STRUCTURAL AND FUNCTIONAL HOMOLOGY BETWEEN THE 29 KD RAT-LIVER NUCLEOPROTEIN AND THE HIGH-MOBILITY GROUP-1 PROTEIN

A 29 kD soluble rat liver nucleoprotein (p29) has increased binding af finity for the hormone responsive element (RE) of the rat haptoglobin (Hp) gene during the acute-phase reaction. In this work the possibilit y of its structural and functional homology to the high mobility group 1 (HMG1) nonhistone protein constituent of chromatin was examined. Th e results of two-dimensional gel electrophoresis, Southwestern and Wes tern immunoblot analyses, showed that p29 and HMG1 are homologous prot ein species. On the basis of in vitro and in vivo phosphorylation/deph osphorylation experiments, we discuss the modulatory role of phosphate groups in view of the structure and function of p29.