Pescadillo Interacts with the Cadmium Response Element of the Human Heme Oxygenase-1 Promoter in Renal Epithelial Cells

The functional role of Pescadillo ribosomal biogenesis factor 1 in cancer

Tumors are neogrowths formed by the growth of normal cells or tissues through complex mechanisms under the influence of many factors. The occurrence and development of tumors are affected by many factors. Pescadillo ribosomal biogenesis factor 1 (PES1) has been identified as a cancer-related gene. The study of these genes may open up new avenues for early diagnosis, treatment and prognosis of tumors. As a nucleolar protein and part of the Pes1/Bop1/WDR12 (PeBoW) complex, PES1 is involved in ribosome biogenesis and DNA replication. Many studies have shown that high expression of PES1 is often closely related to the occurrence, proliferation, invasion, metastasis, prognosis and sensitivity to chemotherapeutics of various human malignant tumors through a series of molecular mechanisms and signaling pathways. The molecules that regulate the expression of PES1 include microRNA (miRNA), circular RNA (circRNA), c-Jun, bromodomain-containing protein 4 (BRD4) and nucleolar phosphoprotein B23. However, the detailed pathogenic mechanisms of PES1 overexpression in human malignancies remains unclear. This article summarizes the role of PES1 in the carcinogenesis, prognosis and treatment of multiple tumors, and introduces the molecular mechanisms and signal transduction pathways related to PES1.

A novel transcription factor MRPS27 up-regulates the expression of sqr, a key gene of mitochondrial sulfide metabolism in echiuran worm Urechis unicinctus

Hydrogen sulfide is a natural, widely distributed, poisonous substance and sulfide: quinone oxidoreductase (SQR) is responsible for oxidizing hydrogen sulfide to less toxic sulfur compounds. The increase of SQR mRNA level is an important mechanism for organisms to adapt to hydrogen sulfide-rich environments. However, its transcriptional regulation mechanism is not very clear. In this study, a mitochondrial 28S ribosomal protein S27 (MRPS27), which has never been reported as a transcription factor, was screened by yeast one-hybrid experiment from the echiuran worm Urechis unicinctus, a benthic organism living in marine sediments. Western blotting indicated that UuMRPS27 contents increased significantly in the nuclear extract of hindgut under exposed to 150 μM sulfide. ChIP and EMSA assays demonstrated that UuMRPS27 did bind to the sqr proximal promoter, the key binding sequence was CTAGAG (+12 to +17 of the promoter) detected by DNase I footprinting assay as well as transient transfection experiments. Furthermore, UuMRPS27, as a transcription activator, exhibited the highest transcription activity compared with other reported sqr transcription factors. Our data revealed for the first time the role of MRPS27 acting as a transcription factor which expanded the understanding of sqr transcriptional regulation in sulfide metabolism mechanism.

The Wnt/β-Catenin Pathway is Activated as a Novel Nucleolar Stress Response

Ribosomes are mandatory for growth and survival. The complex process of ribosome biogenesis is located in nucleoli and requires action of the RNA polymerases I-III, together with a multitude of processing factors involved in rRNA cleavage and maturation. Impaired ribosome biogenesis and loss of nucleolar integrity triggers nucleolar stress, which classically stabilizes the tumor suppressor p53 and induces cell cycle arrest and apoptosis. Nucleolar stress is implemented in modern anti-cancer therapies, however, also emerges as contributor to diverse pathological conditions. These include ribosomopathies, such as the Shwachman Bodian Diamond Syndrome (SBDS), which are not only characterized by nucleolar stress, but paradoxically also increased cancer incidence. Wnt signaling is tightly coupled to cell proliferation and is constitutively activated in various tumor types. In addition, the Wnt/β-Catenin pathway regulates ribosome formation. Here, we demonstrate that induction of nucleolar stress by different strategies stimulates the Wnt/β-Catenin pathway. We show that depletion of the key ribosomopathy factor SBDS, or the nucleolar factors Nucleophosmin (NPM), Pescadillo 1 (PES1) or Peter Pan (PPAN) by si RNA-mediated knockdown or CRISPR/Cas9 strategy activates Wnt/β-Catenin signaling in a β-Catenin-dependent manner and stabilizes β-Catenin in human cancer cells. Moreover, triggering nucleolar stress by the chemotherapeutic agents Actinomycin D or the RNA polymerase I inhibitor CX-5461 stimulates expression of Wnt/β-Catenin targets, which is followed by the p53 target CDKN1A (p21). As PPAN expression is induced by Wnt/β-Catenin signaling, our data establish a novel feedback mechanism and reveal that nucleolar stress over-activates the Wnt/β-Catenin pathway, which most likely serves as compensatory mechanism to sustain ribosome biogenesis.

Wnt Signaling in Neural Crest Ontogenesis and Oncogenesis

Neural crest (NC) cells are a temporary population of multipotent stem cells that generate a diverse array of cell types, including craniofacial bone and cartilage, smooth muscle cells, melanocytes, and peripheral neurons and glia during embryonic development. Defective neural crest development can cause severe and common structural birth defects, such as craniofacial anomalies and congenital heart disease. In the early vertebrate embryos, NC cells emerge from the dorsal edge of the neural tube during neurulation and then migrate extensively throughout the anterior-posterior body axis to generate numerous derivatives. Wnt signaling plays essential roles in embryonic development and cancer. This review summarizes current understanding of Wnt signaling in NC cell induction, delamination, migration, multipotency, and fate determination, as well as in NC-derived cancers.

