Role of pescadillo in the transformation and immortalization of mammalian cells

The BRCT Domain from the Homologue of the Oncogene PES1 in Leishmania major (LmjPES) Promotes Malignancy and Drug Resistance in Mammalian Cells

Around 15% of cancer cases are attributable to infectious agents. Epidemiological studies suggest that an association between leishmaniasis and cancer does exist. Recently, the homologue of PES1 in Leishmania major (LmjPES) was described to be involved in parasite infectivity. Mammalian PES1 protein has been implicated in cellular processes like cell cycle regulation. Its BRCT domain has been identified as a key factor in DNA damage-responsive checkpoints. This work aimed to elucidate the hypothetical oncogenic implication of BRCT domain from LmjPES in host cells. We generated a lentivirus carrying this BRCT domain sequence (lentiBRCT) and a lentivirus expressing the luciferase protein (lentiLuc), as control. Then, HEK293T and NIH/3T3 mammalian cells were infected with these lentiviruses. We observed that the expression of BRCT domain from LmjPES conferred to mammal cells in vitro a greater replication rate and higher survival. In in vivo experiments, we observed faster tumor growth in mice inoculated with lentiBRCT respect to lentiLuc HEK293T infected cells. Moreover, the lentiBRCT infected cells were less sensitive to the genotoxic drugs. Accordingly, gene expression profiling analysis revealed that BRCT domain from LmjPES protein altered the expression of proliferation- (DTX3L, CPA4, BHLHE41, BMP2, DHRS2, S100A1 and PARP9), survival- (BMP2 and CARD9) and chemoresistance-related genes (DPYD, Dok3, DTX3L, PARP9 and DHRS2). Altogether, our results reinforced the idea that in eukaryotes, horizontal gene transfer might be also achieved by parasitism like Leishmania infection driving therefore to some crucial biological changes such as proliferation and drug resistance.

PES1 promotes the occurrence and development of papillary thyroid cancer by upregulating the ERα/ERβ protein ratio

PES1, a BRCT domain-containing protein, has been shown to play a role in modulating the balance and ratio between ERα and ERβ protein, which is involved in the occurrence and development of breast and ovarian cancer. However, its role in connection with the balance and ratio between ERα and ERβ protein in papillary thyroid cancer (PTC) remains unclear. Here, we found that ERα and ERβ were co-expressed in human PTC tissues and cells. ERα promoted and ERβ inhibited the proliferation, invasion and migration of PTC cells. PES1 modulated the balance between ERα and ERβ by elevating the ERα protein level and simultaneously reducing the ERβ protein level, then upregulating the ERα/ERβ protein ratio and promoting the proliferation, invasion and migration of PTC cells. In PTC tissues, PES1 protein level was positively correlated with the ERα protein level and negatively correlated with the ERβ protein level. The PES1 and ERα protein levels were gradually increased and the ERβ protein level was decreased by degree in the occurrence and development of PTC. Increased PES1 and ERα protein levels and decreased ERβ protein level were correlated with the aggressive behaviors of PTC patients such as large tumor size, extrathyroidal extension (ETE), lymph node metastasis (LNM), high BRAFV600E expression and high TNM stage. It is suggested that PES1 promotes the occurrence and development of PTC by elevating the ERα protein level and reducing the ERβ protein level, and then upregulating the ERα/ERβ protein ratio.

SUMOylation of PES1 upregulates its stability and function via inhibiting its ubiquitination

PES1 is a component of the PeBoW complex, which is required for the maturation of 28S and 5.8S ribosomal RNAs, as well as for the formation of the 60S ribosome. Deregulation of ribosomal biogenesis can contribute to carcinogenesis. In this study, we showed that PES1 could be modified by the small ubiquitin-like modifier (SUMO) SUMO-1, SUMO-2 and SUMO-3, and SUMOylation of PES1 was stimulated by estrogen (E2). One major SUMOylation site (K517) was identified in the C-terminal Glu-rich domain of PES1. Substitution of K517 with arginine abolished the SUMOylation of PES1. SUMOylation also stabilized PES1 through inhibiting its ubiquitination. In addition, PES1 SUMOylation positively regulated the estrogen signaling pathway. SUMOylation enhanced the ability of PES1 to promote estrogen receptor α (ERα)-mediated transcription by increasing the stability of ERα, both in the presence and absence of E2. Moreover, SUMOylation of PES1 also increased the proportion of S-phase cells in the cell cycle and promoted the proliferation of breast cancer cells both in vitro and in vivo. These findings showed that posttranslational modification of PES1 by SUMOylation may serve as a key factor that regulates the function of PES1 in vivo.

