¹The Ruttenberg Cancer Center, Mount Sinai Medical School, One Gustave L Levy Place, Box 1130, New York, New York 10029, USA

²Department of Cell Biology & Anatomy, New York Medical College, Valhalla, New York 10595, USA

^aAuthor for correspondence

Proteasome inhibitors have been used to demonstrate that many proteins of the signal transduction pathways are regulated by degradation via the ubiquitin-proteasome pathway. The key question is what events target specific proteins for ubiquitination at one time and prevent ubiquitination at other times? In this review, we develop the notion that there is a direct relationship between the phosphorylation/dephosphorylation cascade of the signal transduction pathways and the targeting of the regulatory proteins for ubiquitination. We present examples where phosphorylation appears to alter the interaction between the targeting systems and the substrate by modifying the targeting system, the substrate, or both. These interacting systems are seen in the response of p53, c-jun and ATF-2 in cells subjected to stress or DNA damage and to the normal regulated response in a variety of pathways including the IB-NFB and JAK-STAT pathways. The interweaving of the two post-translational networks, phosphorylation and ubiquitination, provides a powerful insight into global regulatory control pathways.

signal transduction; protein stability; stress kinases; regulation of protein ubiquitination; p53; ATF2; c-Jun; NFB; JAK-STAT