Cell cycle independent role of cyclin D3 in host restriction of SARS-CoV-2 infection

The COVID-19 pandemic caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) presents a great threat to human health. The interplay between the virus and host plays a crucial role in successful virus replication and transmission. Understanding host-virus interactions is essential for development of new COVID-19 treatment strategies. Here we show that SARS-CoV-2 infection triggers redistribution of cyclin D1 and cyclin D3 from the nucleus to the cytoplasm, followed by its proteasomal degradation. No changes to other cyclins or cyclin dependent kinases were observed. Further, cyclin D depletion was independent from SARS-CoV-2 mediated cell cycle arrest in early S phase or S/G2/M phase. Cyclin D3 knockdown by small interfering RNA specifically enhanced progeny virus titres in supernatants. Finally, cyclin D3 co-immunoprecipitated with SARS-CoV-2 Envelope and Membrane proteins. We propose that cyclin D3 inhibits virion assembly and is depleted during SARS-CoV-2 infection to restore efficient assembly and release of newly produced virions.