scholarly journals Let it go: HIV-1 cis-acting repressive sequences

2021 ◽  
Author(s):  
Philipp Niklas Ostermann ◽  
Anastasia Ritchie ◽  
Johannes Ptok ◽  
Heiner Schaal
Keyword(s):  
Nuclear Export ◽  
Negative Impact ◽  
Cis Acting ◽  
Bioinformatic Tools ◽  
Cellular Genes ◽  
Immunodeficiency Virus ◽  
Underlying Mechanisms ◽  
Predictive Approaches ◽  
Intensive Work ◽  
Hiv 1

After human immunodeficiency virus type 1 (HIV-1) was identified in the early 1980s, intensive work began to understand the molecular basis of HIV-1 gene expression. Subgenomic HIV-1 RNA regions, spread throughout the viral genome, were described to have a negative impact on the nuclear export of some viral transcripts. These studies revealed an intrinsic RNA code as a new form of nuclear export regulation. Since such regulatory regions were later also identified in other viruses as well as in cellular genes, it can be assumed that during evolution, viruses took advantage of them to achieve more sophisticated replication mechanisms. Here, we review HIV-1 cis-acting repressive sequences that have been identified and discuss their possible underlying mechanisms and importance. Additionally, we show how current bioinformatic tools might allow more predictive approaches to identify and investigate them.

scholarly journals Concerted Action of Multiple cis-Acting Sequences Is Required for Rev Dependence of Late Human Immunodeficiency Virus Type 1 Gene Expression

2000 ◽  
Vol 74 (22) ◽  
pp. 10822-10826 ◽  
Author(s):  
Marcus Graf ◽  
Alexandra Bojak ◽  
Ludwig Deml ◽  
Kurt Bieler ◽  
Hans Wolf ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Nuclear Export ◽  
Regulatory Elements ◽  
Cis Acting ◽  
Immunodeficiency Virus ◽  
Responsive Element ◽  
Hiv 1

ABSTRACT Based on the human immunodeficiency virus type 1 (HIV-1)gag gene, subgenomic reporter constructs have been established allowing the contributions of differentcis-acting elements to the Rev dependency of late HIV-1 gene products to be determined. Modification of intragenic regulatory elements achieved by adapting the codon usage of the complete gene to highly expressed mammalian genes resulted in constitutive nuclear export allowing high levels of Gag expression independent from the Rev/Rev-responsive element system and irrespective of the absence or presence of the isolated major splice donor. Leptomycin B inhibitor studies revealed that the RNAs derived from the codon-optimizedgag gene lacking AU-rich inhibitory elements are directed to a distinct, CRM1-independent, nuclear export pathway.

scholarly journals From Capsids to Complexes: Expanding the Role of TRIM5α in the Restriction of Divergent RNA Viruses and Elements

Viruses ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 446
Author(s):  
Kevin M. Rose ◽  
Stephanie J. Spada ◽  
Rebecca Broeckel ◽  
Kristin L. McNally ◽  
Vanessa M. Hirsch ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Molecular Basis ◽  
Human Population ◽  
Rna Viruses ◽  
Arms Race ◽  
Innate Immune ◽  
Immunodeficiency Virus ◽  
Underlying Mechanisms ◽  
Hiv 1

An evolutionary arms race has been ongoing between retroviruses and their primate hosts for millions of years. Within the last century, a zoonotic transmission introduced the Human Immunodeficiency Virus (HIV-1), a retrovirus, to the human population that has claimed the lives of millions of individuals and is still infecting over a million people every year. To counteract retroviruses such as this, primates including humans have evolved an innate immune sensor for the retroviral capsid lattice known as TRIM5α. Although the molecular basis for its ability to restrict retroviruses is debated, it is currently accepted that TRIM5α forms higher-order assemblies around the incoming retroviral capsid that are not only disruptive for the virus lifecycle, but also trigger the activation of an antiviral state. More recently, it was discovered that TRIM5α restriction is broader than previously thought because it restricts not only the human retroelement LINE-1, but also the tick-borne flaviviruses, an emergent group of RNA viruses that have vastly different strategies for replication compared to retroviruses. This review focuses on the underlying mechanisms of TRIM5α-mediated restriction of retroelements and flaviviruses and how they differ from the more widely known ability of TRIM5α to restrict retroviruses.

scholarly journals Localization of HIV-1 RNA in mammalian nuclei.

