Metformin Treatment Leads to Increased HIV Transcription and Gene Expression through Increased CREB Phosphorylation and Recruitment to the HIV LTR Promoter

Antiretroviral therapy has effectively suppressed HIV infection and replication and prolonged the lifespan of HIV-infected individuals. In the meantime, various complications including type 2 diabetes associated with the long-term antiviral therapy have shown steady increases. Metformin has been the front-line anti-hyperglycemic drug of choice and the most widely prescribed medication for the treatment of type 2 diabetes. However, little is known about the effects of Metformin on HIV infection and replication. In this study, we showed that Metformin treatment enhanced HIV gene expression and transcription in HIV-transfected 293T and HIV-infected Jurkat and human PBMC. Moreover, we demonstrated that Metformin treatment resulted in increased CREB expression and phosphorylation, and TBP expression. Furthermore, we showed that Metformin treatment increased the recruitment of phosphorylated CREB and TBP to the HIV LTR promoter. Lastly, we showed that inhibition of CREB phosphorylation/activation significantly abrogated Metformin-enhanced HIV gene expression. Taken together, these results demonstrated that Metformin treatment increased HIV transcription, gene expression, and production through increased CREB phosphorylation and recruitment to the HIV LTR promoter. These findings may help design the clinical management plan and HIV cure strategy of using Metformin to treat type 2 diabetes, a comorbidity with an increasing prevalence, in people living with HIV.

A Unique Robust Dual-Promoter-Driven and Dual-Reporter-Expressing SARS-CoV-2 Replicon: Construction and Characterization

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2, SARS2) remains a great global health threat and demands identification of more effective and SARS2-targeted antiviral drugs, even with successful development of anti-SARS2 vaccines. Viral replicons have proven to be a rapid, safe, and readily scalable platform for high-throughput screening, identification, and evaluation of antiviral drugs against positive-stranded RNA viruses. In the study, we report a unique robust HIV long terminal repeat (LTR)/T7 dual-promoter-driven and dual-reporter firefly luciferase (fLuc) and green fluorescent protein (GFP)-expressing SARS2 replicon. The genomic organization of the replicon was designed with quite a few features that were to ensure the replication fidelity of the replicon, to maximize the expression of the full-length replicon, and to offer the monitoring flexibility of the replicon replication. We showed the success of the construction of the replicon and expression of reporter genes fLuc and GFP and SARS structural N from the replicon DNA or the RNA that was in vitro transcribed from the replicon DNA. We also showed detection of the negative-stranded genomic RNA (gRNA) and subgenomic RNA (sgRNA) intermediates, a hallmark of replication of positive-stranded RNA viruses from the replicon. Lastly, we showed that expression of the reporter genes, N gene, gRNA, and sgRNA from the replicon was sensitive to inhibition by Remdesivir. Taken together, our results support use of the replicon for identification of anti-SARS2 drugs and development of new anti-SARS strategies targeted at the step of virus replication.

Tat expression led to increased histone 3 tri-methylation at lysine 27 and contributed to HIV latency in astrocytes through regulation of MeCP2 and Ezh2 expression

Astrocytes are susceptible to HIV infection and potential latent HIV reservoirs. Tat is one of three abundantly expressed HIV early genes in HIV-infected astrocytes and has been shown to be a major pathogenic factor for HIV/neuroAIDS. In this study, we sought to determine if and how Tat expression would affect HIV infection and latency in astrocytes. Using the glycoprotein from vesicular stomatitis virus-pseudotyped red-green HIV (RGH) reporter viruses, we showed that HIV infection was capable of establishing HIV latency in astrocytes. We also found that Tat expression decreased the generation of latent HIV-infected cells. Activation of latent HIV-infected astrocytes showed that treatment of GSK126, a selective inhibitor of methyltransferase enhancer of zeste homolog 2 (Ezh2) that is specifically responsible for tri-methylation of histone 3 lysine 27 (H3K27me3), led to activation of significantly more latent HIV-infected Tat-expressing astrocytes. Molecular analysis showed that H3K27me3, Ezh2, MeCP2, and Tat all exhibited a similar bimodal expression kinetics in the course of HIV infection and latency in astrocytes, although H3K27me3, Ezh2, and MeCP2 were expressed higher in Tat-expressing astrocytes and their expression were peaked immediately preceding Tat expression. Subsequent studies showed that Tat expression alone was sufficient to induce H3K27me3 expression, likely through its regulation of Ezh2 and MeCP2 expression. Taken together, these results showed for the first time that Tat expression induced H3K27me3 expression and contributed to HIV latency in astrocytes and suggest a new role and novel mechanism for Tat in HIV latency.