Proteomic Profile of Mabuya sp. (Squamata: Scincidae) Ovary and Placenta During Gestation

Reptiles are one of the most diverse groups of vertebrates, providing an integrated system for comparative studies on metabolic, animal physiology, and developmental biology. However, the molecular data available are limited and only recently have started to call attention in the "omics" sciences. Mabuya sp. is a viviparous placentrotrophic skink with particular reproductive features, including microlecithal eggs, early luteolysis, prolonged gestation, and development of a highly specialized placenta. This placenta is responsible for respiratory exchange and the transference of all nutrients necessary for embryonic development. Our aim was to identify differentially expressed proteins in the ovary and placenta of Mabuya sp. during early, mid, and late gestation; their possible metabolic pathways; and biological processes. We carried out a comparative proteomic analysis during gestation in both tissues by sodium dodecyl sulfate polyacrylamide gel electrophoresis, two-dimensional gel electrophoresis, and matrix-assisted laser desorption/ionization. Differential protein expression in both tissues (Student's t-test P < 0.05) was related to several processes such as cell structure, cell movement, and energy. Proteins found in ovary are mainly associated with follicular development and its regulation. In the placenta, particularly during mid and late gestation, protein expression is involved in nutrient metabolism, transport, protein synthesis, and embryonic development. This work provides new insights about the proteins expressed and their physiological mechanisms in Mabuya sp. placenta and ovary during gestation.

Lovastatin, but not orlistat, reduces intestinal polyp volume in an ApcMin/+ mouse model

The statins, inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCoAR) and orlistat, an inhibitor of fatty acid synthase (FAS), inhibit tumor cell growth by restricting cholesterol and fatty acid synthesis, respectively. We previously demonstrated that an omega (ω)-3 polyunsaturated fatty acid (PUFA)- or olive oil-enriched diet reduced the polyp number and volume in ApcMin/+ mice. This phenomenon was associated with a significant inhibition of FAS and HMGCoAR, as well as an increase in the estrogen receptor (ER)β/α ratio. Herein, we evaluated the effect of lovastatin and orlistat on polyp development and ER expression in ApcMin/+ mice, in order to confirm previous data obtained with ω‑3-PUFAs and olive oil. As expected, the use of lovastatin and orlistat significantly reduced HMGCoAR and FAS enzymatic activities and gene expression in colonic tissues, but did not affect the number of intestinal polyps, while there was a statistically significant reduction in polyp volume only in the mouse group treated with lovastatin. In the mice receiving orlistat, we observed a significant increase in cell proliferation in the polyp tissue, as well as enhanced expression of ERα. Moreover, the overexpression of ERα was associated with a statistically significant increase in PES1, Shh and Gli1 protein levels, considered ERα-related molecular targets.

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.

Targeting PES1 for restoring the ERα/ERβ ratio in breast cancer

Alteration of the ERα/ERβ balance is a critical step in breast cancer development and progression, and selective restoration of the activity of estrogen receptors has been proposed as one of the major therapeutic approaches for breast cancer. In this issue of JCI, Cheng et al. show that, by differentially modulating the stability of ERα and ERβ, PES1 increases the ERα/ERβ ratio and triggers breast tumor growth. These findings highlight PES1 as a potential target for the treatment of breast cancer.

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.

The chromosome peripheral proteins play an active role in chromosome dynamics

The chromosome periphery is a chromosomal structure that covers the surface of mitotic chromosomes. The structure and function of the chromosome periphery has been poorly understood since its first description in 1882. It has, however, been proposed to be an insulator or barrier to protect chromosomes from subcellular substances and to act as a carrier of nuclear and nucleolar components to direct their equal distribution to daughter cells because most chromosome peripheral proteins (CPPs) are derived from the nucleolus or nucleus. Until now, more than 30 CPPs were identified in mammalians. Recent immunostaining analyses of CPPs have revealed that the chromosome periphery covers the centromeric region of mitotic chromosomes in addition to telomeres and regions between two sister chromatids. Knockdown analyses of CPPs using RNAi have revealed functions in chromosome dynamics, including cohesion of sister chromatids, kinetochore-microtubule attachments, spindle assembly and chromosome segregation. Because most CPPs are involved in various subcellular events in the nucleolus or nuclear at interphase, a temporal and spatial-specific knockdown method of CPPs in the chromosome periphery will be useful to understand the function of chromosome periphery in cell division.