Effect of hemin, baicalein and heme oxygenase-1 (HO-1) enzyme activity inhibitors on Cd-induced accumulation of HO-1, HSPs and aggresome-like structures in Xenopus kidney epithelial cells

Cadmium is a highly toxic environmental pollutant that can cause many adverse effects including cancer, neurological disease and kidney damage. Aquatic amphibians are particularly susceptible to this toxicant as it was shown to cause developmental abnormalities and genotoxic effects. In mammalian cells, the accumulation of heme oxygenase-1 (HO-1), which catalyzes the breakdown of heme into CO, free iron and biliverdin, was reported to protect cells against potentially lethal concentrations of CdCl₂. In the present study, CdCl₂ treatment of A6 kidney epithelial cells, derived from the frog, Xenopus laevis, induced the accumulation of HO-1, heat shock protein 70 (HSP70) and HSP30 as well as an increase in the production of aggregated protein and aggresome-like structures. Treatment of cells with inhibitors of HO-1 enzyme activity, tin protoporphyrin (SnPP) and zinc protoporphyrin (ZnPP), enhanced CdCl₂-induced actin cytoskeletal disorganization and the accumulation of HO-1, HSP70, aggregated protein and aggresome-like structures. Treatment of cells with hemin and baicalein, which were previously shown to provide cytoprotection against various stresses, induced HO-1 accumulation in a concentration-dependent manner. Also, treatment of cells with hemin and baicalein suppressed CdCl₂-induced actin dysregulation and the accumulation of aggregated protein and aggresome-like structures. This cytoprotective effect was inhibited by SnPP. These results suggest that HO-1-mediated protection against CdCl₂ toxicity includes the maintenance of actin cytoskeletal and microtubular structure and the suppression of aggregated protein and aggresome-like structures.

Of Wnts and Ribosomes

Wnt proteins are secreted glycoproteins that activate different intracellular signal transduction pathways. They regulate cell proliferation and are required for proper embryonic development. Misregulation of Wnt signaling can result in various diseases including cancer. In most circumstances, cell growth is essential for cell division and thus cell proliferation. Therefore, several reports have highlighted the key role of Wnt proteins for cell growth. Ribosomes represent the cellular protein synthesis machinery and cells need to be equipped with an appropriate number of ribosomes to allow cell growth. Recent findings suggest a role for Wnt proteins in regulating ribosome biogenesis and we here summarize these findings representing a previously unknown function of Wnt proteins. Understanding this role of Wnt signaling might open new avenues to slow down proliferation by drugs for instance in cancer therapy.

Measuring in vivo responses to endogenous and exogenous oxidative stress using a novel haem oxygenase 1 reporter mouse

Key points

Haem oxygenase 1 (Hmox1) is a cytoprotective enzyme with anti‐inflammatory and anti‐oxidant properties that is induced in response to multiple noxious environmental stimuli and disease states.

Tools to enable its expression to be monitored in vivo have been unavailable until now.

In a new Hmox1 reporter model we provide high‐fidelity, single‐cell resolution blueprints for Hmox1 expression throughout the body of mice.

We show for the first time that Hmox1 is constitutively expressed at barrier tissues at the interface between the internal and external environments, and that it is highly induced in muscle cells during systemic inflammation.

These data suggest novel biological insights into the role of Hmox1 and pave the way for the use of the model to study the role of environmental stress in disease pathology.

Abstract

Hmox1 protein holds great promise as a biomarker of in vivo stress responses as it is highly induced in stressed or damaged cells. However, Hmox1 expression patterns have thus far only been available in simple model organisms with limited relevance to humans. We now report a new Hmox1 reporter line that makes it possible to obtain this information in mice, a premiere model system for studying human disease and toxicology. Using a state‐of‐the‐art strategy, we expressed multiple complementary reporter molecules from the murine Hmox1 locus, including firefly luciferase, to allow long‐term, non‐invasive imaging of Hmox1 expression, and β‐galactosidase for high‐resolution mapping of expression patterns post‐mortem. We validated the model by confirming the fidelity of reporter expression, and its responsiveness to oxidative and inflammatory stimuli. In addition to providing blueprints for Hmox1 expression in mice that provide novel biological insights, this work paves the way for the broad application of this model to establish cellular stresses induced by endogenous processes and those resulting from exposure to drugs and environmental agents. It will also enable studies on the role of oxidative stress in the pathogenesis of disease and its prevention.

Haem oxygenase 1 (Hmox1) is a cytoprotective enzyme with anti‐inflammatory and anti‐oxidant properties that is induced in response to multiple noxious environmental stimuli and disease states.

Tools to enable its expression to be monitored in vivo have been unavailable until now.

In a new Hmox1 reporter model we provide high‐fidelity, single‐cell resolution blueprints for Hmox1 expression throughout the body of mice.

We show for the first time that Hmox1 is constitutively expressed at barrier tissues at the interface between the internal and external environments, and that it is highly induced in muscle cells during systemic inflammation.

