<i>Trans</i> -Activator Gene of Human T-Lymphotropic Virus Type III (HTLV-III)

TLDR

Human T‑lymphotropic virus type III encodes a trans‑acting factor that activates genes linked to its long terminal repeat. The study proposes that a second messenger RNA is the transcript of a gene (3′‑orf) located downstream of env. Functional mapping of viral cDNA transcripts localized the major functional domain of this trans‑activator gene to a region immediately upstream of env, previously considered noncoding. The novel trans‑activator gene comprises three exons and produces mRNA via two splicing events linking 5′, middle, and 3′ genomic segments; a truncated splice variant lacking the second exon fails to encode trans‑activating activity, and additional mRNAs were detected for env and gag‑pol genes.

Abstract

Human T-lymphotropic virus type III (HTLV-III) encodes a trans-acting factor that activates the expression of genes linked to the HTLV-III long terminal repeat. By functional mapping of complementary DNA transcripts of viral messenger RNA's the major functional domain of the gene encoding this factor was localized to a region immediately before the env gene of the virus, a region previously thought to be noncoding. This newly identified gene consists of three exons, and its transcription into messenger RNA involves two splicing events bringing together sequences from the 5′ part (287 base pairs), middle (268 base pairs), and 3′ part (1258 base pairs) of the HTLV-III genome. A similar messenger RNA with a truncated second exon (70 base pairs) does not encode a trans -acting function. It is proposed that this second messenger RNA is the transcript of a gene (3′- orf ) located after the env gene. Messenger RNA′s were also identified for the env and gag - pol genes of HTLV-III.