14-3-3 theta binding to cell cycle regulatory factors is enhanced by HIV-1 Vpr

HIV-1 Vpr Functions in Primary CD4+ T Cells

HIV-1 encodes four accesory proteins in addition to its structural and regulatory genes. Uniquely amongst them, Vpr is abundantly present within virions, meaning it is poised to exert various biological effects on the host cell upon delivery. In this way, Vpr contributes towards the establishment of a successful infection, as evidenced by the extent to which HIV-1 depends on this factor to achieve full pathogenicity in vivo. Although HIV infects various cell types in the host organism, CD4+ T cells are preferentially targeted since they are highly permissive towards productive infection, concomitantly bringing about the hallmark immune dysfunction that accompanies HIV-1 spread. The last several decades have seen unprecedented progress in unraveling the activities Vpr possesses in the host cell at the molecular scale, increasingly underscoring the importance of this viral component. Nevertheless, it remains controversial whether some of these advances bear in vivo relevance, since commonly employed cellular models significantly differ from primary T lymphocytes. One prominent example is the "established" ability of Vpr to induce G2 cell cycle arrest, with enigmatic physiological relevance in infected primary T lymphocytes. The objective of this review is to present these discoveries in their biological context to illustrate the mechanisms whereby Vpr supports HIV-1 infection in CD4+ T cells, whilst identifying findings that require validation in physiologically relevant models.

Baculovirus LEF-11 interacts with BmIMPI to induce cell cycle arrest in the G2/M phase for viral replication

Viruses arrest the host cell cycle and using multiple functions of host cells is an important approach for their replication. Baculovirus arrests infected insect cells at both the late S and G2/M phase, but the strategy employed by baculovirus is not clearly understood. Our research suggests that the Bombyx mori nucleopolyhedrovirus (BmNPV) could arrest the cell cycle in the G2/M phase to promote virus replication, and also that the viral protein LEF-11 could inhibit host cell proliferation and arrest the cell cycle by inhibiting the cell cycle checkpoint proteins BmCyclinB and BmCDK1. Furthermore, we found that LEF-11 interacts with BmIMPI to regulate cell proliferation, but not by direct interaction with BmCyclinB or BmCDK1. In addition, our findings showed that BmIMPI was important and necessary for LEF-11 induced cell cycle arrest in the G2/M phase. Moreover, BmIMPI was found to interact with BmCyclinB and BmCDK1, and down-regulate the expression of BmCyclinB and BmCDK1 to compromise the cell cycle and cell proliferation. Taken together, the data presented demonstrated that baculovirus LEF-11 regulates BmIMPI to inhibit host cell proliferation and provide a new insight into the molecular mechanisms employed by viruses to induce cell cycle arrest.

The Multifarious Role of 14-3-3 Family of Proteins in Viral Replication

The 14-3-3 proteins are a family of ubiquitous and exclusively eukaryotic proteins with an astoundingly significant number of binding partners. Their binding alters the activity, stability, localization, and phosphorylation state of a target protein. The association of 14-3-3 proteins with the regulation of a wide range of general and specific signaling pathways suggests their crucial role in health and disease. Recent studies have linked 14-3-3 to several RNA and DNA viruses that may contribute to the pathogenesis and progression of infections. Therefore, comprehensive knowledge of host-virus interactions is vital for understanding the viral life cycle and developing effective therapeutic strategies. Moreover, pharmaceutical research is already moving towards targeting host proteins in the control of virus pathogenesis. As such, targeting the right host protein to interrupt host-virus interactions could be an effective therapeutic strategy. In this review, we generated a 14-3-3 protein interactions roadmap in viruses, using the freely available Virusmentha network, an online virus-virus or virus-host interaction tool. Furthermore, we summarize the role of the 14-3-3 family in RNA and DNA viruses. The participation of 14-3-3 in viral infections underlines its significance as a key regulator for the expression of host and viral proteins.

