p53

It's like one of those old Popeye cartoons.

Popeye and Bluto are fighting. p53 and Mdm2 are fighting.

Popeye and Bluto are fighting for Olive Oyl.

p53 and Mdm2 are fighting for the fate of the cell. It is an epic battle played out daily all over the world, being won and lost every single moment. p53's purpose is to make sure that all of a cell's DNA is properly replicated and not mutated before cell division may proceed. Mdm2 opposes p53 to keep it from clamping down too tightly upon cell division.

Although it may seem that p53 is antagonistic to life by opposing cell division, it is essential for our survival. In multicellular eukaryotic organisms such as we usually are, cell division is tightly regulated. Too little cell division and the organism doesn't work whereas too much cell division results in uncontrolled cell proliferation (also called cancer). So thank your p53. And Mdm2.