Craig A. Rosen

The location of cis-acting regulatory sequences in the human T cell lymphotropic virus type III (HTLV-III/LAV) long terminal repeat

The location of cis-acting regulatory sequences within the long terminal repeat (LTR) of the human T cell lymphotropic virus type III (HTLV-III/LAV) was determined. An enhancer element capable of increasing the rate of transcription from a heterologous promoter, irrespective of distance and orientation, is located between nucleotides -137 and -17 (cap site +1). The promoter sequences present near the TATA box respond to heterologous enhancers. The sequences present between nucleotides -17 and +80 are responsive to HTLV-III-associated trans-acting regulatory factors. Activation of these sequences by the viral regulatory factors requires the presence of a functional enhancer. The enhancer requirement is nonspecific, as the enhancer sequences of RSV, HTLV-I, and SV40 can functionally replace the HTLV-III enhancer. These findings define a new type of regulatory element, provide insight into the mechanisms that regulate HTLV-III gene expression, and may help to explain the effects of this virus on infected cells.

The trans-activator gene of the human T cell lymphotropic virus type III is required for replication

The trans-activator gene (tat-III) of the human T lymphotropic virus type III (HTLV-III/LAV) is shown to regulate positively the expression of viral proteins. Viruses in which the tat-III gene is deleted are incapable of prolific replication and do not demonstrate cytopathic effects in T4+ cell lines. These defects can be fully complemented in cell lines that constitutively express the tat-III gene product. We conclude that the tat-III gene product is required for efficient replication of HTLV-III in T4+ cells, and for that reason is important for the cytopathic effects of virus infection. These observations predict that inhibitors of the tat-III gene product may constitute effective therapeutic agents.

Disparate effects of two herpesviruses immediate-early gene trans-activators on the HIV-1 LTR

Abstract The BMLF1 region of the Epstein-Barr virus (EBV) genome and the immediate-early (IE) region of human cytomegalovirus (HCMV) both encode proteins which can trans -activate heterologous promoter/chloramphenicol acetyl transferase (CAT) constructs, including a human immunodeficiency virus type-1 promoter/CAT construct. We demonstrate here that this trans -activation by the EBV BMLF1 gene product, which we have previously shown to be largely post-transcriptional, is reporter gene dependent. In contrast, trans -activation by the HCMV-IE gene product(s), previously shown to be mediated at the RNA level, is seen regardless of whether CAT, human growth hormone, or β-galactosidase is used as the reporter gene. Mutational analysis revealed no specific cis -acting sequences within the HIV-1 promoter which were required for trans -activation by the HCMV-IE gene product(s).