1996 ◽  
Vol 135 (1) ◽  
pp. 9-18 ◽  
Author(s):  
G Zhang ◽  
M L Zapp ◽  
G Yan ◽  
M R Green
Keyword(s):  
Nuclear Export ◽  
Splice Junction ◽  
Stable Population ◽  
Beta Globin ◽  
Nuclear Retention ◽  
Viral Rnas ◽  
Immunodeficiency Virus ◽  
Nascent Transcripts ◽  
Hiv 1

The Rev protein of human immunodeficiency virus type 1 (HIV-1) facilitates the nuclear export of unspliced and partially spliced viral RNAs. In the absence of Rev, these intron-containing HIV-1 RNAs are retained in the nucleus. The basis for nuclear retention is unclear and is an important aspect of Rev regulation. Here we use in situ hybridization and digital imaging microscopy to examine the intranuclear distributions of intron-containing HIV RNAs and to determine their spatial relationships to intranuclear structures. HeLa cells were transfected with an HIV-1 expression vector, and viral transcripts were localized using oligonucleotide probes specific for the unspliced or spliced forms of a particular viral RNA. In the absence of Rev, the unspliced viral RNAs were predominantly nuclear and had two distinct distributions. First, a population of viral transcripts was distributed as approximately 10-20 intranuclear punctate signals. Actinomycin D chase experiments indicate that these signals represent nascent transcripts. A second, stable population of viral transcripts was dispersed throughout the nucleoplasm excluding nucleoli. Rev promoted the export of this stable population of viral RNAs to the cytoplasm in a time-dependent fashion. Significantly, the distributions of neither the nascent nor the stable populations of viral RNAs coincided with intranuclear speckles in which splicing factors are enriched. Using splice-junction-specific probes, splicing of human beta-globin pre-mRNA occurred cotranscriptionally, whereas splicing of HIV-1 pre-mRNA did not. Taken together, our results indicate that the nucleolus and intranuclear speckles are not involved in Rev regulation, and provide further evidence that efficient splicing signals are critical for cotranscriptional splicing.

scholarly journals C19ORF66 is an Interferon-Stimulated Gene (ISG) which Inhibits Human Immunodeficiency Virus-1

2016 ◽  
Author(s):  
Weidong Xiong ◽  
Deisy Contreras ◽  
Joseph Ignatius Irudayam ◽  
Ayub Ali ◽  
Otto O. Yang ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Nuclear Export ◽  
Splice Variants ◽  
Nuclear Export Signal ◽  
Full Length ◽  
Type I ◽  
Immune Factor ◽  
Immunodeficiency Virus ◽  
P24 Protein ◽  
Hiv 1

ABSTRACTInnate immunity is the first line of defense against invading microbes1. The type I interferon (IFN) pathway plays a key role in controlling Human Immunodeficiency Virus type 1 (HIV-1) replication2,3. We identified an IFN-α stimulated gene C19ORF66 that we term Suppressor of Viral Activity (SVA). Full length SVA-1 protein inhibits HIV-1 by blocking virion production. SVA splice variants truncated at the C-terminus and/or disrupted at the nuclear export signal (NES) lose antiviral activity and localize to nucleus, while full length SVA-1 co-localizes with HIV-1 p24 protein in the cytoplasmic compartment of infected cells. SVA-1 is structurally and functionally conserved across species, including mouse and chimpanzee. We provide the first description of the effector function of the gene SVA/C190RF66 as an innate immune factor with anti-HIV-1 activity.

scholarly journals SRp40 and SRp55 Promote the Translation of Unspliced Human Immunodeficiency Virus Type 1 RNA

2010 ◽  
Vol 84 (13) ◽  
pp. 6748-6759 ◽  
Author(s):  
Chad M. Swanson ◽  
Nathan M. Sherer ◽  
Michael H. Malim
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Nuclear Export ◽  
Sr Proteins ◽  
Rna Recognition Motif ◽  
Genomic Rnas ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Nuclear RNA processing events, such as 5′ cap formation, 3′ polyadenylation, and pre-mRNA splicing, mark mRNA for efficient translation. Splicing enhances translation via the deposition of the exon-junction complex and other multifunctional splicing factors, including SR proteins. All retroviruses synthesize their structural and enzymatic proteins from unspliced genomic RNAs (gRNAs) and must therefore exploit unconventional strategies to ensure their effective expression. Here, we report that specific SR proteins, particularly SRp40 and SRp55, promote human immunodeficiency virus type 1 (HIV-1) Gag translation from unspliced (intron-containing) viral RNA. This activity does not correlate with nucleocytoplasmic shuttling capacity and, in the case of SRp40, is dependent on the second RNA recognition motif and the arginine-serine (RS) domain. While SR proteins enhance Gag expression independent of RNA nuclear export pathway choice, altering the nucleotide sequence of the gag-pol coding region by codon optimization abolishes this effect. We therefore propose that SR proteins couple HIV-1 gRNA biogenesis to translational utilization.

