Trans-dominant inactivation of HTLV-I and HIV-1 gene expression by mutation of the HTLV-I Rex transactivator

Abstract

The rex gene of the type I human T-cell leukaemia virus (HTLV-I) encodes a phosphorylated nuclear protein of relative molecular mass 27,000 which is required for viral replication. The Rex protein acts by promoting the cytoplasmic expression of the incompletely spliced viral messenger RNAs that encode the virion structural proteins. To identify the biologically important peptide domains within Rex, we introduced a series of mutations throughout its sequence. Two distinct classes of mutations lacking Rex biological activity were identified. One class corresponds to trans-dominant repressors as they inhibit the function of the wild-type Rex protein. The second class of mutants, in contrast, are recessive negative, rather than dominant negative, as they are not appropriately targeted to the cell nucleus. These results indicate the presence of at least two functionally distinct domains within the Rex protein, one involved in protein localization and a second involved in effector function. The trans-dominant Rex mutants may represent a promising new class of anti-viral agents.

Titration of cellular export factors, but not heteromultimerization, is the molecular mechanism of trans-dominant HTLV-1 Rex mutants

“…Overexpression of Rex-GTP resulted in predominant nuclear/nucleolar accumulation (b). Photographs were recorded at di erent parameters to avoid overexposure in (b) The previously reported TD mutant RexWCG13 (Rimsky et al, 1989) or TagRex (Katahira et al, 1995), were less TD than Rexp21-GFP in these transient transfection experiments (data not shown).…”

“…Dominant-negative Rex mutants were de®ned throughout the entire coding sequence of Rex (BoÈ hnlein et al, 1991b;Rimsky et al, 1989;Weichselbraun et al, 1992a). In order to interfere successfully with Rex function and thus, HTLV-1 replication, we investigated the TD potential and the molecular mechanism of TD Rex mutants.…”

Interaction of the human immunodeficiency virus type 1 Rev protein with a structured region in env mRNA is dependent on multimer formation mediated through a basic stretch of amino acids.

“…Moreover, Rex expression can complement a Rev-deficient HIV-1 provirus (Rimsky et al 1988), and mutant Rex proteins, which are transdominant suppressors of Rex function, are also trans-dominant suppressors of Rev function {Rimsky et al 1989). Therefore, it is likely that the same factor(s) required for export of the HIV-1 and HTLV-I structural mRNAs interacts with the Rev and Rex proteins.…”

Distinct domains in herpes simplex virus type 1 US11 protein mediate post-transcriptional transactivation of human T-lymphotropic virus type I envelope glycoprotein gene expression and specific binding to the Rex responsive element.

“…A fragment of the HTLV-I genome (Seiki et al, 1983) located between nucleotides 8601 and 8876 and containing the cDNA encoding the entire XRE was obtained by PCR amplification from pgTAX-LTR (Rimsky et al, 1989) and cloned into pBluescript II KS(j) (pBS, Stratagene). A part of the UL34 gene of HSV-1 (strain KOS) located between the EcoRI and SmaI endonuclease restriction sites of pSG-3 (Goldin et al, 1981) was subcloned into pBS.…”