Regulation of Constitutive Tip110 Expression in Human Cord Blood CD34+ Cells Through Selective Usage of the Proximal and Distal Polyadenylation Sites Within the 3'Untranslated Region

Tip110 plays important roles for stem cell pluripotency and hematopoiesis. However, little is known about the regulatory mechanisms of Tip110 expression in this process. In this study, we first showed that constitutive Tip110 expression was cell proliferation and differentiation dependent and self-regulated in both human cord blood CD34⁺ cells. Using a series of molecular techniques, we found that ectopic Tip110 expression led to increased constitutive Tip110 expression through its 3'-untranslated region (3'UTR), specifically through preferential usage of proximal polyadenylation sites within its 3'UTR in cells, including human cord blood CD34⁺ cells, which indeed led to an increased number of CD34⁺ cells during differentiation of those cells. Lastly, we showed that Tip110 protein interacted with cleavage stimulation factor 64 (CstF64) protein and that more CstF64 was recruited to the promixal polyadenylation site than the distal polyadenylation site within its 3'UTR. These finding together demonstrates that constitutive Tip110 expression is regulated, at least in part, through its interaction with CstF64, recruitment of CstF64 to, and selective usage of those two polyadenylation sites within its 3'UTR.

Establishment of stable HeLa cell lines expressing enzymatically active hepatitis C virus RNA polymerase

The hepatitis C virus RNA polymerase (NS5B) is strictly required for viral replication and thus represents an attractive target for antiviral drug development. In this study, stable HeLa cell lines with an integrated NS5B gene were selected by G418 and then confirmed by genome PCR. Subsequently, transcription and expression of the integrated NS5B genes were demonstrated by RT-PCR and Western blot analysis. Further analysis demonstrated enzymatic activity of the expressed NS5B polymerase. The stable HeLa cell lines should be useful for the identification of NS5B inhibitors and for studying the mechanisms of HCV replication.

Gene expression profiles of HeLa Cells impacted by hepatitis C virus non-structural protein NS4B

By a cDNA array representing 2308 signal transduction-related genes, we studied the expression profiles of HeLa cells stably transfected by Hepatitis C virus nonstructural protein 4B (HCV-NS4B). The alterations of the expression of four genes were confirmed by real-time quantitative RTPCR; and the aldo-keto reductase family 1, member C1 (AKR1C1) enzyme activity was detected in HCV-NS4B transiently transfected HeLa cells and Huh-7, a human hepatoma cell line. Of the 2,308 genes we examined, 34 were up-regulated and 56 were down-regulated. These 90 genes involved oncogenes, tumor suppressors, cell receptors, complements, adhesions, transcription and translation, cytoskeleton and cellular stress. The expression profiling suggested that multiple regulatory pathways were affected by HCV-NS4B directly or indirectly. And since these genes are related to carcinogenesis, host defense system and cell homeostatic mechanism, we can conclude that HCV-NS4B could play some important roles in the pathogenesis mechanism of HCV.

Two cis-acting elements in negative RNA strand of Hepatitis C virus involved in synthesis of positive RNA strand in vitro

Sequences at the 3'-ends of both positive and negative strands of Hepatitis C virus (HCV) RNA harbor cis-acting elements required for RNA replication. However, little is known about the properties of the negative RNA strand as a template for the synthesis of positive RNA strand. In this study, a purified recombinant HCV RNA-dependent RNA polymerase (RdRp) was used to investigate the synthesis of positive RNA strand using the 3'-terminal region of negative RNA strand ((-)3'T RNA) as template. A mutagenesis analysis was performed to evaluate the role of the 3'-proximal stem-loop and the first 3'-cytidylate (3'C) of the negative RNA strand in the synthesis of the positive RNA strand. A negative RNA strand of wild type (wt) HCV as template was able to direct the synthesis of a full-length positive RNA strand. Deletion of the 3'-proximal stem-loop resulted in an approximately 90% decrease in RNA synthesis. Disruption of the 3'-proximal stem-loop structure by nucleotide substitutions led to a 70-80% decrease in RNA synthesis. However, the restoration of the stem-loop by compensatory mutations in the stem region restored also the RNA synthesis. Likewise, the deletion or substitution of the first 3'C by guanylate (G) led to a 90% decrease in the RNA synthesis; while the substitution by adenylate (A) or uridylate (U) resulted in a 60-80% decrease in the RNA synthesis only. These findings demonstrate that the 3'-proximal stem-loop and the first 3'C of the negative RNA strand of HCV are two cis-acting elements involved in the synthesis of the positive RNA strand.

Possible mode of action of antiherpetic activities of a proteoglycan isolated from the mycelia of Ganoderma lucidum in vitro

A bioactive fraction (GLPG) was extracted and purified from the mycelia of Ganoderma lucidum by EtOH precipitation and DEAE-cellulose column chromatography. GLPG was a proteoglycan and had a carbohydrate:protein ratio of 10.4:1. Its antiviral activities against herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) were investigated by the cytopathic effect (CPE) inhibition assay in cell culture. This kind of polysaccharide inhibited the development of the cytopathic effect in dose-dependent manner in HSV-infected cells, moreover did not show any cytotoxic effects on cells even when a concentration was as high as 2000 microg/ml. In order to study the possible mode of action of the antiviral activity of GLPG, cells were treated with GLPG before, during and after infection, and the viral titers in the supernatant of cell culture 48 h post-infection were tested by TCID(50) assay. The antiviral effects in pre-treated and treated during virus infection with GLPG were more remarkable than the treatment of post-infection. Although the precise mechanism has yet to be defined, our work suggested that GLPG inhibits viral replication by interfering with the early events of viral adsorption and entry into target cells. Thus, this proteoglycan seems to be a potential candidate for anti-HSV agents.