CHANGES IN CELLULAR PROTEINS ASSOCIATED WITH THE EXPRESSION OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 TRANSACTIVATOR PROTEIN TAT

Earlier studies have revealed a distinct class of regulatory proteins known as trans-activator proteins in diverse biological systems. These proteins have been shown to act on both homologous and heterologous p romoter targets. Activation of heterologous targets is speculated to b e an integral part of virus-induced pathogenesis. To verify this hypot hesis, stable Tat-producing human rhabdomyosarcoma (RD) cell lines wer e generated. These cell lines produced significant levels of functiona l Tat, as measured by transfection with the reporter plasmid pLTR-CAT. Tat-producing cells, although morphologically similar to the control, exhibited a slower growth rate. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of the cellular proteins from control (tat-) and tat+ cells revealed increased quantities of 34- and 40-kD p roteins along with the appearance of a new 74-kD protein in tat+ cells . Subsequent two-dimensional gel analysis revealed several additional differences. Tat+ cell lines produced two proteins of M(r) 19.5 and 44 kD anew, while proteins with M(r) 14.5, 42, and 52.5 kD were in great er abundance. Interestingly, a 26-kD protein that was originally prese nt in the G418+/tat- (control) sample disappeared in the presence of T at. These data support a possible modulator role for Tat in cellular g ene expression.