Melanoma RBPome identification reveals PDIA6 as an unconventional RNA-binding protein involved in metastasis.

RNA-binding proteins (RBPs) have been relatively overlooked in cancer research despite their contribution to virtually every cancer hallmark. Here, we use RNA interactome capture (RIC) to characterize the melanoma RBPome and uncover novel RBPs involved in melanoma progression. Comparison of RIC profiles of a non-tumoral versus a metastatic cell line revealed prevalent changes in RNA-binding capacities that were not associated with changes in RBP levels.

Coordinated post-transcriptional control of oncogene-induced senescence by UNR/CSDE1.

Oncogene-induced senescence (OIS) is a form of stable cell-cycle arrest arising in response to oncogenic stimulation. OIS must be bypassed for transformation, but the mechanisms of OIS establishment and bypass remain poorly understood, especially at the post-transcriptional level. Here, we show that the RNA-binding protein UNR/CSDE1 enables OIS in primary mouse keratinocytes.

Cold-inducible RNA binding protein promotes breast cancer cell malignancy by regulating Cystatin C levels.

Cold-inducible RNA binding protein (CIRBP) is a stress-responsive protein that promotes cancer development and inflammation. Critical to most CIRBP functions is its capacity to bind and posttranscriptionally modulate mRNA. However, a transcriptome-wide analysis of CIRBP mRNA targets in cancer has not yet been performed.

Hrp48 and eIF3d contribute to msl-2 mRNA translational repression.

Translational repression of msl-2 mRNA in females of Drosophila melanogaster is an essential step in the regulation of X-chromosome dosage compensation. Repression is orchestrated by Sex-lethal (SXL), which binds to both untranslated regions (UTRs) of msl-2 and inhibits translation initiation by poorly understood mechanisms. Here we identify Hrp48 as a SXL co-factor.

Dicer-2 promotes mRNA activation through cytoplasmic polyadenylation.

Cytoplasmic polyadenylation is a widespread mechanism to regulate mRNA translation. In vertebrates, this process requires two sequence elements in target 3' UTRs: the U-rich cytoplasmic polyadenylation element and the AAUAAA hexanucleotide. In , cytoplasmic polyadenylation of mRNA occurs independently of these canonical elements and requires a machinery that remains to be characterized.

Cytoplasmic polyadenylation assays.

Basic research in Drosophila melanogaster has benefited from a plethora of powerful genetics tools. Detailed biochemical analysis, however, has often been difficult due to the lack of in vitro systems that faithfully recapitulate the observations made in vivo. In the field of posttranscriptional regulation, the recent establishment of robust in vitro systems from embryo and ovary material has fueled the mechanistic understanding of a variety of processes.

Cytoplasmic polyadenylation and translational control.

Cytoplasmic polyadenylation is the process by which dormant, translationally inactive mRNAs become activated via the elongation of their poly(A) tails in the cytoplasm. This process is regulated by the conserved cytoplasmic polyadenylation element binding (CPEB) protein family. Recent studies have advanced our understanding of the molecular code that dictates the timing of CPEB-mediated poly(A) tail elongation and the extent of translational activation.

A novel, noncanonical mechanism of cytoplasmic polyadenylation operates in Drosophila embryogenesis.

Cytoplasmic polyadenylation is a widespread mechanism to regulate mRNA translation that requires two sequences in the 3' untranslated region (UTR) of vertebrate substrates: the polyadenylation hexanucleotide, and the cytoplasmic polyadenylation element (CPE). Using a cell-free Drosophila system, we show that these signals are not relevant for Toll polyadenylation but, instead, a "polyadenylation region" (PR) is necessary. Competition experiments indicate that PR-mediated polyadenylation is required for viability and is mechanistically distinct from the CPE/hexanucleotide-mediated process.

Neutral sphingomyelinase-induced ceramide triggers germinal vesicle breakdown and oxidant-dependent apoptosis in Xenopus laevis oocytes.

Ceramide regulates many cellular processes, including cell growth, differentiation, and apoptosis. Although the effects of exogenous bacterial neutral sphingomyelinase (SMase) in Xenopus laevis oocytes have been investigated, its microinjection into oocytes has not been reported previously. Thus, we compared the incubation versus microinjection of the neutral Bacillus cereus sphingomyelinase (bSMase) to examine whether the topology of ceramide generation determines its effects on the fate of oocytes.

Drosophila UNR is required for translational repression of male-specific lethal 2 mRNA during regulation of X-chromosome dosage compensation.

The inhibition of male-specific lethal 2 (msl-2) mRNA translation by the RNA-binding protein sex-lethal (SXL) is an essential regulatory step for X-chromosome dosage compensation in Drosophila melanogaster. The mammalian upstream of N-ras (UNR) protein has been implicated in the regulation of mRNA stability and internal ribosome entry site (IRES)-dependent mRNA translation. Here we have identified the Drosophila homolog of mammalian UNR as a cofactor required for SXL-mediated repression of msl-2 translation.

Sensitivity of the 2-oxoglutarate carrier to alcohol intake contributes to mitochondrial glutathione depletion.

The mitochondrial pool of reduced glutathione (mGSH) is known to play a protective role against liver injury and cytokine-mediated cell death. However, the identification of the mitochondrial carriers involved in its transport in hepatocellular mitochondria remains unestablished. In this study, we show that the functional expression of the 2-oxoglutarate carrier from HepG2 cells in mitochondria from Xenopus laevis oocytes conferred a reduced glutathione (GSH) transport activity that was inhibited by phenylsuccinate, a specific inhibitor of the carrier.

Cholesterol impairs the adenine nucleotide translocator-mediated mitochondrial permeability transition through altered membrane fluidity.

Mitochondrial permeability transition (MPT) has been proposed to play a key role in cell death. Downstream MPT events include the release of apoptogenic factors that sets in motion the mitochondrial apoptosome leading to caspase activation. The current work examined the regulation of MPT by membrane fluidity modulated upon cholesterol enrichment.

Ganglioside GD3 sensitizes human hepatoma cells to cancer therapy.

Ganglioside GD3 (GD3) has emerged as a modulator of cell death pathways due to its ability to interact with mitochondria and disable survival pathways. Because NF-kappaB activation contributes to cancer therapy resistance, this study was undertaken to test whether GD3 modulates the response of human hepatoblastoma HepG2 cells to radio- and chemotherapy. NF-kappaB was activated in HepG2 cells shortly after therapeutic doses of ionizing radiation or daunorubicin treatment that translated into up-regulation of kappaB-dependent genes.

Divergent role of ceramide generated by exogenous sphingomyelinases on NF-kappa B activation and apoptosis in human colon HT-29 cells.

This study examined the role of ceramide generated by exogenous sphingomyelinases (SMases) on transcription nuclear factor-kappa B (NF-kappa B) activation and apoptosis in human colon epithelial HT-29 cells. Exogenous neutral (N) and acidic (A) SMase activated NF-kappa B with different kinetics, accounting for the diverse pattern of DNA binding of NF-kappa B complexes activated by tumor necrosis factor-alpha (TNF). NSMase activated predominantly RelA/p52 and RelA/p50 dimers within 30 min, while ASMase activated the p50/p50 homodimer by 20 h.