The Trypanosoma brucei life cycle switch TbPTP1 is structurally conserved and dephosphorylates the nucleolar protein NOPP44/46

Trypanosoma brucei adapts to changing environments as it cycles through arrested and proliferating stages in the human and tsetse fly hosts. Changes in protein tyrosine phosphorylation of several proteins, including NOPP44/46, accompany T. brucei development. Moreover, inactivation of T. brucei protein-tyrosine phosphatase 1 (TbPTP1) triggers differentiation of bloodstream stumpy forms into tsetse procyclic forms through unknown downstream effects. Here, we link these events by showing that NOPP44/46 is a major substrate of TbPTP1. TbPTP1 substrate-trapping mutants selectively enrich NOPP44/46 from procyclic stage cell lysates, and TbPTP1 efficiently and selectively dephosphorylates NOPP44/46 in vitro. To provide insights into the mechanism of NOPP44/46 recognition, we determined the crystal structure of TbPTP1. The TbPTP1 structure, the first of a kinetoplastid protein-tyrosine phosphatase (PTP), emphasizes the conservation of the PTP fold, extending to one of the most diverged eukaryotes. The structure reveals surfaces that may mediate substrate specificity and affords a template for the design of selective inhibitors to interfere with T. brucei transmission.

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.

Glioma-like proliferation within tissues excised as tubers in patients with tuberous sclerosis complex

We describe diffuse glioma-like infiltrates in excised tubers in five out of forty Tuberous sclerosis complex (TSC) patients undergoing excision of a tuber at our institution within the last 10 years. All patients presented with refractory seizures. Resection specimens from four patients had the pathognomonic histologic features of neuroglial hamartomas (tubers) and in one case there was cortical microdysgenesis lacking cells typical of TSC. All lesions were associated with an infiltrate of atypical, mostly elongate, glioma-like small cells, which were immunoreactive for GFAP in three, and pS6 (a marker for activity of the mTOR pathway), in two cases. MAP-2 and CD34, were negative and MIB-1 (Ki67) immunostains ranged from <1-21%. Array-based comparative genomic hybridization revealed that these proliferative phenomena were associated with 21 different copy number aberrations in comparison with a tuber without atypical infiltrates. Postoperatively (follow-up period ranging from 8 to 34 months) none of the patients have any evidence of a glioma. We report that tubers resected for treatment of seizures are sometimes associated with glioma-like lesions, which are indistinguishable from infiltrating gliomas by morphology and immunohistochemistry. Genomic analysis with SNP arrays revealed copy number changes which may be associated with the pathogenesis of such infiltrates.

Inhibition of IGF receptor signaling and hepatoma cell growth by an antibody to ligand oligopeptide of receptor

Research on insulin-like growth factor (IGF) system have shown it to be potent mitogen for hepatoma cells and made it an attractive therapeutic target. But little strategy has been reported to date on targeting and sequestrating IGF against hepatoma. This study is based on the capability of ligand oligopeptide (LOP) to recognize IGF receptor with high efficiency, which is over-expressed on some hepatoma cells. We have been hypothesizing that antibody to LOP would mimic the extracellular ligand-binding domain of IGF receptor and inhibit receptor signaling and cell proliferation. Gene encoding for LOP [E5 (EPFRSPDLALETYG)] of IGF receptor was inserted into HBc carrier for expression in Escherichia coli. The monoclonal antibody (mAb) specific LOP potently inhibited signal transduction mediated by the IGF-IR interaction with IGF-I. Furthermore, it exhibited 47% inhibitory rate of soft agar colony formation and also induced apoptosis. These results indicate an anti-hepatoma potential of the mAb to an LOP of IGF receptor could block the activation of receptor and downstream signaling pathways, and suppress the biological effects mediated by receptor.

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.

The antibody preparation and expression of human Pescadillo

To explore the biological roles of human Pescadillo and investigate its potential effect on tumorigenesis, the cDNA of Pescadillo was fused with that of GST. After purification and elution, the purified GST-Pescadillo fusion protein was obtained, and the antibody against the fusion protein was generated. Endogenous Pescadillo protein was observed to be remarkably induced by estrogen. It was mainly distributed in the tissues such as breast, ovary and intestine, all of which contain proliferating cells, and was also detected in many cell lines of human cancer: renal carcinoma, hepatoma, ovarian cancer, colon carcinoma, and breast cancer. The expression level of Pescadillo was increased significantly in breast cancer tissues compared with their paired margin tissues. Taken together, these data suggest that Pescadillo may play important roles in the initiation and development of cancer and may be a potential target in cancer diagnosis and therapy.

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.

