VP 1, the major capsid protein of the mouse polyomavirus, binds microtubules, promotes their acetylation and blocks the host cell cycle

VP 1, the major structural protein of the mouse polyomavirus ( MP yV), is the major architectural component of the viral capsid. Its pentamers are able to self‐assemble into capsid‐like particles and to non‐specifically bind DNA . Surface loops of the protein interact with sialic acid of ganglioside receptors. Although the replication cycle of the virus, including virion morphogenesis, proceeds in the cell nucleus, a substantial fraction of the protein is detected in the cytoplasm of late‐phase MP yV‐infected cells. In this work, we detected VP 1 mainly in the cytoplasm of mammalian cells transfected with plasmid expressing VP 1. In the cytoplasm, VP 1‐bound microtubules, including the mitotic spindle, and the interaction of VP 1 with microtubules resulted in cell cycle block at the G2/M phase. Furthermore, in the late phase of MP yV infection and in cells expressing VP 1, microtubules were found to be hyperacetylated. We then sought to understand how VP 1 interacts with microtubules. Dynein is not responsible for the VP 1–microtubule association, as neither overexpression of p53/dynamitin nor treatment with ciliobrevin‐D (an inhibitor of dynein activity) prevented binding of VP 1 to microtubules. A pull‐down assay for VP 1‐interacting proteins identified the heat shock protein 90 (Hsp90) chaperone, and Hsp90 was also detected in the VP 1–microtubule complexes. Although Hsp90 is known to be associated with acetylated microtubules, it does not mediate the interaction between VP 1 and microtubules. Our study provides insight into the role of the major structural protein in MP yV replication, indicating that VP 1 is a multifunctional protein that participates in the regulation of cell cycle progression in MP yV‐infected cells.