Faculty Opinions recommendation of SV40-encoded microRNAs regulate viral gene expression and reduce susceptibility to cytotoxic T cells.

ABSTRACT Herpesvirus gene expression is divided into immediate-early (IE) or α genes, early (E) or β genes, and late (L) or γ genes on the basis of temporal expression and dependency on other gene products. By using real-time PCR, we have investigated the expression of 35 human herpesvirus 6B (HHV-6B) genes in T cells infected by strain PL-1. Kinetic analysis and dependency on de novo protein synthesis and viral DNA polymerase activity suggest that the HHV-6B genes segregate into six separate kinetic groups. The genes expressed early (groups I and II) and late (groups V and VI) corresponded well with IE and L genes, whereas the intermediate groups III and IV contained E and L genes. Although HHV-6B has characteristics similar to those of other roseoloviruses in its overall gene regulation, we detected three B-variant-specific IE genes. Moreover, genes that were independent of de novo protein synthesis clustered in an area of the viral genome that has the lowest identity to the HHV-6A variant. The organization of IE genes in an area of the genome that differs from that of HHV-6A underscores the distinct differences between HHV-6B and HHV-6A and may provide a basis for further molecular and immunological analyses to elucidate their different biological behaviors.

Download Full-text

The Immune Evasion Paradox: Immunoevasins of Murine Cytomegalovirus Enhance Priming of CD8 T Cells by Preventing Negative Feedback Regulation

Journal of Virology ◽

10.1128/jvi.01510-08 ◽

2008 ◽

Vol 82 (23) ◽

pp. 11637-11650 ◽

Cited By ~ 50

Author(s):

Verena Böhm ◽

Christian O. Simon ◽

Jürgen Podlech ◽

Christof K. Seckert ◽

Dorothea Gendig ◽

...

Keyword(s):

Gene Expression ◽

T Cells ◽

T Cell ◽

Negative Feedback ◽

Cd8 T Cells ◽

Viral Gene Expression ◽

Cd8 T Cell ◽

Murine Cytomegalovirus ◽

Viral Gene ◽

Infected Cells

ABSTRACT Cytomegaloviruses express glycoproteins that interfere with antigen presentation to CD8 T cells. Although the molecular modes of action of these “immunoevasins” differ between cytomegalovirus species, the convergent biological outcome is an inhibition of the recognition of infected cells. In murine cytomegalovirus, m152/gp40 retains peptide-loaded major histocompatibility complex class I molecules in a cis-Golgi compartment, m06/gp48 mediates their vesicular sorting for lysosomal degradation, and m04/gp34, although not an immunoevasin in its own right, appears to assist in the concerted action of all three molecules. Using the Ld-restricted IE1 epitope YPHFMPTNL in the BALB/c mouse model as a paradigm, we provide here an explanation for the paradox that immunoevasins enhance CD8 T-cell priming although they inhibit peptide presentation in infected cells. Adaptive immune responses are initiated in the regional lymph node (RLN) draining the site of pathogen exposure. In particular for antigens that are not virion components, the magnitude of viral gene expression providing the antigens is likely a critical parameter in priming efficacy. We have therefore focused on the events in the RLN and have related priming to intranodal viral gene expression. We show that immunoevasins enhance priming by downmodulating an early CD8 T-cell-mediated “negative feedback” control of the infection in the cortical region of the RLN, thus supporting the model that immunoevasins improve antigen supply for indirect priming by uninfected antigen-presenting cells. As an important consequence, these findings predict that deletion of immunoevasin genes in a replicative vaccine virus is not a favorable option but may, rather, be counterproductive.

Download Full-text

The E3 Ubiquitin-Protein Ligase Cullin 3 Regulates HIV-1 Transcription

Cells ◽

10.3390/cells9092010 ◽

2020 ◽

Vol 9 (9) ◽

pp. 2010 ◽

Cited By ~ 1

Author(s):

Simon Langer ◽

Xin Yin ◽

Arturo Diaz ◽

Alex J. Portillo ◽

David E. Gordon ◽

...

