The expression of the major protein kinase C substrate MARCKS (myristoylatedalanine-richCkinase substrate) is controlled by the stability of its mRNA. While the MARCKS mRNA is long living in quiescent fibroblasts (t1/2¼14 h), its half-life time is drastically reduced (t1/2¼2 h) in cells treated with phorbol esters to activate protein kinase C (PKC) or treatedwith growth factors. In a first step to study the underlying mechanism we identified both acis-element on the MARCKS mRNA and the cor-responding trans-acting factors. .
