that target viral polymerases are expected to achieve good specificity
.

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
.

Revealing the working mechanism of the arenavirus L protein and the molecular mechanism of its interaction with the Z protein is essential 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
.

 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
.

In order to systematically study the replication mechanism of arenavirus, researcher Shi Yi’s team analyzed the two representative viruses LASV and Machupo virus (Machupo virus, MACV) polymerase (L protein) in the OW and NW arenavirus groups.
Fine three-dimensional structure
.

Through structural analysis and biochemical experiments, they 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 its replication and transcription.
Regulation of activity
.

These findings 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)
.

 Recently, the team further studied the molecular mechanism of arenavirus matrix protein Z negatively regulating polymerase activity
.

They used cryo-electron microscopy to analyze the complex structure of LASV and MACV L protein and its corresponding matrix protein Z, and the ternary complex structure of LZ binary complex and 3'-vRNA
.

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
.

 　 Figure 1.
The overall structure of LASV/MACV LZ and its vRNA complex (a) The domain division diagram of L protein and Z protein; (b) Cryo-electron microscopy density map of LASV LZ complex; (c) MACV LZ complex (D) MACV-LZ-vRNA complex forms a homodimer; (e) 3'-vRNA binding site structure details; (f) MACV-LZ-vRNA complex in Z protein The detailed map of the binding site Through the analysis of the LZ interaction interface, the researchers 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 the conformational changes of these two catalytic elements in the process of RNA synthesis, so that the polymerase loses its catalytic activity
.

The researchers further used hydrogen-deuterium exchange mass spectrometry experiments to prove this hypothesis
.

 　　In addition, the researchers found 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
.

Because this binding motif is highly conserved, they 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
.

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
.

 Figure 2: Allosteric regulation of Z protein on polymerase (a) The structure of influenza virus polymerase in the pre-catalytic state, in a closed conformation (PDB ID: 6SZV); (b) According to the structure in (a) and the new coronavirus Polymerase and nucleic acid/drug complex structure (PDB ID: 7CTT) predicted LASV L pre-catalytic conformation structure model; (c) the structural details of motif D and E in LASV L structure; (d) motif D in LASV L (red ) And E (yellow) sequence
.

The peptides that can be detected by mass spectrometry are underlined; (e) The effect of Z protein and its mutants on the deuteration rate of LASV L.
This work systematically studied the structural basis of arenavirus matrix protein Z regulating polymerase activity.
It helps to further understand the molecular mechanism of arenavirus replication and its negative regulation mechanism
.

These findings provide important candidate targets for the development of broad-spectrum antiviral drugs against various highly pathogenic arenaviruses
.

Relevant 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.
" Cunji School of Medicine, University of Chinese Academy of Sciences Doctoral student Xu Xin, associate researcher Peng Ruchao of the Institute of Microbiology of the Chinese Academy of Sciences, and assistant researcher Peng Qi are the co-first authors of the paper, and researcher Shi Yi is the corresponding author
.

In addition, experts such as Gao Fu, academician of the Institute of Microbiology of the Chinese Academy of Sciences, researcher Qi Jianxun, and Professor Wang Peiyi, director of the cryo-electron microscopy center of Southern University of Science and Technology, also provided strong support
.

The project has won the key strategic pilot science and technology project of the Chinese Academy of Sciences (Category B), the National Science and Technology Major Project, the National Natural Science Foundation of China Outstanding Youth Fund Project and the Youth Science Fund Project, the Chinese Science and Technology Association Young Talents Entrusted Project and the Chinese Academy of Sciences Funding support for projects such as the Youth Innovation Promotion Association
.

 Link to the paper: https:// Hot Article Selections in 2020 1.
The cup is ready! A full paper cup of hot coffee, full of plastic particles.
.
.
2.
Scientists from the United States, Britain and Australia “Natural Medicine” further prove that the new coronavirus is a natural evolution product, or has two origins.
.
.
3.
NEJM: Intermittent fasting is right The impact of health, aging and disease 4.
Heal insomnia within one year! The study found that: to improve sleep, you may only need a heavy blanket.
5.
New Harvard study: Only 12 minutes of vigorous exercise can bring huge metabolic benefits to health.
6.
The first human intervention experiment: in nature.
"Feeling and rolling" for 28 days is enough to improve immunity.
7.
Junk food is "real rubbish"! It takes away telomere length and makes people grow old faster! 8.
Cell puzzle: you can really die if you don't sleep! But the lethal changes do not occur in the brain, but in the intestines.
.
.
9.
The super large-scale study of "Nature Communications": The level of iron in the blood is the key to health and aging! 10.
Unbelievable! Scientists reversed the "permanent" brain damage in animals overnight, and restored the old brain to a young state.
.
.