Keyword(s):

Gene Expression ◽

T Cells ◽

Life Cycle ◽

Viral Replication ◽

Viral Gene Expression ◽

Viral Life Cycle ◽

Cellular Proteins ◽

Viral Gene ◽

Cullin 3 ◽

Hiv 1

The infectious life cycle of the human immunodeficiency virus type 1 (HIV-1) is characterized by an ongoing battle between a compendium of cellular proteins that either promote or oppose viral replication. On the one hand, HIV-1 utilizes dependency factors to support and sustain infection and complete the viral life cycle. On the other hand, both inducible and constitutively expressed host factors mediate efficient and functionally diverse antiviral processes that counteract an infection. To shed light into the complex interplay between HIV-1 and cellular proteins, we previously performed a targeted siRNA screen to identify and characterize novel regulators of viral replication and identified Cullin 3 (Cul3) as a previously undescribed factor that negatively regulates HIV-1 replication. Cul3 is a component of E3-ubiquitin ligase complexes that target substrates for ubiquitin-dependent proteasomal degradation. In the present study, we show that Cul3 is expressed in HIV-1 target cells, such as CD4+ T cells, monocytes, and macrophages and depletion of Cul3 using siRNA or CRISPR/Cas9 increases HIV-1 infection in immortalized cells and primary CD4+ T cells. Conversely, overexpression of Cul3 reduces HIV-1 infection in single replication cycle assays. Importantly, the antiviral effect of Cul3 was mapped to the transcriptional stage of the viral life cycle, an effect which is independent of its role in regulating the G1/S cell cycle transition. Using isogenic viruses that only differ in their promotor region, we find that the NF-κB/NFAT transcription factor binding sites in the LTR are essential for Cul3-dependent regulation of viral gene expression. Although Cul3 effectively suppresses viral gene expression, HIV-1 does not appear to antagonize the antiviral function of Cul3 by targeting it for degradation. Taken together, these results indicate that Cul3 is a negative regulator of HIV-1 transcription which governs productive viral replication in infected cells.

Download Full-text

Epigenomic characterization of latent HIV infection identifies latency regulating transcription factors

PLoS Pathogens ◽

10.1371/journal.ppat.1009346 ◽

2021 ◽

Vol 17 (2) ◽

pp. e1009346

Author(s):

Stuart R. Jefferys ◽

Samuel D. Burgos ◽

Jackson J. Peterson ◽

Sara R. Selitsky ◽

Anne-Marie W. Turner ◽

...

Keyword(s):

Gene Expression ◽

T Cells ◽

Transcription Factors ◽

Hiv Infection ◽

Cd4 T Cells ◽

Viral Gene Expression ◽

Viral Gene ◽

Hiv Latency ◽

Latently Infected ◽

Infected Cells

Transcriptional silencing of HIV in CD4 T cells generates a reservoir of latently infected cells that can reseed infection after interruption of therapy. As such, these cells represent the principal barrier to curing HIV infection, but little is known about their characteristics. To further our understanding of the molecular mechanisms of latency, we characterized a primary cell model of HIV latency in which infected cells adopt heterogeneous transcriptional fates. In this model, we observed that latency is a stable, heritable state that is transmitted through cell division. Using Assay of Transposon-Accessible Chromatin sequencing (ATACseq) we found that latently infected cells exhibit greatly reduced proviral accessibility, indicating the presence of chromatin-based structural barriers to viral gene expression. By quantifying the activity of host cell transcription factors, we observe elevated activity of Forkhead and Kruppel-like factor transcription factors (TFs), and reduced activity of AP-1, RUNX and GATA TFs in latently infected cells. Interestingly, latency reversing agents with different mechanisms of action caused distinct patterns of chromatin reopening across the provirus. We observe that binding sites for the chromatin insulator CTCF are highly enriched in the differentially open chromatin of infected CD4 T cells. Furthermore, depletion of CTCF inhibited HIV latency, identifying this factor as playing a key role in the initiation or enforcement of latency. These data indicate that HIV latency develops preferentially in cells with a distinct pattern of TF activity that promotes a closed proviral structure and inhibits viral gene expression. Furthermore, these findings identify CTCF as a novel regulator of HIV latency.

Download Full-text

Tax induces the recruitment of NF-kB to unintegrated HIV-1 DNA to rescue viral gene expression and replication

Journal of Virology ◽

10.1128/jvi.00285-21 ◽

2021 ◽

Author(s):

Ishak D. Irwan ◽

Bryan R. Cullen

Keyword(s):

