INTERACTION BETWEEN THE PROTEIN-KINASE B-RAF AND THE ALPHA-SUBUNIT OFTHE 11S PROTEASOME REGULATOR

Protein kinases of the Raf family act as signal-transducing elements d ownstream of activated cell surface receptors and are involved in the regulation of proliferation, differentiation, and cell survival, where as the role of c-Raf-l as a mitogen-activated protein/extracellular si gnal-regulated kinase activator within the mitogenic cascade is well e stablished, less is known about the mammalian Raf isoforms A-Raf and B -Raf, Here we report that B-Raf binds to PA28 alpha, one of two subuni ts of the 11S regulator of proteasomes, PA28a was isolated as a B-Raf- binding protein in a yeast two-hybrid screen of a PC12 cDNA library, B oth proteins can be coimmunoprecipitated after transient expression in 293 cells, No association could be found between PA28a and A-Raf or c -Raf-l, B-Raf binds to a region in PA28 alpha that is important for it s proteasome-activating function.