Proteome Analysis in a Mammalian Cell line Reveals that PLK2 is Involved in Avian Metapneumovirus Type C (aMPV/C)-Induced Apoptosis

Avian metapneumovirus subtype C (aMPV/C) causes an acute respiratory disease that has caused serious economic losses in the Chinese poultry industry. In the present study, we first explored the protein profile in aMPV/C-infected Vero cells using iTRAQ quantitative proteomics. A total of 921 of 7034 proteins were identified as significantly altered by aMPV/C infection. Three selected proteins were confirmed by Western blot analysis. Bioinformatics GO analysis revealed multiple signaling pathways involving cell cycle, endocytosis, and PI3K-Akt, mTOR, MAPK and p53 signaling pathways, which might participate in viral infection. In this analysis, we found that PLK2 expression was upregulated by aMPV/C infection and investigated whether it contributed to aMPV/C-mediated cellular dysfunction. Suppressing PLK2 attenuated aMPV/C-induced reactive oxygen species (ROS) production and p53-dependent apoptosis and reduced virus release. These results in a mammalian cell line suggest that high PLK2 expression correlates with aMPV/C-induced apoptosis and viral replication, providing new insight into the potential avian host cellular response to aMPV/C infection and antiviral targets.

Crosstalk between 14-3-3θ and AF4 enhances MLL-AF4 activity and promotes leukemia cell proliferation

PURPOSE

The t(4;11)(q21;q23) translocation characterizes a form of acute lymphoblastic leukemia with a poor prognosis. It results in a fusion gene encoding a chimeric transcription factor, MLL-AF4, that deregulates gene expression through a variety of still controversial mechanisms. To provide new insights into these mechanisms, we examined the interaction between AF4, the most common MLL fusion partner, and the scaffold protein 14-3-3θ, in the context of t(4;11)-positive leukemia.

METHODS

Protein-protein interactions were analyzed using immunoprecipitation and in vitro binding assays, and by fluorescence microscopy in t(4;11)-positive RS4;11 and MV4-11 leukemia cells and in HEK293 cells. Protein and mRNA expression levels were determined by Western blotting and RT-qPCR, respectively. A 5-bromo-2'-deoxyuridine assay and an annexin V/propidium iodide assay were used to assess proliferation and apoptosis rates, respectively, in t(4;11)-positive and control cells. Chromatin immunoprecipitation was performed to assess binding of 14-3-3θ and AF4 to a specific promoter element.

RESULTS

We found that AF4 and 14-3-3θ are nuclear interactors, that 14-3-3θ binds Ser⁵⁸⁸ of AF4 and that 14-3-3θ forms a complex with MLL-AF4. In addition, we found that in t(4;11)-positive cells, 14-3-3θ knockdown decreased the expression of MLL-AF4 target genes, induced apoptosis and hampered cell proliferation. Moreover, we found that 14-3-3θ knockdown impaired the recruitment of AF4, but not of MLL-AF4, to target chromatin. Overall, our data indicate that the activity of the chimeric transcription factor MLL-AF4 depends on the cellular availability of 14-3-3θ, which triggers the transactivating function and subsequent degradation of AF4.

CONCLUSIONS

From our data we conclude that the scaffold protein 14-3-3θ enhances the aberrant activity of the chimeric transcription factor MLL-AF4 and, therefore, represents a new player in the molecular pathogenesis of t(4;11)-positive leukemia and a new promising therapeutic target.

Breaking Bad: How Viruses Subvert the Cell Cycle

Interactions between the host and viruses during the course of their co-evolution have not only shaped cellular function and the immune system, but also the counter measures employed by viruses. Relatively small genomes and high replication rates allow viruses to accumulate mutations and continuously present the host with new challenges. It is therefore, no surprise that they either escape detection or modulate host physiology, often by redirecting normal cellular pathways to their own advantage. Viruses utilize a diverse array of strategies and molecular targets to subvert host cellular processes, while evading detection. These include cell-cycle regulation, major histocompatibility complex-restricted antigen presentation, intracellular protein transport, apoptosis, cytokine-mediated signaling, and humoral immune responses. Moreover, viruses routinely manipulate the host cell cycle to create a favorable environment for replication, largely by deregulating cell cycle checkpoints. This review focuses on our current understanding of the molecular aspects of cell cycle regulation that are often targeted by viruses. Further study of their interactions should provide fundamental insights into cell cycle regulation and improve our ability to exploit these viruses.