Contribution of the BOP1 gene, located on 8q24, to colorectal tumorigenesis

The most common form of genomic instability observed in colorectal cancer is chromosomal instability (CIN), whose molecular bases remain to be determined. We have previously demonstrated that inactivation in human cells of several components of the Pes1-Bop1 complex (BOP1, GRWD1, PES1, ORC6L, and RPL3), involved in ribosome biogenesis, altered chromosome segregation. To determine the contribution to colorectal tumorigenesis of somatic alterations of genes involved in ribosome biogenesis, we screened 56 primary colorectal cancers, using quantitative multiplex PCR of short fluorescent fragments, a sensitive method for the detection of gene dosage alterations. We found that dosage increase of the BOP1 gene was a frequent event, being detected in 39% of the tumors, and we show that it is associated with an increase of BOP1 mRNA. Scanning of 8q24, on which BOP1 is located, revealed that in colorectal cancers, gene dosage increase of BOP1 can be independent from that of MYC and was more frequent than that affecting MYC. Finally, transient overexpression of BOP1 in human cells increased the percentage of multipolar spindles. Together with our previous results, the present study strongly suggests that deregulation of the BOP1 pathway contributes to colorectal tumorigenesis.

Protein microarrays for the detection of biomarkers in head and neck squamous cell carcinomas

Protein microarrays are of increasing importance for high-throughput screening of fresh tissues. In our study, protein microarrays were generated by printing antibodies onto membranes to characterize protein profiles expressed by head and neck squamous cell carcinomas (HNSCCs). Cellular proteomes of 30 matched normal squamous epithelial cells and carcinoma specimens were analyzed after tissue microdissection using microarrays composed of 83 different antibodies. As controls, Western blot analysis and tissue microarrays (TMAs) containing 98 HNSCC specimens were used. Of the 83 proteins examined, 14 showed differential expression between HNSCCs and normal epithelium. The protein microarray approach revealed an upregulation of 8 proteins and a downregulation of 6 proteins. Bag-1, Cox-2, Hsp-70, Stat3, pescadillo, MMP-7 (matrilysin), IGF-2, and cyclin D1 were identified to be significantly upregulated, whereas suppressor of cytokine signaling 1, thrombospondin, TGF-beta1, Jun, Fos, and Fra-2 were downregulated. The differential expression of these proteins was confirmed using Western blot and TMA. Upon correlation of differentially regulated proteins with the clinicopathologic data of our patients, MMP-7 (matrilysin) was found to be associated with survival in univariate, but not multivariate, analysis. These data indicate that our protein arrays provide protein information in a systematic, reproducible, and also high-throughput fashion.

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

Renal tubular cells elicit adaptive responses following exposure to nephrotoxins, such as cadmium. One response is the up-regulation of the 32-kDa redox-sensitive protein, heme oxygenase-1. Exposure of renal proximal tubular epithelial cells to 10 mum cadmium demonstrated induction ( approximately 20-fold) of heme oxygenase-1 mRNA and protein. Using a 4.5-kb human heme oxygenase-1 promoter construct, the importance of a previously identified cadmium response element (TGCTAGAT) in HeLa cells was verified in renal epithelial cells. Specific protein-DNA interaction with this sequence was demonstrated using nuclear extracts from cadmium-treated cells. Yeast one-hybrid screen of a human kidney cDNA library resulted in the identification of pescadillo, a unique nucleolar, developmental protein, as an interacting protein with the cadmium response element and was confirmed by chromatin immunoprecipitation in vivo and gel shift assays with purified glutathione S-transferase-pescadillo protein in vitro. The specificity of the DNA-protein interaction was verified by the absence of a binding complex when the core sequence of the cadmium response element was mutated or deleted. In addition, B23/nucleophosmin, another nucleolar protein, did not interact with the cadmium response sequence. Overexpression of pescadillo resulted in increased activity of the 4.5-kb human heme oxygenase-1 promoter construct but failed to activate this construct when the cadmium response sequence was mutated. The findings demonstrate the important and previously unrecognized role of pescadillo as a DNA-binding protein interacting specifically with the cadmium response element of the human heme oxygenase-1 gene.

Dominant-negative Pes1 mutants inhibit ribosomal RNA processing and cell proliferation via incorporation into the PeBoW-complex

The nucleolar PeBoW-complex, consisting of Pes1, Bop1 and WDR12, is essential for cell proliferation and processing of ribosomal RNA in mammalian cells. Here we have analysed the physical and functional interactions of Pes1 deletion mutants with the PeBoW-complex. Pes1 mutants M1 and M5, with N- and C-terminal truncations, respectively, displayed a dominant-negative phenotype. Both mutants showed nucleolar localization, blocked processing of the 36S/32S precursors to mature 28S rRNA, inhibited cell proliferation, and induced high p53 levels in proliferating, but not in resting cells. Mutant M1 and M5 proteins associated with large pre-ribosomal complexes and co-immunoprecipitated Bop1 and WDR12 proteins indicating their proper incorporation into the PeBoW-complex. We conclude that the dominant-negative effect of the M1 and M5 mutants is mediated by the impaired function of the PeBoW-complex.