These data suggest novel biological insights into the role of Hmox1 and pave the way for the use of the model to study the role of environmental stress in disease pathology.

DEAD-box helicase DDX27 regulates 3' end formation of ribosomal 47S RNA and stably associates with the PeBoW-complex

PeBoW, a trimeric complex consisting of pescadillo (Pes1), block of proliferation (Bop1), and the WD repeat protein 12 (WDR12), is essential for processing and maturation of mammalian 5.8S and 28S ribosomal RNAs. Applying a mass spectrometric analysis, we identified the DEAD-box helicase DDX27 as stably associated factor of the PeBoW-complex. DDX27 interacts with the PeBoW-complex via an evolutionary conserved F×F motif in the N-terminal domain and is recruited to the nucleolus via its basic C-terminal domain. This recruitment is RNA-dependent and occurs independently of the PeBoW-complex. Interestingly, knockdown of DDX27, but not of Pes1, induces the accumulation of an extended form of the primary 47S rRNA. We conclude that DDX27 can interact specifically with the Pes1 and Bop1 but fulfils critical function(s) for proper 3' end formation of 47S rRNA independently of the PeBoW-complex.

Recovery of redox homeostasis altered by CuNPs in H4IIE liver cells does not reduce the cytotoxic effects of these NPs: an investigation using aryl hydrocarbon receptor (AhR) dependent antioxidant activity

The generation of reactive oxygen species (ROS) and consequent oxidative stress is regarded as a relevant mechanism for nanoparticle toxicity. In cells, the activation of the aryl hydrocarbon receptor (AhR) triggers a cascade of defence responses against oxidative stress. By increasing AhR dependent cellular anti-oxidant activity, we tested the extent to which the cytotoxic effect of copper nanoparticles (CuNPs) is governed by oxidative stress. H4IIE rat hepatoma cells were challenged with high ROS levels after exposure to CuNPs, while the AhR-induced cellular anti-oxidant defence was simultaneously activated by the AhR ligand beta-Naphthoflavone (ßNF). Activation of phase II detoxification enzymes (as glutathione-S-transferases, GSTs) and anti-oxidants (glutathione, GSH) led to a complete abrogation of CuNP-induced ROS production. However, a concurrent reduction in cytotoxicity was not detected, thereby indicating that CuNPs exert non-oxidative stress mediated cytotoxic effects. Transmission electron microscopy analysis pointed to a direct physical perturbation of cellular structures by CuNPs, thus contributing to their cytotoxicity. Our observations highlight that distinct mechanisms underlie the toxicity of ions and NPs and indicate that while ROS elicitation is CuNP-specific, the cytotoxic action of these particles may not be directly related to their pro-oxidative activity. These findings have important implications with respect to the oxidative stress paradigm used to explain NP toxicity.

Transcriptional regulation and functional involvement of the Arabidopsis pescadillo ortholog AtPES in root development

The Pescadillo gene is highly conserved from yeasts to human and has been shown to impact on both the cell cycle and on ribosome biogenesis. However, the biological function and transcriptional regulation of the plant orthologs remain unclear. In the present study, we have implemented a combination of molecular and genetic approaches, in order to characterize the Arabidopsis thaliana pescadillo ortholog (AtPES) and its role in root development. The RNAi transgenic lines displayed severely compromised meristem structures and a reduction of the primary root length of up to 70%. The correct pattern of the cell files is distorted, whereas in the root elongation and differentiation zone the epidermal and cortex cells appear abnormally enlarged. Yeast two hybrid and BiFC experiments confirmed that AtPES interacts physically with AtPEIP1 and AtPEIP2, the orthologs of the murine Bop1 and WDR12. Promoter deletion analysis revealed that AtPES expression depends on a number of transcription factor binding sites, with the TELO-box being a crucial site for regulating its accurate tissue-specific manifestation. Our results indicate that AtPES is firmly regulated at the transcriptional level and that the corresponding protein plays a role in root developmental processes.

Accumulation of heme oxygenase-1 (HSP32) in Xenopus laevis A6 kidney epithelial cells treated with sodium arsenite, cadmium chloride or proteasomal inhibitors

The present study examined the effect of sodium arsenite, cadmium chloride, heat shock and the proteasomal inhibitors MG132, withaferin A and celastrol on heme oxygenase-1 (HO-1; also known as HSP32) accumulation in Xenopus laevis A6 kidney epithelial cells. Immunoblot analysis revealed that HO-1 accumulation was not induced by heat shock but was enhanced by sodium arsenite and cadmium chloride in a dose- and time-dependent fashion. Immunocytochemistry revealed that these metals induced HO-1 accumulation in a granular pattern primarily in the cytoplasm. Additionally, in 20% of the cells arsenite induced the formation of large HO-1-containing perinuclear structures. In cells recovering from sodium arsenite or cadmium chloride treatment, HO-1 accumulation initially increased to a maximum at 12h followed by a 50% reduction at 48 h. This initial increase in HO-1 levels was likely the result of new synthesis as it was inhibited by cycloheximide. Interestingly, treatment of cells with a mild heat shock enhanced HO-1 accumulation induced by low concentrations of sodium arsenite and cadmium chloride. Finally, we determined that HO-1 accumulation was induced in A6 cells by the proteasomal inhibitors, MG132, withaferin A and celastrol. An examination of heavy metal and proteasomal inhibitor-induced HO-1 accumulation in amphibians is of importance given the presence of toxic heavy metals in aquatic habitats.

