Abstract
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 promoter targets. Activation of heterologous targets is speculated to be an integral part of virus-induced pathogenesis. To verify this hypothesis, stable Tat-producing human rhabdomyosarcoma (RD) cell lines were generated. These cell lines produced significant levels of functional 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 proteins along with the appearance of a new 74-kD protein in tal+ 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 greater abundance. Interestingly, a 26-kD protein that was originally present in the G418+/tat− (control) sample disappeared in the presence of Tat. These data support a possible modulator role for Tat in cellular gene expression.
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