Human pescadillo induces large-scale chromatin unfolding

The human pescadillo gene encodes a protein with a BRCT domain. Pescadillo plays an important role in DNA synthesis, cell proliferation and transformation. Since BRCT domains have been shown to induce chromatin large-scale unfolding, we tested the role of Pescadillo in regulation of large-scale chromatin unfolding. To this end, we isolated the coding region of Pescadillo from human mammary MCF10A cells. Compared with the reported sequence, the isolated Pescadillo contains in-frame deletion from amino acid 580 to 582. Targeting the Pescadillo to an amplified, lac operator-containing chromosome region in the mammalian genome results in large-scale chromatin decondensation. This unfolding activity maps to the BRCT domain of Pescadillo. These data provide a new clue to understanding the vital role of Pescadillo.

The insulin-like growth factor-I receptor as a target for cancer therapy

This review examines the rationale for targeting the insulin-like growth factor (IGF)-I receptor in the therapy of human tumours and their metastases. The rationale is based on two crucial findings: 1) in experimental animals, normal cells are only partially affected by the deletion of the IGF-I receptor, whereas tumour cells undergo apoptosis when the IGF-I receptor is downregulated; and 2) cells with a deleted IGF-I receptor are refractory to transformation by viral and cellular oncogenes. This review focuses on the mechanisms underlying the experimental findings, and discusses the possibility of extrapolating the results obtained in animals to the cure of human tumours.

Mammalian WDR12 is a novel member of the Pes1-Bop1 complex and is required for ribosome biogenesis and cell proliferation

Target genes of the protooncogene c-myc are implicated in cell cycle and growth control, yet the linkage of both is still unexplored. Here, we show that the products of the nucleolar target genes Pes1 and Bop1 form a stable complex with a novel member, WDR12 (PeBoW complex). Endogenous WDR12, a WD40 repeat protein, is crucial for processing of the 32S precursor ribosomal RNA (rRNA) and cell proliferation. Further, a conditionally expressed dominant-negative mutant of WDR12 also blocks rRNA processing and induces a reversible cell cycle arrest. Mutant WDR12 triggers accumulation of p53 in a p19ARF-independent manner in proliferating cells but not in quiescent cells. Interestingly, a potential homologous complex of Pes1–Bop1–WDR12 in yeast (Nop7p–Erb1p–Ytm1p) is involved in the control of ribosome biogenesis and S phase entry. In conclusion, the integrity of the PeBoW complex is required for ribosome biogenesis and cell proliferation in mammalian cells.

Functional significance of type 1 insulin-like growth factor-mediated nuclear translocation of the insulin receptor substrate-1 and beta-catenin

Previous work has shown that the transcriptional regulator beta-catenin can translocate to the nuclei when cells are stimulated with the type 1 insulin-like growth factor (IGF-1). We show by immunocoprecipitation and by confocal microscopy that beta-catenin binds to and co-localizes with the insulin receptor substrate-1 (IRS-1), a docking protein for both the insulin and the IGF-1 receptors. IRS-1 is required for IGF-1-mediated nuclear translocation of beta-catenin, resulting in the activation of the beta-catenin target genes. IGF-1-mediated nuclear translocation of beta-catenin is facilitated by the nuclear translocation of IRS-1. Both IRS-1 and beta-catenin are recruited to the cyclin D1 promoter, an established target for beta-catenin, but only IRS-1 is recruited to the ribosomal DNA (rDNA) promoter. UBF proteins (known to interact with both IRS-1 and beta-catenin) are also detectable in the cyclin D1 and rDNA promoters. These results indicate that IRS-1 (activated by the IGF-1 receptor) is one of several proteins that regulate the subcellular localization and activity of beta-catenin. The ability of IRS-1 to localize to both RNA polymerase II (with beta-catenin) and RNA polymerase I-regulated promoters suggest an explanation for the effect of IRS-1 on both cell growth in size and cell proliferation. This possibility is supported by the demonstration that enforced nuclear localization of IRS-1 causes nuclear translocation of beta-catenin and transformation of normal mouse embryo fibroblasts (colony formation in soft agar).