Cadmium

Cadmium is not an essential element for life. It is geologically marginal but anthropogenic activities have contributed significantly to its dispersion in the environment and to cadmium exposure of living species. The natural speciation of the divalent cation Cd2+ is dominated by its high propensity to bind to sulfur ligands, but Cd2+ may also occupy sites providing imidazole and carboxylate ligands. It binds to cell walls by passive adsorption (bio-sorption) and it may interact with surface receptors. Cellular uptake can occur by ion mimicry through a variety of transporters of essential divalent cations, but not always. Once inside cells, Cd2+ preferentially binds to thiol-rich molecules. It can accumulate in intracellular vesicles. It may also be transported over long distances within multicellular organisms and be trapped in locations devoid of efficient excretion systems. These locations include the renal cortex of animals and the leaves of hyper-accumulating plants. No specific regulatory mechanism monitors Cd2+ cellular concentrations. Thiol recruitment by cadmium is a major interference mechanism with many signalling pathways that rely on thiolate-disulfide equilibria and other redox-related processes. Cadmium thus compromises the antioxidant intracellular response that relies heavily on molecules with reactive thiolates. These biochemical features dominate cadmium toxicity, which is complex because of the diversity of the biological targets and the consequent pleiotropic effects. This chapter compares the cadmium-handling systems known throughout phylogeny and highlights the basic principles underlying the impact of cadmium in biology.

Identification of proteins associated with an IFNγ-responsive promoter by a retroviral expression system for enChIP using CRISPR

Isolation of specific genomic regions retaining molecular interactions is essential for comprehensive identification of molecules associated with the genomic regions. Recently, we developed the engineered DNA-binding molecule-mediated chromatin immunoprecipitation (enChIP) technology for purification of specific genomic regions. Here, we developed a retroviral expression system for enChIP using CRISPR. We showed that the target genomic locus can be purified with high efficiency by using this system. We also showed that contamination of potential off-target sites is negligible by using this system if the guide RNA (gRNA) for the target site has a sufficiently long unique sequence in its seed sequence. enChIP combined with stable isotope labeling using amino acids in cell culture (SILAC) analysis identified proteins whose association with the interferon (IFN) regulatory factor-1 (IRF-1) promoter region increases in response to IFNγ stimulation. The list of the associated proteins contained many novel proteins in the context of IFNγ-induced gene expression as well as proteins related to histone deacetylase complexes whose involvement has been suggested in IFNγ-mediated gene expression. Finally, we confirmed IFNγ-induced increased association of the identified proteins with the IRF-1 promoter by ChIP. Thus, our results showed that the retroviral enChIP system using CRISPR would be useful for biochemical analysis of genome functions including transcription and epigenetic regulation.

Pescadillo plays an essential role in plant cell growth and survival by modulating ribosome biogenesis

Pescadillo (PES) is involved in diverse cellular processes such as embryonic development, ribosomal biogenesis, cell proliferation, and gene transcription in yeast and metazoans. In this study, we characterized cellular functions of plant PES in Nicotiana benthamiana, Arabidopsis, and tobacco BY-2 cells. A GFP fusion protein of PES is predominantly localized in the nucleolus, where its localization requires the N-terminal domain of PES. Silencing of plant PES led to growth arrest and acute cell death. PES interacts with plant homologs of BOP1 and WDR12 in the nucleolus, which are also nucleolar proteins involved in ribosome biogenesis of yeast and mammals. PES, BOP1, and WDR12 cofractionated with ribosome subunits. Depletion of any of these proteins led to defective biogenesis of the 60S ribosome large subunits and disruption of nucleolar morphology. PES-deficient plant cells also exhibited delayed maturation of 25S ribosomal RNA and suppressed global translation. During mitosis in tobacco BY-2 cells, PES is associated with the mitotic microtubules, including spindles and phragmoplasts, and PES deficiency disrupted spindle organization and chromosome arrangement. Collectively, these results suggest that plant PES has an essential role in cell growth and survival through its regulation of ribosome biogenesis and mitotic progression.

Transcriptional regulation of PES1 expression by c-Jun in colon cancer

Pescadillo is a nucleolar protein that has been suggested to be involved in embryonic development and ribosome biogenesis. Deregulated expression of human pescadillo (PES1) was described in some tumors, but its precise roles in tumorigenesis remains unclear. In this study, we generated three monoclonal antibodies recognizing PES1 with high specificity and sensitivity, with which PES1 expression in human colon cancer was analyzed immunohistochemically. Out of 265 colon cancer tissues, 89 (33.6%) showed positive PES1 expression, which was significantly higher than in non-cancerous tissues (P<0.001). Silencing of PES1 in colon cancer cells resulted in decreased proliferation, reduced growth of xenografts, and cell cycle arrest in G1 phase, indicating PES1 functions as an oncogene. We then explored the mechanism by which PES1 expression is controlled in human colon cancers and demonstrated that c-Jun, but not JunB, JunD, c-Fos, or mutant c-Jun, positively regulated PES1 promoter transcription activity. In addition, we mapped −274/−264 region of PES1 promoter as the c-Jun binding sequence, which was validated by chromatin immunoprecipitation and electrophoretic mobility shift assays. Moreover, we demonstrated a positive correlation between c-Jun and PES1 expression in colon cancer cells and colon cancer tissues. Upstream of c-Jun, it was revealed that c-Jun NH2-terminal kinases (JNK) is essential for controlling PES1 expression. Our study, in the first place, uncovers the oncogenic role of PES1 in colon cancer and elucidates the molecular mechanism directing PES1 expression.