HIV-1 Vpr hijacks EDD-DYRK2-DDB1DCAF1 to disrupt centrosome homeostasis

Viruses exploit the host cell machinery for their own profit. To evade innate immune sensing and promote viral replication, HIV type 1 (HIV-1) subverts DNA repair regulatory proteins and induces G2/M arrest. The preintegration complex of HIV-1 is known to traffic along microtubules and accumulate near the microtubule-organizing center. The centrosome is the major microtubule-organizing center in most eukaryotic cells, but precisely how HIV-1 impinges on centrosome biology remains poorly understood. We report here that the HIV-1 accessory protein viral protein R (Vpr) localized to the centrosome through binding to DCAF1, forming a complex with the ubiquitin ligase EDD-DYRK2-DDB1DCAF1 and Cep78, a resident centrosomal protein previously shown to inhibit EDD-DYRK2-DDB1DCAF1 Vpr did not affect ubiquitination of Cep78. Rather, it enhanced ubiquitination of an EDD-DYRK2-DDB1DCAF1 substrate, CP110, leading to its degradation, an effect that could be overcome by Cep78 expression. The down-regulation of CP110 and elongation of centrioles provoked by Vpr were independent of G2/M arrest. Infection of T lymphocytes with HIV-1, but not with HIV-1 lacking Vpr, promoted CP110 degradation and centriole elongation. Elongated centrioles recruited more γ-tubulin to the centrosome, resulting in increased microtubule nucleation. Our results suggest that Vpr is targeted to the centrosome where it hijacks a ubiquitin ligase, disrupting organelle homeostasis, which may contribute to HIV-1 pathogenesis.

Differential abundance and transcription of 14-3-3 proteins during vegetative growth and sexual reproduction in budding yeast

14-3-3 is a family of relatively low molecular weight, acidic, dimeric proteins, conserved from yeast to metazoans including humans. Apart from their role in diverse cellular processes, these proteins are also known for their role in several clinical implications. Present proteomic and biochemical comparison showed increased abundance and differential phosphorylation of these proteins in meiotic cells. Double deletion of bmh1^−/−bmh2^−/− leads to complete absence of sporulation with cells arrested at G₁/S phase while further incubation of cells in sporulating media leads to cell death. In silico analysis showed the presence of 14-3-3 interacting motifs in bonafide members of kinetochore complex (KC) and spindle pole body (SPB), while present cell biological data pointed towards the possible role of yeast Bmh1/2 in regulating the behaviour of KC and SPB. We further showed the involvement of 14-3-3 in segregation of genetic material and expression of human 14-3-3β/α was able to complement the function of endogenous 14-3-3 protein even in the complex cellular process like meiosis. Our present data also established haplosufficient nature of BMH1/2. We further showed that proteins synthesized during mitotic growth enter meiotic cells without de novo synthesis except for meiotic-specific proteins required for induction and meiotic progression in Saccharomyces cerevisiae.

An account of fungal 14-3-3 proteins

14-3-3s are a group of relatively low molecular weight, acidic, dimeric, protein(s) conserved from single-celled yeast to multicellular vertebrates including humans. Despite lacking catalytic activity, these proteins have been shown to be involved in multiple cellular processes. Apart from their role in normal cellular physiology, recently these proteins have been implicated in various medical consequences. In this present review, fungal 14-3-3 protein localization, interactions, transcription, regulation, their role in the diverse cellular process including DNA duplication, cell cycle, protein trafficking or secretion, apoptosis, autophagy, cell viability under stress, gene expression, spindle positioning, role in carbon metabolism have been discussed. In the end, I also highlighted various roles of yeasts 14-3-3 proteins in tabular form. Thus this review with primary emphasis on yeast will help in appreciating the significance of 14-3-3 proteins in cell physiology.

The 14-3-3 protein Bmh1 functions in the spindle position checkpoint by breaking Bfa1 asymmetry at yeast centrosomes

Phosphorylation of Bfa1 by Kin4 creates a docking site on Bfa1 for the 14-3-3 family protein Bmh1, which in turn weakens Bfa1–centrosome association and promotes symmetric Bfa1 localization to engage the spindle position checkpoint.

In addition to their well-known role in microtubule organization, centrosomes function as signaling platforms and regulate cell cycle events. An important example of such a function is the spindle position checkpoint (SPOC) of budding yeast. SPOC is a surveillance mechanism that ensures alignment of the mitotic spindle along the cell polarity axis. Upon spindle misalignment, phosphorylation of the SPOC component Bfa1 by Kin4 kinase engages the SPOC by changing the centrosome localization of Bfa1 from asymmetric (one centrosome) to symmetric (both centrosomes). Here we show that, unexpectedly, Kin4 alone is unable to break Bfa1 asymmetry at yeast centrosomes. Instead, phosphorylation of Bfa1 by Kin4 creates a docking site on Bfa1 for the 14-3-3 family protein Bmh1, which in turn weakens Bfa1–centrosome association and promotes symmetric Bfa1 localization. Consistently, BMH1-null cells are SPOC deficient. Our work thus identifies Bmh1 as a new SPOC component and refines the molecular mechanism that breaks Bfa1 centrosome asymmetry upon SPOC activation.

