Functional interplay between RNA-binding protein HuR and microRNAs.

The mammalian RNA-binding protein (RBP) HuR associates with numerous mRNAs encoding proteins with roles in cell division, cell survival, immune response, and differentiation. HuR was known to stabilize many of these mRNAs and/or modulated their translation, but the molecular processes by which HuR affected the fate of target mRNAs was largely unknown. Evidence accumulated over the past five years has revealed that the influence of HuR on many bound transcripts depends on HuR's interplay with microRNAs which associate with the same mRNAs.

Growth inhibition by miR-519 via multiple p21-inducing pathways.

The microRNA miR-519 robustly inhibits cell proliferation, in turn triggering senescence and decreasing tumor growth. However, the molecular mediators of miR-519-elicited growth inhibition are unknown. Here, we systematically investigated the influence of miR-519 on gene expression profiles leading to growth cessation in HeLa human cervical carcinoma cells.

RNA-binding protein HuD controls insulin translation.

Although expression of the mammalian RNA-binding protein HuD was considered to be restricted to neurons, we report that HuD is present in pancreatic β cells, where its levels are controlled by the insulin receptor pathway. We found that HuD associated with a 22-nucleotide segment of the 5' untranslated region (UTR) of preproinsulin (Ins2) mRNA. Modulating HuD abundance did not alter Ins2 mRNA levels, but HuD overexpression decreased Ins2 mRNA translation and insulin production, and conversely, HuD silencing enhanced Ins2 mRNA translation and insulin production.

The oncogenic RNA-binding protein Musashi1 is regulated by HuR via mRNA translation and stability in glioblastoma cells.

Musashi1 (Msi1) is an evolutionarily conserved RNA-binding protein (RBP) that has profound implications in cellular processes such as stem cell maintenance, nervous system development, and tumorigenesis. Msi1 is highly expressed in many cancers, including glioblastoma, whereas in normal tissues, its expression is restricted to stem cells. Unfortunately, the factors that modulate Msi1 expression and trigger high levels in tumors are largely unknown.

Competitive regulation of nucleolin expression by HuR and miR-494.

The RNA-binding protein (RBP) nucleolin promotes the expression of several proliferative proteins. Nucleolin levels are high in cancer cells, but the mechanisms that control nucleolin expression are unknown. Here, we show that nucleolin abundance is controlled posttranscriptionally via factors that associate with its 3' untranslated region (3'UTR).

Translational control of TOP2A influences doxorubicin efficacy.

The cellular abundance of topoisomerase IIα (TOP2A) critically maintains DNA topology after replication and determines the efficacy of TOP2 inhibitors in chemotherapy. Here, we report that the RNA-binding protein HuR, commonly overexpressed in cancers, binds to the TOP2A 3'-untranslated region (3'UTR) and increases TOP2A translation. Reducing HuR levels triggered the recruitment of TOP2A transcripts to RNA-induced silencing complex (RISC) components and to cytoplasmic processing bodies.

Post-Transcriptional Control of the Hypoxic Response by RNA-Binding Proteins and MicroRNAs.

Mammalian gene expression patterns change profoundly in response to low oxygen levels. These changes in gene expression programs are strongly influenced by post-transcriptional mechanisms mediated by mRNA-binding factors: RNA-binding proteins (RBPs) and microRNAs (miRNAs). Here, we review the RBPs and miRNAs that modulate mRNA turnover and translation in response to hypoxic challenge.

Enhanced translation by Nucleolin via G-rich elements in coding and non-coding regions of target mRNAs.

RNA-binding proteins (RBPs) regulate gene expression at many post-transcriptional levels, including mRNA stability and translation. The RBP nucleolin, with four RNA-recognition motifs, has been implicated in cell proliferation, carcinogenesis and viral infection. However, the subset of nucleolin target mRNAs and the influence of nucleolin on their expression had not been studied at a transcriptome-wide level.

Global dissociation of HuR-mRNA complexes promotes cell survival after ionizing radiation.

