INTRACELLULAR ANALYSIS OF IN-VITRO MODIFIED HIV TAT PROTEIN

Human immunodeficiency viruses HIV-1 and HIV-2 encode a Tat protein th at specifically activates transcription from the viral long terminal r epeat. To characterize the properties of the Tat proteins, we have exp ressed them in Escherichia coil. The purified Tat protein was biochemi cally analyzed and tested for activity upon electroporation into human cell lines. This protein electroporation was used for the intracellul ar analysis of in vitro modified Tat protein. Our results indicate tha t the transcriptionally active form of the Tat protein is a monomer. F urthermore, we found that Tat activity is dramatically inhibited by pr eincubation of the protein with strongly reducing agents. In contrast, no inhibitory effect was measured upon incubation with metal-chelatin g reagents. These results suggest that the cysteine residues of Tat ar e involved in the formation of intramolecular disulfide bonds.