INTRACELLULAR SINGLE-CHAIN FV ANTIBODY INHIBITS RAS ACTIVITY IN T-CELL ANTIGEN RECEPTOR-STIMULATED JURKAT CELLS

A mammalian expression vector directing the synthesis of a cytoplasmic single chain Fv version of the Y13-259 anti-Ras antibody was construc ted and co-transfected into the human lymphoid cell line Jurkat togeth er with a reporter construct containing the bacterial gene for chloram phenicol acetyl transferase under the transcriptional control of sever al copies of the binding site for the transcription factor NF-AT. The Ras specific antibody interferes with NF-AT activation upon direct act ivation of the T-cell antigen receptor, whereas activation by direct p rotein kinase C stimulation is less sensitive to the anti-Ras antibody . Furthermore, the observed inhibition is dependent on the ratio of an tibody to reporter plasmid utilized in the transfection experiments.