Ionizing radiation (IR) triggers adaptive changes in gene expression. Here, we show that survival after IR strongly depends on the checkpoint kinase Chk2 acting upon its substrate HuR, an RNA-binding protein that stabilizes and/or modulates the translation of target mRNAs. Microarray analysis showed that in human HCT116 colorectal carcinoma cells (WT), IR-activated Chk2 triggered the dissociation of virtually all of HuR-bound mRNAs, since IR did not dissociate HuR target mRNAs in Chk2-null (CHK2-/-) HCT116 cells.

Brief naturalistic stress induces an alternative splice variant of SMG-1 lacking exon 63 in peripheral leukocytes.

Alternative splicing (AS) not only regulates the gene expression program in response to surrounding environment, but also produces protein isoforms with unique properties under stressful conditions. However, acute psychological stress-initiated AS events have not been documented in human studies. After assessments of changes in salivary cortisol levels and anxiety among 28 fourth-grade medical students 7 weeks prior to, 1 day before, immediately after, and 1 week after an examination for promotion, we selected 5 male students, who showed a typical stress response, and screened AS events in their circulating leukocytes using the GeneChip human exon 1.

High-throughput screening of brief naturalistic stress-responsive cytokines in university students taking examinations.

This study was designed to prospectively examine the impact of a brief naturalistic stressor (academic examination) on salivary/serum cortisol, measures of anxiety and depressive mood, and 50 circulating immune mediators assessed 7 days before, the first day of, and 2 days after the first term examination period (5 days) among 20 male and 6 female medical students (19.7+/-3.1 years, mean+/-SD).

Receptor activator of nuclear factor-kappaB ligand-induced mouse osteoclast differentiation is associated with switching between NADPH oxidase homologues.

Reactive oxygen species (ROS) have been suggested to regulate receptor activator of nuclear factor-kappaB ligand (RANKL)-stimulated osteoclast differentiation. Stimulation of wild-type mouse bone marrow monocyte/macrophage lineage (BMM) cells by RANKL down-regulated NADPH oxidase 2 (Nox2) mRNA expression by half. RANKL reciprocally increased Nox1 mRNA levels and newly induced Nox4 transcript expression.

NADPH oxidase-derived reactive oxygen species are essential for differentiation of a mouse macrophage cell line (RAW264.7) into osteoclasts.

Reactive oxygen species (ROS) derived from NADPH oxidase (Nox) homologues have been suggested to regulate osteoclast differentiation. However, no bone abnormalities have been documented in Nox1 deficient, Nox2 deficient, or Nox3 mutant mice. During receptor activator of nuclear factor-kappaB ligand (RANKL)-stimulated differentiation of a mouse macrophage cell line (RAW264.

Tumor necrosis factor alpha activates transcription of the NADPH oxidase organizer 1 (NOXO1) gene and upregulates superoxide production in colon epithelial cells.

NADPH oxidase 1 (Nox1) is a multicomponent enzyme consisting of p22(phox), Nox organizer 1 (NOXO1), Nox1 activator 1, and Rac1. Interleukin-1beta, flagellin, interferon-gamma, and tumor necrosis factor alpha (TNF-alpha) similarly induced Nox1 in a colon cancer cell line (T84), whereas only TNF-alpha fully induced NOXO1 and upregulated superoxide-producing activity by ninefold. This upregulation was canceled by knockdown of NOXO1 with small interfering RNAs.

Bezafibrate, a peroxisome proliferator-activated receptors agonist, decreases body temperature and enhances electroencephalogram delta-oscillation during sleep in mice.

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the nuclear receptor family. PPARs play a critical role in lipid and glucose metabolism. We examined whether chronic treatment with bezafibrate, a PPAR agonist, would alter sleep and body temperature (BT).

Nox enzymes and oxidative stress in the immunopathology of the gastrointestinal tract.