PES1 promotes breast cancer by differentially regulating ERα and ERβ

The initiation of breast cancer is associated with increased expression of tumor-promoting estrogen receptor α (ERα) protein and decreased expression of tumor-suppressive ERβ protein. However, the mechanism underlying this process is unknown. Here we show that PES1 (also known as Pescadillo), an estrogen-inducible protein that is overexpressed in breast cancer, can regulate the balance between ERα and ERβ. We found that PES1 modulated many estrogen-responsive genes by enhancing the transcriptional activity of ERα while inhibiting transcriptional activity of ERβ. Consistent with this regulation of ERα and ERβ transcriptional activity, PES1 increased the stability of the ERα protein and decreased that of ERβ through the ubiquitin-proteasome pathway, mediated by the carboxyl terminus of Hsc70-interacting protein (CHIP). Moreover, PES1 transformed normal human mammary epithelial cells and was required for estrogen-induced breast tumor growth in nude mice. Further analysis of clinical samples showed that expression of PES1 correlated positively with ERα expression and negatively with ERβ expression and predicted good clinical outcome in breast cancer. Our data demonstrate that PES1 contributes to breast tumor growth through regulating the balance between ERα and ERβ and may be a better target for the development of drugs that selectively regulate ERα and ERβ activities.

In vivo regulation of the heme oxygenase-1 gene in humanized transgenic mice

Heme oxygenase-1 (HO-1) catalyzes the rate-limiting step in heme degradation producing equimolar amounts of carbon monoxide, iron, and biliverdin. Induction of HO-1 is a beneficial response to tissue injury in diverse animal models of diseases including acute kidney injury. In vitro analysis has shown that the human HO-1 gene is transcriptionally regulated by changes in chromatin conformation but whether such control occurs in vivo is not known. To enable such analysis, we generated transgenic mice, harboring an 87-kb bacterial artificial chromosome expressing human HO-1 mRNA and protein and bred these mice with HO-1 knockout mice to generate humanized BAC transgenic mice. This successfully rescued the phenotype of the knockout mice including reduced birth rates, tissue iron overload, splenomegaly, anemia, leukocytosis, dendritic cell abnormalities and survival after acute kidney injury induced by rhabdomyolysis or cisplatin nephrotoxicity. Transcription factors such as USF1/2, JunB, Sp1, and CTCF were found to associate with regulatory regions of the human HO-1 gene in the kidney following rhabdomyolysis. Chromosome Conformation Capture and ChIP-loop assays confirmed this in the formation of chromatin looping in vivo. Thus, these bacterial artificial chromosome humanized HO-1 mice are a valuable model to study the human HO-1 gene providing insight to the in vivo architecture of the gene in acute kidney injury and other diseases.

Mutation of pescadillo disrupts oligodendrocyte formation in zebrafish

Background

In vertebrates, the myelin sheath is essential for efficient propagation of action potentials along the axon shaft. Oligodendrocytes are the cells of the central nervous system that create myelin sheaths. During embryogenesis, ventral neural tube precursors give rise to oligodendrocyte progenitor cells, which divide and migrate throughout the central nervous system. This study aimed to investigate mechanisms that regulate oligodendrocyte progenitor cell formation.

Methodology/Principal Findings

By conducting a mutagenesis screen in transgenic zebrafish, we identified a mutation, designated vu166, by an apparent reduction in the number of oligodendrocyte progenitor cells in the dorsal spinal cord. We subsequently determined that vu166 is an allele of pescadillo, a gene known to play a role in ribosome biogenesis and cell proliferation. We found that pescadillo function is required for both the proper number of oligodendrocyte progenitors to form, by regulating cell cycle progression, and for normal levels of myelin gene expression.

Conclusions/Significance

Our data provide evidence that neural precursors require pes function to progress through the cell cycle and produce oligodendrocyte progenitor cells and for oligodendrocyte differentiation.

Pescadillo homologue 1 and Peter Pan function during Xenopus laevis pronephros development

BACKGROUND INFORMATION

pes1 (pescadillo homologue 1) and ppan (Peter Pan) are multifunctional proteins involved in ribosome biogenesis, cell proliferation, apoptosis, cell migration and regulation of gene expression. Both proteins are required for early neural development in Xenopus laevis, as previously demonstrated.

RESULTS

We show that the expression of both genes in the developing pronephros depends on wnt4 and fzd3 (frizzled homologue 3) function. Loss of pes1 or ppan by MO (morpholino oligonucleotide)-based knockdown approaches resulted in strong malformations during pronephric tubule formation. Defects were already notable during specification of pronephric progenitor cells, as shown by lhx1 expression. Moreover, we demonstrated that Xenopus pes1 and ppan interact physically and functionally and that pes1 and ppan can cross-rescue the loss of function phenotype of one another. Interference with rRNA synthesis, however, did not result in a similar early pronephros phenotype.

