Protein degradation regulator as a tumor suppressor.

The removal of unwanted proteins is an important regulator of cell behavior. Some proteins are marked for destruction by being linked to another protein, ubiquitin.  Once they are tagged, proteins are fed into an intracellular 'garbage disposal' called a proteasome.

Cop1 is a protein that helps to tag unwanted proteins with ubiquitin.  Recent research has demonstrated that Cop1 is able to regulate the activity of  the Jun protein, a potent stimulator of cell division.  Cop1 levels were shown to be lower in cancer cells, suggesting that failure of appropriate protein degradation is important in cancer development.