HIV-1 Vpr-a still "enigmatic multitasker"

Like other HIV-1 auxiliary proteins, Vpr is conserved within all the human (HIV-1, HIV-2) and simian (SIV) immunodeficiency viruses. However, Vpr and homologous HIV-2, and SIV Vpx are the only viral auxiliary proteins specifically incorporated into virus particles through direct interaction with the Gag precursor, indicating that this presence in the core of the mature virions is mainly required for optimal establishment of the early steps of the virus life cycle in the newly infected cell. In spite of its small size, a plethora of effects and functions have been attributed to Vpr, including induction of cell cycle arrest and apoptosis, modulation of the fidelity of reverse transcription, nuclear import of viral DNA in macrophages and other non-dividing cells, and transcriptional modulation of viral and host cell genes. Even if some more recent studies identified a few cellular targets that HIV-1 Vpr may utilize in order to perform its different tasks, the real role and functions of Vpr during the course of natural infection are still enigmatic. In this review, we will summarize the main reported functions of HIV-1 Vpr and their significance in the context of the viral life cycle.

Scaffold functions of 14-3-3 adaptors in B cell immunoglobulin class switch DNA recombination

Class switch DNA recombination (CSR) of the immunoglobulin heavy chain (IgH) locus crucially diversifies antibody biological effector functions. CSR involves the induction of activation-induced cytidine deaminase (AID) expression and AID targeting to switch (S) regions by 14-3-3 adaptors. 14-3-3 adaptors specifically bind to 5'-AGCT-3' repeats, which make up for the core of all IgH locus S regions. They selectively target the upstream and downstream S regions that are set to undergo S-S DNA recombination. We hypothesized that 14-3-3 adaptors function as scaffolds to stabilize CSR enzymatic elements on S regions. Here we demonstrate that all seven 14-3-3β, 14-3-3ε, 14-3-3γ, 14-3-3η, 14-3-3σ, 14-3-3τ and 14-3-3ζ adaptors directly interacted with AID, PKA-Cα (catalytic subunit) and PKA-RIα (regulatory inhibitory subunit) and uracil DNA glycosylase (Ung). 14-3-3 adaptors, however, did not interact with AID C-terminal truncation mutant AIDΔ(180-198) or AIDF193A and AIDL196A point-mutants (which have been shown not to bind to S region DNA and fail to mediate CSR). 14-3-3 adaptors colocalized with AID and replication protein A (RPA) in B cells undergoing CSR. 14-3-3 and AID binding to S region DNA was disrupted by viral protein R (Vpr), an accessory protein of human immunodeficiency virus type-1 (HIV-1), which inhibited CSR without altering AID expression or germline IH-CH transcription. Accordingly, we demonstrated that 14-3-3 directly interact with Vpr, which in turn, also interact with AID, PKA-Cα and Ung. Altogether, our findings suggest that 14-3-3 adaptors play important scaffold functions and nucleate the assembly of multiple CSR factors on S regions. They also show that such assembly can be disrupted by a viral protein, thereby allowing us to hypothesize that small molecule compounds that specifically block 14-3-3 interactions with AID, PKA and/or Ung can be used to inhibit unwanted CSR.

YWHAE/14-3-3ε: a potential novel genetic risk factor and CSF biomarker for HIV neurocognitive impairment

YWHAE (14-3-3ε) protein levels are considered to be a reliable biomarker for neurodegeneration. The YWHAE protein interacts both directly and indirectly with human immunodeficiency virus (HIV) accessory proteins, leading to cell death. The purpose of this study was to examine the relationship between YWHAE polymorphisms and HIV-associated neurocognitive disorder (HAND) and the relationship between YWHAE protein levels and HAND. A cross-sectional study using random samples of HIV-seropositive (n = 20) and HIV-seronegative (controls) (n = 16) women from the Hispanic-Latino Longitudinal Cohort of Women was conducted. Individuals who are HIV-seropositive and heterozygous at the rs4790084/rs1204828 loci in the YWHAE gene were 3× more likely to display reduced cognitive functioning, to have received a HAND diagnosis, and to have less YHWAE protein expressed than homozygotes. Western blots from cerebral spinal fluid indicate that the HIV-seropositive women with HAND expressed 4.5× less YWHAE compared to HIV-seropositive cognitively normal women (94 % sensitivity, 84 % specificity; HIV-seropositive vs. controls). Therefore, polymorphism in YWHAE may be a genetic risk factor for HAND and levels of YWHAE protein are a likely biomarker for neurocognitive status in HIV-seropositive women.