CONCLUSION

These results demonstrate that pes1 and ppan are required for Xenopus pronephros development and indicate that their function in the pronephros is independent of their role in ribosome biosynthesis.

Regulation of tolerance of Chlamydomonas reinhardtii to heavy metal toxicity by heme oxygenase-1 and carbon monoxide

Investigation of heavy metal tolerance genes in green algae is of great importance because heavy metals have become one of the major contaminants in the aquatic ecosystem. In plants, accumulation of heavy metals modifies many aspects of cellular functions. However, the mechanism by which heavy metals exert detrimental effects is poorly understood. In this study, we identified a role for HO-1 (encoding heme oxygenase-1) in regulating the response of Chlamydomonas reinhardtii, a unicellular green alga, to mercury (Hg). Transgenic algae overexpressing HO-1 showed high tolerance to Hg exposure, with a 48.2% increase in cell number over the wild type, but accumulated less Hg. Physiological analysis revealed that expression of HO-1 suppressed the Hg-induced generation of reactive oxygen species. We further identified the effect of carbon monoxide (CO), a product of HO-1-mediated heme degradation, on growth and physiological parameters. Interestingly, administration of exogenous CO at non-toxic levels also conferred the tolerance of algae to Hg exposure. The CO-mediated alleviation of Hg toxicity was closely related to the lower accumulation of Hg and free radical species. These results indicate that functional identification of HO-1 is useful for molecular breeding designed to improve plant tolerance to heavy metals and reduce heavy metal accumulation in plant cells.

Effect of heme oxygenase–endogenous carbon monoxide on mortality during septic shock in rats

Aim

To investigate the effect of HO–CO on mortality during septic shock in rats.

Method

Eighty rats were randomly divided into group-control, group ZnPP-IX, group SS, and group LZ.

Results

Death was significantly lower in group SS than in group LZ (P < 0.05). The MAP was significantly higher in the group LZ than in the group SS (P < 0.05). ALT, AST, Cr and BUN, MDA, and the lung EB contents, were significantly lower in the group SS than that in the group LZ (all P < 0.05). And CO and SOD activities were significantly higher in group SS than that in the group LZ (all P < 0.05). HO-1 mRNA, and HO-1 protein were significantly lower in the group LZ than in the group SS (P < 0.05), whereas HO-2 mRNA, and HO-2 protein were not significantly different among four groups (all P > 0.05).

Conclusion

The increased oxidative stress and end-organ damage is related to mortality during septic shock; while the hypotension partly contributing to HO-1 protein and CO has no obvious relation with it.

NRF2 Oxidative Stress Induced by Heavy Metals is Cell Type Dependent

Exposure to metallic environmental toxicants has been demonstrated to induce a variety of oxidative stress responses in mammalian cells. The transcription factor Nrf2 is activated in response to oxidative stress and coordinates the expression of antioxidant gene products. In this study, we describe the development of an Nrf2-specific reporter gene assay that can be used to study the oxidative stress response in multiple cell types. Using five different cell lines, the Nrf2-activating potency of twenty metals was assessed across a range of concentrations. While ten of the metals tested (cadmium, cobalt, copper, gold, iron, lead, mercury, silver, sodium arsenite and zinc) stimulated Nrf2-dependent transcriptional activity in at least three of the engineered cell lines, only three (cadmium, copper and sodium arsenite) were active in all five cell lines. A comparison of metal-induced Nrf2 transcriptional activation revealed significant differences in the absolute magnitude of activation as well as the relative potencies between the cell lines tested. However, there was no direct correlation between activity and potency. Taken together, these results show that the capacity to stimulate Nrf2 activity and relative potencies of these test compounds are highly dependent on the cell type tested. Since oxidative stress is thought to be involved in the mode of action of many toxicological studies, this observation may inform the design of paradigms for toxicity testing for toxicant prioritization and characterization.

Down-regulation of pescadillo inhibits proliferation and tumorigenicity of breast cancer cells

Pescadillo, which has been found to be involved in the process of ribosomal biogenesis, has been demonstrated to play a role in embryonic development, DNA replication, and gene transcription. While deregulation of ribosomal biogenesis was also found to contribute to carcinogenesis, and proteins that regulate ribosomal biogenesis are commonly overexpressed in primary tumors, little is known about the clinical significance and biological function of pescadillo in human breast cancer. In the current study, we found that the expression of pescadillo was markedly up-regulated in human breast cancer cells and tissues at both mRNA and protein levels. Immunohistochemical analysis revealed that pescadillo expression in clinical stage I-IV primary breast cancer tissues was statistically significantly higher than that in normal breast tissues (P < 0.05). Furthermore, we demonstrated that knockdown pescadillo with RNAis inhibited cell proliferation and the colony-forming ability of the cells. Anchorage-independent growth ability assay indicated that ablation of pescadillo led to the reduction of breast cancer cells tumorigenicity in vitro. Moreover, depletion of endogenous pescadillo resulted in decreased expression of cell cycle protein cyclin D1 and up-regulation of cyclin-dependent kinase inhibitor p27(Kip1), as well as attenuated protein kinase B (Akt)/glycogen synthase kinase 3 beta (GSK-3beta) signaling. Taken together, our results suggest that pescadillo might play a role in promoting the proliferation and carcinogenesis of human breast cancer, and thereby might be a potential target for human breast cancer treatment.

