SLC4A11 mediates ammonia import and promotes cancer stemness in hepatocellular carcinoma.

End-stage liver disease is marked by portal hypertension, systemic elevations in ammonia, and development of hepatocellular carcinoma (HCC). While these clinical consequences of cirrhosis are well described, it remains poorly understood whether hepatic insufficiency and the accompanying elevations in ammonia contribute to HCC carcinogenesis. Using preclinical models, we discovered that ammonia entered the cell through the transporter SLC4A11 and served as a nitrogen source for amino acid and nucleotide biosynthesis.

Interplay of RAP2 GTPase and the cytoskeleton in Hippo pathway regulation.

The Hippo signaling is instrumental in regulating organ size, regeneration, and carcinogenesis. The cytoskeleton emerges as a primary Hippo signaling modulator. Its structural alterations in response to environmental and intrinsic stimuli control Hippo signaling pathway activity.

Interplay of RAP2 GTPase and the cytoskeleton in Hippo pathway regulation.

The Hippo signaling is instrumental in regulating organ size, regeneration, and carcinogenesis. The cytoskeleton emerges as a primary Hippo signaling modulator. Its structural alterations in response to environmental and intrinsic stimuli control Hippo kinase cascade activity.

A Rapid Translational Immune Response Program in CD8 Memory T Lymphocytes.

The activation of memory T cells is a very rapid and concerted cellular response that requires coordination between cellular processes in different compartments and on different time scales. In this study, we use ribosome profiling and deep RNA sequencing to define the acute mRNA translation changes in CD8 memory T cells following initial activation events. We find that initial translation enables subsequent events of human and mouse T cell activation and expansion.

Frequent 4EBP1 Amplification Induces Synthetic Dependence on FGFR Signaling in Cancer.

The eIF4E translation initiation factor has oncogenic properties and concordantly, the inhibitory eIF4E-binding protein (4EBP1) is considered a tumor suppressor. The exact molecular effects of 4EBP1 activation in cancer are still unknown. Surprisingly, 4EBP1 is a target of genomic copy number gains (Chr.

Targeting eIF4A-Dependent Translation of KRAS Signaling Molecules.

Pancreatic adenocarcinoma (PDAC) epitomizes a deadly cancer driven by abnormal KRAS signaling. Here, we show that the eIF4A RNA helicase is required for translation of key KRAS signaling molecules and that pharmacological inhibition of eIF4A has single-agent activity against murine and human PDAC models at safe dose levels. EIF4A was uniquely required for the translation of mRNAs with long and highly structured 5' untranslated regions, including those with multiple G-quadruplex elements.

NRF2 Activation Confers Resistance to eIF4A Inhibitors in Cancer Therapy.

Inhibition of the eIF4A RNA helicase with silvestrol and related compounds is emerging as a powerful anti-cancer strategy. We find that a synthetic silvestrol analogue (CR-1-31 B) has nanomolar activity across many cancer cell lines. It is especially active against aggressive MYC/BCL2 B cell lymphomas and this likely reflects the eIF4A-dependent translation of both MYC and BCL2.

The Oncogenic Action of NRF2 Depends on De-glycation by Fructosamine-3-Kinase.

The NRF2 transcription factor controls a cell stress program that is implicated in cancer and there is great interest in targeting NRF2 for therapy. We show that NRF2 activity depends on Fructosamine-3-kinase (FN3K)-a kinase that triggers protein de-glycation. In its absence, NRF2 is extensively glycated, unstable, and defective at binding to small MAF proteins and transcriptional activation.

Characterization of a set of tumor suppressor microRNAs in T cell acute lymphoblastic leukemia.

The posttranscriptional control of gene expression by microRNAs (miRNAs) is highly redundant, and compensatory effects limit the consequences of the inactivation of individual miRNAs. This implies that only a few miRNAs can function as effective tumor suppressors. It is also the basis of our strategy to define functionally relevant miRNA target genes that are not under redundant control by other miRNAs.

RNA G-quadruplexes cause eIF4A-dependent oncogene translation in cancer.

The translational control of oncoprotein expression is implicated in many cancers. Here we report an eIF4A RNA helicase-dependent mechanism of translational control that contributes to oncogenesis and underlies the anticancer effects of silvestrol and related compounds. For example, eIF4A promotes T-cell acute lymphoblastic leukaemia development in vivo and is required for leukaemia maintenance.

RNA silencing as a cellular defense against HIV-1 infection: progress and issues.

MicroRNAs (miRNAs) are known to have a role in gene regulation that is closely integrated into the pathways that control virtually all fundamental cell processes of growth, differentiation, metabolism, and death. Whether silencing RNAs and the cellular pathways that generate them are also used in antiviral defense in higher eukaryotes, as they are in plants and lower eukaryotes, has been the subject of much study. Results to date point to a complex interplay between viruses and vertebrate host cells that can vary considerably among different viruses.

Polycistronic expression of interfering RNAs from RNA polymerase III promoters.

In many RNA silencing applications, there is a benefit to expressing multiple interfering RNAs simultaneously. This can be achieved by using a single RNA polymerase II promoter to express multiple micro(mi)RNA-formatted interfering RNAs that are arranged in a polycistronic cluster, mimicking the organization of naturally clustered, endogenous miRNAs. While RNA pol III promoters are often used to express individual short hairpin (sh) RNAs, we have recently shown that pol III promoters can also be used to drive polycistronic expression of miRNA-formatted interfering RNAs.

The cellular TAR RNA binding protein, TRBP, promotes HIV-1 replication primarily by inhibiting the activation of double-stranded RNA-dependent kinase PKR.

The TAR RNA binding protein, TRBP, is a cellular double-stranded RNA (dsRNA) binding protein that can promote the replication of HIV-1 through interactions with the viral TAR element as well as with cellular proteins that affect the efficiency of translation of viral transcripts. The structured TAR element, present on all viral transcripts, can impede efficient translation either by sterically blocking access of translation initiation factors to the 5'-cap or by activating the dsRNA-dependent kinase, PKR. Several mechanisms by which TRBP can facilitate translation of viral transcripts have been proposed, including the binding and unwinding of TAR and the suppression of PKR activation.

A re-examination of global suppression of RNA interference by HIV-1.

The nature of the interaction between replicating HIV-1 and the cellular RNAi pathway has been controversial, but it is clear that it can be complex and multifaceted. It has been proposed that the interaction is bi-directional, whereby cellular silencing pathways can restrict HIV-1 replication, and in turn, HIV-1 can suppress silencing pathways. Overall suppression of RNAi has been suggested to occur via direct binding and inhibition of Dicer by the HIV-1 Tat protein or through sequestration of TRBP, a Dicer co-factor, by the structured TAR element of HIV-1 transcripts.

Expression of interfering RNAs from an HIV-1 Tat-inducible chimeric promoter.

The therapeutic value of antiviral interfering RNAs could be improved by technologies that limit their expression to the infected cell population. The HIV-1 Tat-inducible viral LTR and LTR-containing chimeric promoters have previously been used to drive expression of antiviral RNAs and proteins directed against HIV-1. Here, we characterize an alternative promoter, consisting of a chicken β-actin core promoter fused to the viral TAR element, for the conditional expression of interfering RNAs.