Topoisomerase 3b is dispensable for replication of a positive-sense RNA virus--murine coronavirus

Area of Science:

• Virology
• Molecular Biology
• Genetics

Background:

• A DNA-RNA dual-activity topoisomerase complex, TOP3B-TDRD3, was recently implicated in the replication of positive-sense RNA viruses.
• This complex, particularly TOP3B, was proposed as a potential target for antiviral drug development.

Purpose of the Study:

• To investigate the role of TOP3B in the replication of a mouse coronavirus, MHV.
• To evaluate the hypothesis that TOP3B inactivation can inhibit viral replication.

Main Methods:

• Utilized CRISPR-Cas9 gene editing to create Top3b-knockout (KO) and Tdrd3-KO cell lines.
• Infected these cell lines and Top3B-KO mice with MHV.
• Performed immunostaining to assess the localization of Top3b proteins in infected cells.

Main Results:

• Top3b-KO and Tdrd3-KO cell lines showed variable effects on MHV replication.
• No significant changes in MHV replication were observed in the brains or lungs of Top3B-KO mice.
• Top3b proteins were found in stress granules, not co-localized with MHV replication complexes.

Conclusions:

• Top3b does not appear to have a universal role in promoting positive-sense RNA virus replication.
• Targeting TOP3B for antiviral drug development may require further consideration due to its complex role.