B23 interacts with PES1 and is involved in nucleolar localization of PES1

PES1, the human homolog of zebrafish pescadillo, is a nucleolar protein that is essential for cell proliferation. We report herein that a nucleolar marker protein B23 physically interacts with PES1 and is involved in the nucleolar localization of PES1. In vivo interaction between B23 and PES1 was verified by co-immunoprecipitation of endogenous B23 and PES1 proteins, and they showed cellular co-localizations under both normal and actinomycin D-induced stress conditions. Furthermore, we mapped their interaction domains via in vitro pulldown assays. When B23 was knocked down by RNA interference, there appeared an increased nucleoplasmic distribution of PES1. Our results support a previous hypothesis that B23 might be a nucleolar hub protein for protein targeting to the nucleolus, and shed light on the nucleolar localization mechanism of PES1. The physical interaction between B23 and PES1 implies that they may participate in ribosome biogenesis in a protein complex.

Human haem oxygenase-1 induction by nitro-linoleic acid is mediated by cAMP, AP-1 and E-box response element interactions

Nitro-fatty acid products of oxidative inflammatory reactions mediate anti-inflammatory cell signalling responses. LNO2 (nitrolinoleic acid) induces expression of HO-1 (haem oxygenase-1), an enzyme that catabolizes haem into products exhibiting potent anti-inflammatory properties. In the present manuscript, the molecular mechanisms underlying HO-1 induction by LNO2 were examined in HAEC (human aortic endothelial cells), HEK-293 (human embryonic kidney 293) cells, and in transcription factor-deficient MEF (mouse embryonic fibroblasts). LNO2 induced HO-1 expression in Nrf2 [NF-E2 (nuclear factor-erythroid 2)-related factor 2]-deficient MEF and in HEK-293 cells transfected with Nrf2-specific shRNA (small-hairpin RNA), supporting the fact that LNO2-mediated HO-1 induction can be regulated by Nrf2-independent mechanisms. LNO2 activated expression of a -4.5 kb human HO-1 promoter construct, whereas a -4.0 kb construct with deletion of 500 bp from the 5' region was unresponsive. Site-directed mutagenesis of a CRE (cAMP-response element) or of a downstream NF-E2/AP-1 (activating protein-1) element, individually, within this 500 bp region modestly reduced activation of the HO-1 promoter by LNO2. Mutations of both the CRE and the NF-E2/AP-1 site also attenuated LNO2-mediated HO-1 promoter expression, whereas the addition of a third mutation in the proximal E-box sequence completely abolished LNO2-induced HO-1 expression. Chromatin immunoprecipitation assays confirmed CREB (CRE-binding protein)-1 binding to the CRE (located at -4.0 kb) and E-box regions (located at -44 bp) of the human HO-1 promoter. A 3C (Chromosome Conformation Capture) assay of intact cells showed LNO2-induced interactions between the CRE- and E-box- containing regions. These observations indicate that regulation of human HO-1 expression by LNO2 requires synergy between CRE, AP-1 and E-box sequences and involves the participation of CREB-1.

Effect of heme oxygenase-1 on the kidney during septic shock in rats

The aim of this study was to clarify the effect of heme oxygenase (HO)-1 on the kidney during septic shock in rats. Eighty healthy and clean Sprague-Dawley rats were randomly divided into 4 groups: control group (group C) , septic shock group (group SS) , lipopolysaccharide plus ZnPP-IX group (group LZ) , and ZnPP-IX (group Z) . The plasma levels of COHb, Cr, and BUN; the urine levels of gamma-GTP, alpha1-MG, RBP, and NAG; and MDA content, SOD activity; HO-1mRNA; HO-2mRNA; HO-1 protein; and HO-2 protein from kidney were measured. The plasma levels of Cr and BUN; the urine levels of gamma-GTP, alpha1-MG, RBP, and NAG; and MDA content from kidney in group SS were obviously higher than in group C and Z (both P < 0.05), respectively, but lower than in group LZ (both P < 0.05), respectively. In contrast, the plasma levels of COHb and SOD activity from kidney in group SS were obviously lower than those in group C and Z (both P < 0.05), respectively, but higher than in group LZ (both P < 0.05), respectively. The HO-1mRNA and HO-1 protein of nephridial tissue in group LZ were obviously higher than in group C and Z, respectively (both P < 0.05), but lower than in group SS, respectively (both P < 0.05). There were no significant differences of HO-2mRNA and HO-2 protein among these 4 groups (both P > 0.05). It is concluded that upregulation of the HO-1 protein might contribute to the protection of kidney during septic shock in rats.

