Activation of a Diphtheria Toxin A Gene by Expression of Human Immunodeficiency Virus-1 Tat and Rev Proteins in Transfected Cells

Abstract

Expression of a gene encoding the diphtheria toxin A (DT-A) fragment, controlled by tissue specific regulatory elements, has previously been used to kill selected cell populations. Here, we have examined the feasibility of controlling DT-A expression using regulatory systems from the human immunodeficiency virus (HIV-1) genome. Plasmids were constructed which express either DT-A or, as a model system, the luciferase (luc) reporter gene, under control of HIV-1 long terminal repeat (LTR) sequences (–167 to +80). While trans-activation by expression of the viral protein Tat was demonstrated, significant basal expression was observed. To reduce basal expression, cis-acting negative regulatory elements from the env region of the HIV-1 genome were inserted in the 3′ untranslated region of both the luc and DT-A constructs. This dramatically reduced basal expression from the HIV LTR, and now both viral regulatory proteins Tat and Rev were required for maximal trans-activation. Such regulation of DT-A expression might be therapeutically applied to selectively kill HIV-infected cells in acquired immunodeficiency syndrome (AIDS) and AIDS-related complex (ARC).

Overview summary

The HIV-1 genome contains complex regulatory systems that can act to repress and activate heterologous genes. We describe regulation of a DT-A gene by HIV-1 trans-acting proteins Tat and Rev. Due to the potent toxicity of DT-A, this could be an effective strategy to eliminate HIV-1-infected cells.