FIGURE 1 

Correlation between half-life and degree of induction after signal activation for signal transducers and signal inhibitors of five important signal transduction networks. Shown are stimulus-induced expression changes of 134 signalling proteins divided by the standard deviation of all log2-fold change values in the corresponding array data set (z-value; horizontal dimension) in relation to the mRNA and protein half-lives, respectively (vertical dimension). Rapid feedback inhibitors (RFIs), defined as signal inhibitors whose mRNAs are induced (z>1) within 4 h after signal administration (grey box), are generally characterized by mRNAs (squares) and proteins (circles) with very short half-life (<2 h). By contrast, signal transducers (blue) and most long-lived signal inhibitors (red) are not induced within 4 h and have significantly longer half-lives than the RFIs.