Pescadillo is required for Xenopus laevis eye development and neural crest migration

Pescadillo is a multifunctional, nuclear protein involved in rRNA precursor processing, ribosomal assembly, and transcriptional regulation. Pescadillo has been assigned important functions in embryonic development and tumor formation. We previously identified pescadillo as a potential downstream target of non-canonical Wnt-4 signaling. Here we have investigated for the first time the function of the Xenopus laevis homolog of pescadillo during early embryogenesis on a molecular level. Loss of function analysis indicates that pescadillo is required for eye development and neural crest migration. BrdU incorporation and TUNEL assays indicate that a loss of pescadillo function affects proliferation and triggers apoptosis through a p53-mediated mechanism. Furthermore, pescadillo affects the expression of early eye-specific marker genes, likely independent of its function in regulating proliferation and apoptosis, and in addition migration of cranial neural crest cells. Our data indicate that pescadillo has multiple important functions during X. laevis development and that its function is highly conserved among different species.

Cadmium-responsive Element of the Human Heme Oxygenase-1 Gene Mediates Heat Shock Factor 1-dependent Transcriptional Activation

Transcription of a number of mammalian genes is activated by heavy metals, but mechanisms of signaling and transcriptional regulation are not well understood. From a comparison of heavy metal responses of several human genes, it was noted that the heme oxygenase-1 (HO-1) gene is quite similar in the spectrum of metal response and induction kinetics to the heat shock protein 70 (HSP70) gene, suggesting a common regulatory mechanism shared by these genes. The cadmium-responsive element (CdRE) known to be responsible for the metal regulation of ho-1 formed complexes with proteins from heavy metal-treated HeLa cells in an electrophoretic mobility shift assay (EMSA). These complexes were indistinguishable in mobility from those formed by the heat shock factor 1 (HSF1) and the heat shock element involved in hsp70 regulation, suggesting the involvement of HSF1 also in the CdRE complexes. Competitive EMSA and supershift analysis with an anti-HSF1 antibody revealed that HSF1 was in fact a component of the CdRE complexes. A fine analysis on the affinity of HSF1 to a series of mutant CdRE sequences showed that HSF1 recognizes a sequence motif TnCTAGA. Transient transfection analysis with overexpressed recombinant HSF1 demonstrated that CdRE has HSF1-dependent enhancer-like activity that requires direct binding of HSF1. In the absence of overexpressed HSF1, however, CdRE by itself was insufficient to mediate heavy metal-induced transcription, suggesting requirement of additional regulatory sequences. The finding that HSF1 is directly involved in the regulation of ho-1 with an anti-oxidative role revealed a new aspect of the biological defense mechanism.

Light chain 1 of microtubule-associated protein 1B can negatively regulate the action of Pes1

Pes1 was first identified as the locus affected in the zebrafish mutant pescadillo, which exhibits severe defects in gut and liver development. It has since been demonstrated that loss of Pes1 expression in mammals and yeast affects ribosome biogenesis, resulting in a block in cell proliferation. Pes1 contains a BRCA1 C-terminal domain, a structural motif that has been shown to facilitate protein-protein interactions, suggesting that Pes1 has binding partners. We used a yeast two-hybrid screen to identify putative interacting proteins. We found that light chain 1 of the microtubule-associated protein 1B (Mtap1b-LC1) could partner with Pes1, and deletion analyses revealed a specific interaction of Mtap1b-LC1 with the Pes1 BRCA1 C-terminal domain. We confirmed the integrity of the interaction between Pes1 and Mtap1b-LC1 by co-immunoprecipitation experiments. Protein localization studies in NIH3T3 cells revealed that exogenously expressed Pes1 was typically restricted to nuclei and nucleoli. However, exogenous Pes1 was found predominantly in the cytoplasm in cells that were forced to express Mtap1b-LC1. We also observed that the expression of endogenous Pes1 protein was significantly reduced or undetectable in nuclei when Mtap1b-LC1 was overexpressed, implying that a dynamic interaction exists between the two proteins and that Mtap1b-LC1 has the potential to negatively impact Pes1 function. Finally, we demonstrated that, as is the case when Pes1 expression is depleted by shRNA, overexpression of Mtap1b-LC1 resulted in diminished proliferation of NIH3T3 cells, suggesting that Mtap1b-LC1 has the potential to repress cell proliferation by modulating the nucleolar levels of Pes1.

The BRCT domain of mammalian Pes1 is crucial for nucleolar localization and rRNA processing

The nucleolar protein Pes1 interacts with Bop1 and WDR12 in a stable complex (PeBoW-complex) and its expression is tightly associated with cell proliferation. The yeast homologue Nop7p (Yph1p) functions in both, rRNA processing and cell cycle progression. The presence of a BRCT-domain (BRCA1 C-terminal) within Pes1 is quite unique for an rRNA processing factor, as this domain is normally found in factors involved in DNA-damage or repair pathways. Thus, the function of the BRCT-domain in Pes1 remains elusive. We established a conditional siRNA-based knock-down-knock-in system and analysed a panel of Pes1 truncation mutants for their functionality in ribosome synthesis in the absence of endogenous Pes1. Deletion of the BRCT-domain or single point mutations of highly conserved residues caused diffuse nucleoplasmic distribution and failure to replace endogenous Pes1 in rRNA processing. Further, the BRCT-mutants of Pes1 were less stable and not incorporated into the PeBoW-complex. Hence, the integrity of the BRCT-domain of Pes1 is crucial for nucleolar localization and its function in rRNA processing.