A PROSPECTIVE VIEW ON PHOSPHATASES AND REPLICATIVE SENESCENCE

Addition of phosphate to proteins by kinases, or its removal by phosph atases, is probably the control mechanism most often used by cells to maintain homeostasis. This mechanism presents the advantage of being f ast, versatile, and easily reversible. It is used by all organisms fro m bacteria to man. Although more is known about the kinases, recent st udies are beginning to shed light on the role of phosphatases, the enz ymes that are responsible for terminating the effects of phosphorylati on. These enzymes are perfect candidates for controlling all the cruci al check points during cell cycle traverse, and as such, will be found to be responsible for many important decision in the life of a cell, including entry into replicative senescence.