Polyoma small T upregulates the expression of cytoskeletal proteins in mammalian cells during mitosis.

Mammalian cells expressing murine polyoma small T antigen are known to undergo prolonged mitotic arrest followed by extensive cell death. However, the detailed mechanism of this process is not fully understood. While studying the mechanism related to small T induced mitotic arrest in mammalian cells, we observed that the expression of various cytoskeletal proteins was unusually altered in polyoma small T expressing cell line. Since most of the cytoskeletal proteins are reoriented during mitosis and are involved in spindle formation, so it was pertinent to investigate the expression of these genes in PyST expressing cell line. In this study, we evaluated the expression of tubulin, vinculin and actin. We report that polyoma small T antigen leads to upregulation of tubulin and vinculin in a time dependent manner with tubulin expression being most significantly affected. Intriguingly, we demonstrate that dividing cells normally change the expression of these proteins during mitotic progression. The alteration in cytoskeletal elements specifically occurs during mitosis as cells arrested in replicative phase did not show any change. Together these results reveal that the protein levels of tubulin and vinculin do not remain constant throughout cell cycle but change during mitosis and in polyoma small T expressing cells.