The pag gene product, a physiological inhibitor of c-abl tyrosine kinase, is overexpressed in cells entering S phase and by contact with agents inducing oxidative stress.

The human pag gene product is an inhibitor of the c-abl tyrosine kinase and belongs to a new family of proteins. We show here that higher levels of pag gene expression are observed following induction of proliferation and contact with compounds inducing oxidative stress such as diethyl maleate and sodium arsenate. A weaker overexpression is seen in a macrophage cell line using hydrogen peroxide or menadione as inducers. Pag gene expression increases in synchronized cells entering the S phase. This raises the possibility that elevated levels of pag counteract the cytostatic activity of abl. Treatment of growth arrested cells with diethyl maleate and sodium arsenate induces pag gene overexpression, independently of cell proliferation. Thus, enhanced pag gene expression occurs in two cellular events: proliferation and response to oxidative stress.