14-3-3s are potential biomarkers for HIV-related neurodegeneration

Over the last decade, it has become evident that 14-3-3 proteins are essential for primary cell functions. These proteins are abundant throughout the body, including the central nervous system and interact with other proteins in both cell cycle and apoptotic pathways. Examination of cerebral spinal fluid in humans suggests that 14-3-3s including 14-3-3ε (YWHAE) are up-regulated in several neurological diseases, and loss or duplication of the YWHAE gene leads to Miller-Dieker syndrome. The goal of this review is to examine the utility of 14-3-3s as a marker of human immune deficiency virus (HIV)-dependent neurodegeneration and also as a tool to track disease progression. To that end, we describe mechanisms implicating 14-3-3s in neurological diseases and summarize evidence of its interactions with HIV accessory and co-receptor proteins.

Exposed hydrophobic residues in human immunodeficiency virus type 1 Vpr helix-1 are important for cell cycle arrest and cell death

The human immunodeficiency virus type 1 (HIV-1) accessory protein viral protein R (Vpr) is a major determinant for virus-induced G2/M cell cycle arrest and cytopathicity. Vpr is thought to perform these functions through the interaction with partner proteins. The NMR structure of Vpr revealed solvent exposed hydrophobic amino acids along helices 1 and 3 of Vpr, which could be putative protein binding domains. We previously showed that the hydrophobic patch along helix-3 was important for G2/M blockade and cytopathicity. Mutations of the exposed hydrophobic residues along helix-1 were found to reduce Vpr-induced cell cycle arrest and cell death as well. The levels of toxicity during virion delivery of Vpr correlated with G2/M arrest. Thus, the exposed hydrophobic amino acids in the amino-terminal helix-1 are important for the cell cycle arrest and cytopathicity functions of Vpr.

Human immunodeficiency virus type 1 Vif causes dysfunction of Cdk1 and CyclinB1: implications for cell cycle arrest

The two major cytopathic factors in human immunodeficiency virus type 1 (HIV-1), the accessory proteins viral infectivity factor (Vif) and viral protein R (Vpr), inhibit cell-cycle progression at the G2 phase of the cell cycle. Although Vpr-induced blockade and the associated T-cell death have been well studied, the molecular mechanism of G2 arrest by Vif remains undefined. To elucidate how Vif induces arrest, we infected synchronized Jurkat T-cells and examined the effect of Vif on the activation of Cdk1 and CyclinB1, the chief cell-cycle factors for the G2 to M phase transition. We found that the characteristic dephosphorylation of an inhibitory phosphate on Cdk1 did not occur in infected cells expressing Vif. In addition, the nuclear translocation of Cdk1 and CyclinB1 was disregulated. Finally, Vif-induced cell cycle arrest was correlated with proviral expression of Vif. Taken together, our results suggest that Vif impairs mitotic entry by interfering with Cdk1-CyclinB1 activation.

HIV-1 viral protein r: from structure to function

The viral protein r (Vpr) of HIV-1 binds several host proteins leading to pleiotropic functions, such as G2/M cell cycle arrest, apoptosis induction and gene transactivation. Vpr is encapsidated through the Gag C-terminus into the nascent viral particles, suggesting that Vpr plays several important functions in the early stages of the viral lifecycle. In this regard, Vpr interacts with nucleic acids and membranes to facilitate the preintegration complex migration and incorporation into the nucleus of nondividing cells. Thus, Vpr has to recruit several host and viral factors to promote its functions during HIV-1 pathogenesis. This article focuses on its interacting partners by giving an overview of the functional outcome of the different Vpr complexes, as well as the structural determinants of Vpr required for its binding properties.

