African swine fever virus is the only mammalian infecting virus that encodes type II DNA topoisomerase, which has caused serious harm to the global pig farming industry in recent years. So far, there is still a lack of safe and effective commercial vaccines and drugs. Therefore, research on the encoded type II DNA topoisomerase pP1192R of the virus is beneficial for providing important theoretical basis for the development of anti-African swine fever drugs.

On May 30, 2024, a research group led by Prof. RAO Zihe at the Institute of Biophysics, Chinese Academy of Sciences published a research paper in Nature Communications. This study utilized various experimental techniques, including single-particle cryo-electron microscopy, X-ray crystallography, biochemical experiments, to decipher the conformational dynamics of the full-length type II DNA topoisomerase pP1192R encoded by the African swine fever virus in complex with nucleic acids, and verified its enzymatic activity in vitro.

Firstly, high-resolution structures of three different conformations of the apo state pP1192R protein was obtained, demonstrating different opening directions of the central structural domain of the protein.

Subsequently, the researchers overcame the instability challenge of the N-terminal ATPase domain by adding specific nucleic acid molecules and after sample optimization, successfully capturing the structure of the full-length protein complex bound to linear DNA. The structure showed significant bending of the double-stranded DNA, causing a local transition from the "B-form" configuration to the "A-form".

Furthermore, the researchers directly observed the image of the protein binding plasmid DNA crossover using atomic force microscopy, confirming this binding characteristic.

Finally, through molecular docking, the researchers docked two different types of type II DNA topoisomerase inhibitors as potential starting points for drug design.

This study comprehensively explored the structure and function of the virus-encoded type II DNA topoisomerase through various experimental techniques, revealed the molecular mechanism of the virus type II DNA topoisomerase, provided potential inhibitor design strategies, laid a theoretical foundation for the prevention and control of African swine fever epidemic, and offered potential intervention strategies to mitigate the impact of African swine fever virus.

Fig. The full-length cryo-electron microscopy structure of ASFV pP1192R protein bound to DNA and the crystal structure of the N-terminal ATPase domain

(Image by RAO Zihe's group)

Article link: https://www.nature.com/articles/s41467-024-49047-w

Contact: XIN Yuhui

Institute of Biophysics, Chinese Academy of Sciences

Beijing 100101, China

E-mail: yh2628@mail.ustc.edu.cn

（Reported by Prof. RAO Zihe's group）