Mechanisms of cell transformation induced by polyomavirus

Polyomavirus is a DNA tumor virus that induces a variety of tumors in mice. Its genome encodes three proteins, namely large T (LT), middle T (MT), and small T (ST) antigens, that have been implicated in cell transformation an d tumorigenesis. LT is associated with cell immortalization, whereas MT pla ys an essential role in cell transformation by binding to and activating se veral cytoplasmic proteins that participate in growth factor-induced mitoge nic signal transduction to the nucleus. The use of different MT mutants has led to the identification of MT-binding proteins as well as analysis of th eir importance during cell transformation. Studying the molecular mechanism s of cell transformation by MT has contributed to a better understanding of cell cycle regulation and growth control.