Host Cell Protein MCM7 Interacts with NP1 of Minute Virus of Canines and Facilitates Viral DNA Replication

Minute virus of canines (MVC), which is a member of the Bocaparvovirus genus, is a non-enveloped, single-stranded DNA virus that causes respiratory and gastrointestinal disease in canines, as well as causing infertility and fetal death in pregnant dogs. The non-structural small protein NP1 of bocaparvoviruses is a unique feature that distinguishes the bocaparvovirus subfamily from other parvovirus subfamilies. In the life cycle of the MVC, NP1 plays an indispensable role in viral DNA replication and pre-mRNA processing. Currently, there is a paucity of studies reporting the characterization of host cell proteins interacting with NP1 during MVC replication. In this study, we screened and identified host cell proteins interacting with MVC-NP1 through immunoprecipitation (IP) combined with liquid chromatography and tandem mass spectrometry (LC-MS/MS) analysis; MCM7 (Mini-chromosome Maintenance Protein 7) has been identified and confirmed to interact directly with NP1 through its N-terminal domain. Furthermore, functional studies reveal that MCM7 is essential in MVC replication. The knockdown of MCM7 decreased the expression of this MVC protein significantly, as well as suppressing MVC replication by arresting the cell cycle in the G0/G1 phase during infection. Conversely, up-regulating MCM7 can rehabilitate the expression of MVC proteins, as well as supporting MVC replication. In conclusion, this study elucidates the interaction between the NP1 protein of MVC and the host factor MCM7, demonstrating that MCM7 is a key factor in the replication process of MVC. These findings provide a potential target for future antiviral therapy.