scholarly journals Feline Immunodeficiency Virus Gag Is a Nuclear Shuttling Protein

2012 ◽  
Vol 86 (16) ◽  
pp. 8402-8411 ◽  
Author(s):  
Iris Kemler ◽  
Dyana Saenz ◽  
Eric Poeschla
Keyword(s):  
Feline Immunodeficiency Virus ◽  
Nuclear Export ◽  
Leptomycin B ◽  
Genomic Rnas ◽  
Intracellular Location ◽  
Export Pathway ◽  
Immunodeficiency Virus ◽  
Nuclear Shuttling ◽  
Rna Interaction ◽  
Hiv 1

Lentiviral genomic RNAs are encapsidated by the viral Gag protein during virion assembly. The intracellular location of the initial Gag-RNA interaction is unknown. We previously observed feline immunodeficiency virus (FIV) Gag accumulating at the nuclear envelope during live-cell imaging, which suggested that trafficking of human immunodeficiency virus type 1 (HIV-1) and FIV Gag may differ. Here we analyzed the nucleocytoplasmic transport properties of both Gag proteins. We discovered that inhibition of the CRM1 nuclear export pathway with leptomycin B causes FIV Gag but not HIV-1 Gag to accumulate in the nucleus. Virtually all FIV Gag rapidly became intranuclear when the CRM1 export pathway was blocked, implying that most if not all FIV Gag normally undergoes nuclear cycling. In FIV-infected feline cells, some intranuclear Gag was detected in the steady state without leptomycin B treatment. When expressed individually, the FIV matrix (MA), capsid (CA), and nucleocapsid-p2 (NC-p2) domains were not capable of mediating leptomycin B-sensitive nuclear export of a fluorescent protein. In contrast, CA-NC-p2 did mediate nuclear export, with MA being dispensable. We conclude that HIV-1 and FIV Gag differ strikingly in a key intracellular trafficking property. FIV Gag is a nuclear shuttling protein that utilizes the CRM1 nuclear export pathway, while HIV-1 Gag is excluded from the nucleus. These findings expand the spectrum of lentiviral Gag behaviors and raise the possibility that FIV genome encapsidation may initiate in the nucleus.

scholarly journals Restriction of Human Immunodeficiency Virus Type 1 Rev Function in Murine A9 Cells Involves the Rev C-Terminal Domain

2003 ◽  
Vol 77 (5) ◽  
pp. 3084-3090 ◽  
Author(s):  
Sandra M. P. Marques ◽  
Jean-Luc Veyrune ◽  
Ram R. Shukla ◽  
Ajit Kumar
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Nuclear Export ◽  
Productive Infection ◽  
Cell Leukemia Virus Type ◽  
Terminal Domain ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT The human immunodeficiency virus type 1 (HIV-1) Rev and human T-cell leukemia virus type 1 (HTLV-1) Rex proteins are essential for the expression of viral structural proteins and productive infection. Both contain a nuclear export signal (NES) in their C-terminal domain and a nuclear localization signal (NLS) in their N-terminal domain. The NES and NLS are necessary for shuttling between nucleus and cytoplasm and are therefore indispensable for the transport of unspliced and singly spliced viral transcripts. HIV-1 Rev function is restricted in A9 cells, a murine fibroblast cell line, whereas HTLV-1 Rex is functional in these cells. Immunofluorescence studies with RevGFP fusion protein demonstrate normal import and export of Rev in A9 cells. To ascertain which domains of Rev are necessary for the restriction of Rev function in A9 cells, we studied a chimeric construct in which the NES domain of Rev was exchanged with Rex C-terminal amino acids 79 to 95, the Rev1-79/Rex79-95 chimera, which restored Rev function in A9 cells. In addition, overexpression of a truncated Rev containing the Rev C-terminal domain in the presence of wild-type Rev, led to restoration of Rev function in A9 cells. These results suggest that the C-terminal domain of HIV-1 Rev plays an important role in restricting Rev function in murine cells.

