APOBEC3G Inhibits Elongation of HIV-1 Reverse Transcripts

APOBEC3G (A3G) is a host cytidine deaminase that, in the absence of Vif, restricts HIV-1 replication and reduces the amount of viral DNA that accumulates in cells. Initial studies determined that A3G induces extensive mutation of nascent HIV-1 cDNA during reverse transcription. It has been proposed that this triggers the degradation of the viral DNA, but there is now mounting evidence that this mechanism may not be correct. Here, we use a natural endogenous reverse transcriptase assay to show that, in cell-free virus particles, A3G is able to inhibit HIV-1 cDNA accumulation not only in the absence of hypermutation but also without the apparent need for any target cell factors. We find that although reverse transcription initiates in the presence of A3G, elongation of the cDNA product is impeded. These data support the model that A3G reduces HIV-1 cDNA levels by inhibiting synthesis rather than by inducing degradation

Lessons from the cat: use of feline immunodeficiency virus (FIV) as a means to develop intervention strategies effective against human immunodeficiency virus type 1 (HIV-1)

In July 1997 the Division of AIDS of the National Institute of Allergy and Infectious Diseases sponsored a workshop entitled "Use of the FTV/Cat Model for Development of Anti-HIV Vaccines and Therapeutics." The purpose of this workshop was to provide a forum for presenting new data arising from FIV research, assess the utility of the FTV/cat model, identify areas applicable to HTV/AIDS research, and solicit input from investigators on scientific gaps that can benefit from additional support.* The meeting brought to the fore numerous areas where the FTV/cat model can serve as a valuable tool for developing new therapeutic strategies and vaccine designs applicable to the treatment and prevention of HIV-1 infection

Lessons from the cat: use of feline immunodeficiency virus (FIV) as a means to develop intervention strategies effective against human immunodeficiency virus type 1 (HIV-1)

In July 1997 the Division of AIDS of the National Institute of Allergy and Infectious Diseases sponsored a workshop entitled "Use of the FTV/Cat Model for Development of Anti-HIV Vaccines and Therapeutics." The purpose of this workshop was to provide a forum for presenting new data arising from FIV research, assess the utility of the FTV/cat model, identify areas applicable to HTV/AIDS research, and solicit input from investigators on scientific gaps that can benefit from additional support.* The meeting brought to the fore numerous areas where the FTV/cat model can serve as a valuable tool for developing new therapeutic strategies and vaccine designs applicable to the treatment and prevention of HIV-1 infection

A mutant tat protein provides strong protection from HIV-1 infection in human CD4+ T cells

Here we show potent inhibition of HIV-1 replication in a human T cell line and primary human CD4+ cells by expressing a single antiviral protein. Nullbasic is a mutant form of the HIV-1 Tat protein that was previously shown to strongly inhibit HIV-1 replication in nonhematopoietic cell lines by targeting three steps of HIV-1 replication: reverse transcription, transport of viral mRNA, and trans-activation of HIV-1 gene expression. Here we investigated gene delivery of Nullbasic, using lentiviral and retroviral vectors. Although Nullbasic could be delivered by lentiviral vectors to target cells, transduction efficiencies were sharply reduced primarily because of negative effects on reverse transcription mediated by Nullbasic. However, Nullbasic did not inhibit transduction of HEK293T cells by a murine leukemia virus (MLV)-based retroviral vector. Therefore, MLV-based virus-like particles were used to transduce and express Nullbasic-EGFP or EGFP in Jurkat cells, a human leukemia T cell line, and Nullbasic-ZsGreen1 or ZsGreen1 in primary human CD4+ cells. HIV-1 replication kinetics were similar in parental Jurkat and Jurkat-EGFP cells, but were strongly attenuated in Jurkat-Nullbasic-EGFP cells. Similarly, virus replication in primary CD4+ cells expressing a Nullbasic-ZsGreen1 fusion protein was inhibited by approximately 8-to 10-fold. These experiments demonstrate the potential of Nullbasic, which has unique inhibitory activity, as an antiviral agent against HIV-1 infection

Crp79p, Like Mex67p, Is an Auxiliary mRNA Export Factor in Schizosaccharomyces pombe

The export of mRNA from the nucleus to the cytoplasm involves interactions of proteins with mRNA and the nuclear pore complex. We isolated Crp79p, a novel mRNA export factor from the same synthetic lethal screen that led to the identification of spMex67p in Schizosaccharomyces pombe. Crp79p is a 710-amino-acid-long protein that contains three RNA recognition motif domains in tandem and a distinct C-terminus. Fused to green fluorescent protein (GFP), Crp79p localizes to the cytoplasm. Like Mex67p, Crp79-GFP binds poly(A)(+) RNA in vivo, shuttles between the nucleus and the cytoplasm, and contains a nuclear export activity at the C-terminus that is Crm1p-independent. All of these properties are essential for Crp79p to promote mRNA export. Crp79p import into the nucleus depends on the Ran system. A domain of spMex67p previously identified as having a nuclear export activity can functionally substitute for the nuclear export activity at the C-terminus of Crp79p. Although both Crp79p and spMex67p function to export mRNA, Crp79p does not substitute for all of spMex67p functions and probably is not a functional homologue of spMex67p. We propose that Crp79p is a nonessential mRNA export carrier in S. pombe