Cells normally divide in response to signals from their surrounding environment. In the absence of these signals, cells stay in a non-dividing or quiescent state. In contrast to normal cells, cancer cells divide in an autonomous manner and do not need signals from the neighbouring cells. We are studying a protein called E2F4 that plays a key role in maintaining cells in the quiescent state. When cells leave the quiescent state and enter into the cell division cycle, E2F4 is modified by phosphorylation. We will study the mechanisms responsible for phosphorylation of E2F4 and the manner in which phosphorylation affects its function.