ACUTE-PHASE INDUCED PHOSPHORYLATION OF RAT-LIVER NUCLEOPROTEIN P70 MODULATES ITS BINDING-AFFINITY FOR THE HAPTOGLOBIN GENE

An increase in the binding affinity of rat liver trans-acting nucleopr otein p70 for the hormone responsive element of the rat haptoglobin ge ne in acute-phase reactions has implicated a posttranslational modific ation. This investigation examines the proposed acute-phase related st ructural alterations of p70 using an in vitro phosphorylation/dephosph orylation assay and selective digestion of p70 with Staphylococcal aur eus V8 protease. The results show that p70 requires phosphorylation to express its DNA-binding ability. Selective proteolysis of p70 provide d evidence that acute-phase induced phosphorylation of this protein al ters its conformation in such a way that its DNA-binding ability is in creased.