Functional integrity of naturally occurring mutants of HIV-1 subtype C Vpr

HIV-1 Vpr, an accessory protein with multiple functions, is involved in the induction of apoptosis, cell cycle G2 arrest, and modulation of gene expression. Many functions of this protein have been documented for the wild-type subtype B Vpr, however the functionality of other subtypes has not sufficiently been addressed. In this study, the functionality of Subtype B Vpr, 6 subtype C mutant Vpr proteins and the consensus sequence of subtype C Vpr were compared with each other. All the subtype B and C Vpr proteins localized to the nucleus of human 293T cells. Subtype C Vpr proteins induced cell cycle G2 arrest in a lower proportion of human 293T cells compared to subtype B Vpr. Subtype B and the naturally mutant Vpr proteins induced apoptosis in a similar manner, ranging from 95.33% to 98.64%. However, an artificially designed Vpr protein containing the consensus sequences of subtype C Vpr indicated a reduced ability in induction of apoptosis. The study of mRNA profile of the transfected cells indicated that all Vpr proteins modulated the apoptotic genes triggering the intrinsic pathway of apoptosis. Our results indicate that subtype C Vpr is able to exert the same functions previously reported for subtype B Vpr. Most natural mutations in Vpr not only do not disturb the functions of the protein but also potentiate the protein for an increased functionality. The natural mutations of Vpr may thus not always be regarded as defective mutations. The study suggests the adaptive role of the natural mutations commonly found in subtype C Vpr.

Protein kinase A phosphorylation activates Vpr-induced cell cycle arrest during human immunodeficiency virus type 1 infection

Infection with human immunodeficiency virus type 1 (HIV-1) causes an inexorable depletion of CD4(+) T cells. The loss of these cells is particularly pronounced in the mucosal immune system during acute infection, and the data suggest that direct viral cytopathicity is a major factor. Cell cycle arrest caused by the HIV-1 accessory protein Vpr is strongly correlated with virus-induced cell death, and phosphorylation of Vpr serine 79 (S79) is required to activate G(2)/M cell cycle blockade. However, the kinase responsible for phosphorylating Vpr remains unknown. Our bioinformatic analyses revealed that S79 is part of a putative phosphorylation site recognized by protein kinase A (PKA). We show here that PKA interacts with Vpr and directly phosphorylates S79. Inhibition of PKA activity during HIV-1 infection abrogates Vpr cell cycle arrest. These findings provide new insight into the signaling event that activates Vpr cell cycle arrest, ultimately leading to the death of infected T cells.

Vpr and its interactions with cellular proteins

Like most viral regulatory proteins, HIV-1 Vpr and homologous proteins from primate lentiviruses are small and multifunctional. They are associated with a plethora of effects and functions, including induction of cell cycle arrest in the G(2) phase, induction of apoptosis, transactivation, enhancement of the fidelity of reverse transcription, and nuclear import of viral DNA in macrophages and other nondividing cells. This review focuses on the cellular proteins that have been reported to interact with Vpr and their significance with respect to the known functions and effects of Vpr on cells and on viral replication.

Endogenous HIV-1 Vpr-mediated apoptosis and proteome alteration of human T-cell leukemia virus-1 transformed C8166 cells

HIV-1 viral protein R (Vpr) can induce cell cycle arrest and cell death, and may be beneficial in cancer therapy to suppress malignantly proliferative cell types, such as adult T-cell leukemia (ATL) cells. In this study, we examined the feasibility of employing the HIV-vpr gene, via targeted gene transfer, as a potential new therapy to kill ATL cells. We infected C8166 cells with a recombinant adenovirus carrying both vpr and GFP genes (rAd-vpr), as well as the vector control virus (rAd-vector). G(2)/M phase cell cycle arrest was observed in the rAd-vpr infected cells. Typical characteristics of apoptosis were detected in rAd-vpr infected cells, including sub-diploid peak exhibition in DNA content assay, the Hoechst 33342 accumulation, apoptotic body formation, mitochondrial membrane potential and plasma membrane integrity loss. The proteomic assay revealed apoptosis related protein changes, exhibiting the regulation of caspase-3 activity indicator proteins (vimentin and Rho GDP-dissociation inhibitor 2), mitochondrial protein (prohibitin) and other regulatory proteins. In addition, the up-regulation of anti-inflammatory redox protein, thioredoxin, was identified in the rAd-vpr infected group. Further supporting these findings, the increase of caspase 3&7 activity in the rAd-vpr infected group was observed. In conclusion, endogenous Vpr is able to kill HTLV-1 transformed C8166 cells, and may avoid the risks of inducing severe inflammatory responses through apoptosis-inducing and anti-inflammatory activities.