Gene Expression ◽

T Cells ◽

Viral Gene Expression ◽

Lentiviral Vectors ◽

Expression Vectors ◽

Viral Gene ◽

Epigenetic Marks ◽

Tax Protein ◽

Activation Of Transcription ◽

Hiv 1

We have previously reported that the normally essential step of integration of the HIV-1 proviral DNA intermediate into the host cell genome becomes dispensable in T cells that express the Human T cell leukemia virus 1 (HTLV-1) Tax protein, a known activator of cellular NF-kB. The rescue of integrase (IN) deficient HIV-1 replication by Tax results from the strong activation of transcription from the long terminal repeat (LTR) promoter on episomal HIV-1 DNA, an effect that is closely correlated with the recruitment of activating epigenetic marks, such as H3Ac, and depletion of repressive epigenetic marks, such as H3K9me3, from chromatinized unintegrated proviruses. In addition, activation of transcription from unintegrated HIV-1 DNA coincides with the recruitment of NF-kB to the two NF-kB binding sites found in the HIV-1 LTR enhancer. Here we report that the recruitment of NF-kB to unintegrated viral DNA precedes, and is a prerequisite for, Tax-induced changes in epigenetic marks, so that an IN- HIV-1 mutant lacking both LTR NF-kB sites is entirely non-responsive to Tax and fails to undergo the epigenetic changes listed above. Interestingly, we found that induction of Tax expression at 24 hours post-infection, when unintegrated HIV-1 DNA is already fully repressed by inhibitory chromatin modifications, is able to effectively reverse the epigenetic silencing of that DNA and rescue viral gene expression. Finally, we report that heterologous promoters introduced into IN-deficient HIV-1-based vectors are transcriptionally active even in the absence of Tax and do not increase their activity when the HIV-1 promoter and enhancer, located in the LTR U3 region,are deleted, as has been recently proposed. Importance Integrase-deficient expression vectors based on HIV-1 are becoming increasingly popular as tools for gene therapy in vivo due to their inability to cause insertional mutagenesis. However, many IN- lentiviral vectors are able to achieve only low levels of gene expression and methods to increase this low level have not been extensively explored. Here we analyze how the HTLV-1 Tax protein is able to rescue the replication of IN- HIV-1 in T cells and describe IN- lentiviral vectors, lacking any inserted origin of replication, that are able to express a heterologous gene effectively.

Download Full-text

Primary T-cells from human CD4/CCR5-transgenic rats support all early steps of HIV-1 replication including integration, but display impaired viral gene expression

Retrovirology ◽

10.1186/1742-4690-4-53 ◽

2007 ◽

Vol 4 (1) ◽

pp. 53 ◽

Cited By ~ 16

Author(s):

Christine Goffinet ◽

Nico Michel ◽

Ina Allespach ◽

Hanna-Mari Tervo ◽

Volker Hermann ◽

...

Keyword(s):

Gene Expression ◽

T Cells ◽

Viral Gene Expression ◽

Viral Gene ◽

Transgenic Rats ◽

Hiv 1

Download Full-text

Vpr Stimulates Viral Expression and Induces Cell Killing in Human Immunodeficiency Virus Type 1-Infected Dividing Jurkat T Cells

Journal of Virology ◽

10.1128/jvi.72.6.4686-4693.1998 ◽

1998 ◽

Vol 72 (6) ◽

pp. 4686-4693 ◽

Cited By ~ 125

Author(s):

Xiao-Jian Yao ◽

Andrew J. Mouland ◽

Ramu A. Subbramanian ◽

Janique Forget ◽

Nicole Rougeau ◽

...

Keyword(s):

Gene Expression ◽

Human Immunodeficiency Virus ◽

T Cells ◽

Apoptotic Cell ◽

Biological Activities ◽

Viral Gene Expression ◽

Viral Gene ◽

Jurkat T Cells ◽

Immunodeficiency Virus

ABSTRACT In this study we investigated the effects of Vpr during human immunodeficiency virus (HIV) infection of proliferating Jurkat T cells by using a vesicular stomatitis virus envelope G glycoprotein pseudotyped HIV superinfection system. We observe that the expression of Vpr results in a severe reduction in the life span of HIV type 1 (HIV-1)-infected dividing T cells in culture. In agreement with a recent report (S. A. Stewart, B. Poon, J. B. M. Jowett, and I. S. Chen, J. Virol. 71:5579–5592, 1997), we show that events characteristic of apoptotic cell death are involved in the Vpr-mediated cytopathic effects. Our results also show that infection with viruses expressing the wild-type vprgene results in an increase in viral gene expression and production. Interestingly, the effects of Vpr on cell viability and on viral gene expression both correlate with the ability of the protein to induce a cell cycle arrest in the G2/M phase. Mutagenesis analyses show that the C terminus of Vpr is essential for these biological activities. Although the role of Vpr is currently associated with the infection of nondividing cells, our results suggest that Vpr can also directly increase viral replication in vivo in infected dividing T cells. Furthermore, these in vitro observations suggest that Vpr-mediated cytotoxic effects could contribute to the CD4+ depletion associated with AIDS progression.

Download Full-text