scholarly journals Recruitment of the Crm1 Nuclear Export Factor Is Sufficient To Induce Cytoplasmic Expression of Incompletely Spliced Human Immunodeficiency Virus mRNAs

2002 ◽  
Vol 76 (5) ◽  
pp. 2036-2042 ◽  
Author(s):  
Rui Yi ◽  
Hal P. Bogerd ◽  
Bryan R. Cullen
Keyword(s):  
Human Immunodeficiency Virus ◽  
Nuclear Export ◽  
Rna Binding ◽  
Regulatory Protein ◽  
Binding Domain ◽  
Viral Mrnas ◽  
Rev Response Element ◽  
Cytoplasmic Expression ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Cytoplasmic expression of the incompletely spliced RNA transcripts that encode the late, structural proteins of human immunodeficiency virus type 1 (HIV-1) is dependent on the viral Rev regulatory protein. General agreement exists that Rev acts, at least in part, by recruiting the cellular Crm1 nuclear export factor to HIV-1 transcripts bearing the Rev response element RNA target, and thereby inducing their nuclear egress. However, several groups have argued that Crm1 recruitment may not be sufficient for Rev function. Thus, several additional candidate cofactors for Rev have been proposed, and Rev has also been suggested to also inhibit the nuclear splicing of HIV-1 transcripts and/or to directly enhance their cytoplasmic translation. To examine whether Crm1 recruitment is, instead, sufficient to activate the nuclear export of viral mRNAs, we targeted a leucine-rich Crm1 binding domain, derived from a heterologous protein that normally plays no role in RNA metabolism, to HIV-1 RNAs and showed that this tethered Crm1 binding domain is sufficient to induce the nuclear export and cytoplasmic translation of late HIV-1 mRNA species. More importantly, we show that direct tethering of the Crm1 nuclear export factor to target mRNAs, by fusion to a heterologous RNA binding domain, is in and of itself sufficient to induce the nuclear export and cytoplasmic expression of the unspliced HIV-1 mRNAs that encode the viral Gag proteins.

scholarly journals Expression of Exogenous Sam68, the 68-Kilodalton Src-Associated Protein in Mitosis, Is Able To Alleviate Impaired Rev Function in Astrocytes

2002 ◽  
Vol 76 (9) ◽  
pp. 4526-4535 ◽  
Author(s):  
Jinliang Li ◽  
Ying Liu ◽  
In-Woo Park ◽  
Johnny J. He
Keyword(s):  
Gene Expression ◽  
Nuclear Export ◽  
Molecular Mechanisms ◽  
Subcellular Fractionation ◽  
Dominant Negative ◽  
Double Mutation ◽  
Gene Assay ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) gene expression in astrocytes is restricted, resulting in a brief and limited synthesis of HIV-1 viral structural proteins. Impaired Rev function has been documented in these cells. However, the molecular mechanisms underlying the impaired Rev function are not fully understood. Using the astroglial cell line U87.MG as a model, we report here that HIV-1 gene expression down-regulated expression of Sam68, the 68-kDa Src-associated protein in mitosis, which was constitutively expressed at a lower level in astrocytes. Elevating the endogenous level of Sam68 expression considerably restored HIV-1 Rev function in astrocytes, as determined by a Rev-dependent reporter gene assay. However, elevation of Sam68 expression achieved only a modest increase in HIV-1 production, further supporting the notion that there are multiple cellular restrictions of HIV-1 gene expression in astrocytes. Mutagenesis analysis identified the region between amino acids 321 and 410 of Sam68 as being directly involved in the binding of Sam68 to Rev, while a double mutation in Rev, L78D and E79L, like those in the dominant-negative Rev mutant M10, eliminated Rev binding to Sam68. Moreover, subcellular fractionation and digital fluorescence microscopic imaging revealed that Sam68 expression promoted Rev nuclear export. Taken together, our studies demonstrate that a lower level of constitutive Sam68 expression, followed by further down-regulation by HIV-1 infection, contributes to impaired Rev function in astrocytes, and they suggest that Sam68 may play an important role in Rev nuclear export.

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