Deregulation of the Host Cell Cycle Induced by SARS‐CoV‐2 Nucleocapsid Protein

ABSTRACT

Introduction: The novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARSCoV2) is the causative agent responsible for the COVID-19 pandemic and has resulted in devastating impacts on global public health. The nucleocapsid (N) protein of other coronaviruses, such as SARS-CoV-1, have been previously implicated in the deregulation of the host cell cycle through interactions with cell cycle checkpoint proteins, Cyclin-Dependent Kinases (CDKs) or cyclins. In this study, we highlight the role of SARS-CoV-2 N-protein in modulating CDK expression, thereby, deregulating the host cell cycle. Methods: A549 cells were transfected with pCMV plasmids, harbouring the SARS-CoV-2 N-protein. Protein extracts of control and Nprotein transfected cells were electrophoresed on SDS-PAGE, transferred onto a nitrocellulose membrane and incubated with CDK2 and CDK4 antibodies. The blots were visualized and protein quantification was performed using ImageJ analysis. Results: Transfection of SARS-CoV-2 N resulted in differential expression of CDK2 and CDK4, which are key regulators that drive cell cycle progression through G0 or G1 phase into S phase. Notably, preliminary findings also demonstrate that N protein results in decreased CDK2 and CDK4 expression. Conclusion: The differential expression of CDKs caused by SARS-CoV-2 N-protein suggests its role in inducing cell cycle arrest at the S phase to facilitate SARS-CoV-2 replication. The results from this research may aid in future characterisation of the mechanisms for SARS-CoV-2-mediated cell cycle arrest, and contribute towards the development of novel antiviral strategies and therapies.