Chronic inflammation caused by Helicobacter pylori infection or inflammatory bowel disease (IBD) is closely linked to cancer development. Innate immune abnormalities and enhanced production of reactive oxygen species through a phagocyte NADPH oxidase (Nox2) are key issues in understanding the pathogenesis of inflammation-dependent carcinogenesis. Besides Nox2, functionally distinct homologues (Nox1, Nox3, Nox4, Nox5, Duox1, and Duox2) have been identified.

Evidence for cancer-associated expression of NADPH oxidase 1 (Nox1)-based oxidase system in the human stomach.

Helicobacter pylori infection has been suggested to stimulate expression of the NADPH oxidase 1 (Nox1)-based oxidase system in guinea pig gastric epithelium, whereas Nox1 mRNA expression has not yet been documented in the human stomach. PCR of human stomach cDNA libraries showed that Nox1 and Nox organizer 1 (NOXO1) messages were absent from normal stomachs, while they were specifically coexpressed in intestinal- and diffuse-type adenocarcinomas including signet-ring cell carcinoma. Immunohistochemistry showed that Nox1 and NOXO1 proteins were absent from chronic atrophic gastritis (15 cases), adenomas (4 cases), or surrounding tissues of adenocarcinomas (45 cases).

NADPH oxidases in the gastrointestinal tract: a potential role of Nox1 in innate immune response and carcinogenesis.

The gastrointestinal epithelium functions as physical and innate immune barriers against commensal or pathogenic microbes. NADPH oxidase 1 (Nox1) and dual oxidase 2 (Duox2), highly expressed in the colon, are suggested to play a potential role in host defense. Guinea-pig gastric pit cells and human colonic epithelial cells (T84 cells) express Nox1.

Gene expression profiling in peripheral blood leukocytes as a new approach for assessment of human stress response.

Stress is the coordinated physiological processes to maintain a dynamic equilibrium under stressful conditions. The equilibrium is threatened by certain physiological and psychological stressors. Stressors trigger physiological, behavioural, and metabolic responses that are aimed at reinstating homeostasis.

Interferon-gamma activates transcription of NADPH oxidase 1 gene and upregulates production of superoxide anion by human large intestinal epithelial cells.

NADPH oxidase 1 (Nox1), a homolog of gp91(phox), is dominantly expressed in large intestinal epithelium, and reactive oxygen species derived from Nox1 are suggested to serve a role in host defense. We report that interferon (IFN)-gamma, a crucial transactivator of the gp91(phox) gene, also stimulates expression of Nox1 mRNA and protein in large intestinal epithelium (T84 cells), leading to fourfold upregulation of superoxide anion (O(2)(-)) generation. Introduction of small interfering Nox1 RNA completely blocked this priming.

Hematopoietic cell transplantation ameliorates clinical phenotype and progression of the CNS pathology in the mouse model of late onset Krabbe disease.

Krabbe disease is a genetic demyelinating disease caused by a deficiency of galactosylceramidase. The majority of cases are of infantile onset with rapid clinical course. A rare late onset form with milder clinical symptoms also exists.

Mutation in saposin D domain of sphingolipid activator protein gene causes urinary system defects and cerebellar Purkinje cell degeneration with accumulation of hydroxy fatty acid-containing ceramide in mouse.

The sphingolipid activator proteins (saposins A, B, C and D) are small homologous glycoproteins that are encoded by a single gene in tandem within a large precursor protein (prosaposin) and are required for in vivo degradation of some sphingolipids with relatively short carbohydrate chains. Human patients with prosaposin or specific saposin B or C deficiency are known, and prosaposin- and saposin A-deficient mouse lines have been generated. Experimental evidence suggests that saposin D may be a lysosomal acid ceramidase activator.

Genetic background markedly influences vulnerability of the hippocampal neuronal organization in the "twitcher" mouse model of globoid cell leukodystrophy.

The twitcher mouse is well known as a naturally occurring authentic mouse model of human globoid cell leukodystrophy (GLD; Krabbe disease) due to genetic deficiency of lysosomal galactosylceramidase. The twitcher mice used most commonly are on the C57BL/6J background. We generated twitcher mice that were on the mixed background of C57BL/6J and 129SvEv, the standard strain for production of targeted mutations.