Rev-T is an avian retrovirus that specifically transforms early lymphoid cells in vivo and in vitro. The oncogene of Rev-T is v- rel; v-rel encodes the transforming protein p59v-rel. v-rel is derived from a normal cellular gene c-rel, and is highly related to the Drosophila dorsal gene. We are interested in the mechanism by which v-rel transforms lymphoid cells, and the reason why it does not transform fibroblast cells. Using linker insertion and in vivo mutagenesis we intend to isolate v-rel mutants that are temperature-sensitive for transformation of lymphoid cells. These mutants will be used in experiments designed to determine if p59v-rel is, or is asssociated with, a protein kinase activity important for its transforming function. If kinase activity does not seem to be important for the v-rel transforming function we will attempt to determine a pertinent biochemical function of p59v-rel using protein purified from bacterial cells expressing the v-rel protein. We will also determine the sites of phosphorylation and the identity of a second nuclear directing function in p59v- rel, and the importance of these sequences for the transforming function using site-directed mutagenesis. The avian protein p59v- rel is toxic in murine fibroblasts. We will determine the v-rel sequences responsible for this toxicity, and whether a non-toxic avian rel protein can transform murine lymphoid cells. If not, we will attempt to isolate a murine c-rel cDNA clone, and by in vitro mutagenesis we will attempt to create a dominant murine rel transforming gene. Using DNA transfer techniques, we will attempt to isolate genes from lymphoid cells that will allow transformation of fibroblast cells. Finally, by making rel-dorsal hybrid genes in retroviral vectors we will determine whether the sequence homology between these two genes also reflects a functional homology between the two proteins. The proposed studies are intended to further our understanding of retroviral transforming processes, and may have relevance to lymphoid tumor development and other normal developmental processes in general.