Genetic alterations of the NRP/B gene are associated with human brain tumors

Targeting kelch-like (KLHL) proteins: achievements, challenges and perspectives

Kelch-like proteins (KLHLs) are a large family of BTB-containing proteins. KLHLs function as the substrate adaptor of Cullin 3-RING ligases (CRL3) to recognize substrates. KLHLs play pivotal roles in regulating various physiological and pathological processes by modulating the ubiquitination of their respective substrates. Mounting evidence indicates that mutations or abnormal expression of KLHLs are associated with various human diseases. Targeting KLHLs is a viable strategy for deciphering the KLHLs-related pathways and devising therapies for associated diseases. Here, we comprehensively review the known KLHLs inhibitors to date and the brilliant ideas underlying their development.

Regulation of Cell Proliferation and Nrf2-Mediated Antioxidant Defense: Conservation of Keap1 Cysteines and Nrf2 Binding Site in the Context of the Evolution of KLHL Family

Keap1 (Kelch-like ECH-associated protein 1) is one of the major negative regulators of the transcription factor Nrf2 (nuclear factor erythroid-2-related factor 2), which induces the expression of numerous proteins defending the cell against different stress conditions. Keap1 is generally negatively regulated by post-translational modification (mostly via its cysteine residues) and interaction with other proteins that compete with Nrf2 for binding. Cysteine residues in Keap1 have different effects on protein regulation, as basic residues (Lys, Arg, and His) in close proximity to them increase cysteine modification potential. In this paper, we present an evolutionary analysis of residues involved in both mechanisms of Keap1 regulation in the broader context of the KLHL protein family in vertebrates. We identified the typical domain structure of the KLHL protein family in several proteins outside of this family (namely in KBTBD proteins 2, 3, 4, 6, 7, 8, 12 and 14). We found several cysteines that are flanked by basic residues (namely, C14, C38, C151, C226, C241, C273, C288, C297, C319, and C613) and, therefore, may be considered more susceptible to regulatory modification. The Nrf2 binding site is completely conserved in Keap1 in vertebrates but is absent or located in nonaligned DA and BC loops of the Kelch domain within the KLHL family. The development of specific substrate binding regions could be an evolutionary factor of diversification in the KLHL protein family.

Upregulated ENC1 predicts unfavorable prognosis and correlates with immune infiltration in endometrial cancer

A better knowledge of the molecular process behind uterine corpus endometrial carcinoma (UCEC) is important for prognosis prediction and the development of innovative targeted gene therapies. The purpose of this research is to discover critical genes associated with UCEC. We analyzed the gene expression profiles of TCGA-UCEC and GSE17025, respectively, using Weighted Gene Co-expression Network Analysis (WGCNA) and differential gene expression analysis. From four sets of findings, a total of 95 overlapping genes were retrieved. On the 95 overlapping genes, KEGG pathway and GO enrichment analysis were conducted. Then, we mapped the PPI network of 95 overlapping genes using the STRING database. Twenty hub genes were evaluated using the Cytohubba plugin, including NR3C1, ATF3, KLF15, THRA, NR4A1, FOSB, PER3, HLF, NTRK3, EGR3, MAPK13, ARNTL2, PKM2, SCD, EIF5A, ADHFE1, RERGL, TUB, and ENC1. The expression levels of NR3C1, PKM2, and ENC1 were shown to be adversely linked with the survival time of UCEC patients using univariate Cox regression analysis and Kaplan-Meier survival calculation. ENC1 were also overexpressed in UCEC tumor tissues or cell lines, as shown by quantitative real-time PCR and Western blotting. Then we looked into it further and discovered that ENC1 expression was linked to tumor microenvironment and predicted various immunological checkpoints. In conclusion, our data indicate that ENC1 may be required for the development of UCEC and may serve as a future biomarker for diagnosis and therapy.

Cell marathon: long-distance cell migration and metastasis-associated gene analysis using a folding paper system

A high mortality rate was found in cancer patients with distant metastasis. Development of targeted drugs for effectively inhibiting cancer metastasis is the key for increasing therapeutic success. In the current study, a folding paper system was developed to mimic a tumor-vascular interface for the study of long-distance cell migration. Correlation between the cell migration distance and metastasis-associated gene was successfully analyzed by disassembling the stacked paper construct. The result revealed that the migration distance and number of migrated cells were highly correlated to cell characteristics. Moreover, immunocytochemistry was directly conducted on the paper layer to study the signaling pathway. Kelch-like and protein tyrosine phosphatase families were examined and the PTPN13 gene was shown to regulate long-distance cell migration. By analyzing the phosphorylated mTOR, the PTPN13 gene was further confirmed to be a tumor suppressor gene that inhibits long-distance cell migration. The folding paper system provides an alternative approach for long-distance cell migration. Metastasis-associated gene expression can be analyzed to potentially develop targeted drugs for cancer metastasis inhibition.

METRO: Multi-ancestry transcriptome-wide association studies for powerful gene-trait association detection

Integrative analysis of genome-wide association studies (GWASs) and gene expression studies in the form of a transcriptome-wide association study (TWAS) has the potential to better elucidate the molecular mechanisms underlying disease etiology. Here we present a method, METRO, that can leverage gene expression data collected from multiple genetic ancestries to enhance TWASs. METRO incorporates expression prediction models constructed in different genetic ancestries through a likelihood-based inference framework, producing calibrated p values with substantially improved TWAS power. We illustrate the benefits of METRO in both simulations and applications to seven complex traits and diseases obtained from four GWASs. These GWASs include two of primarily European ancestry (n = 188,577 and 339,226) and two of primarily African ancestry (n = 42,752 and 23,827). In the real data applications, we leverage gene expression data measured on 1,032 African Americans and 801 European Americans from the Genetic Epidemiology Network of Arteriopathy (GENOA) study to identify a substantially larger number of gene-trait associations as compared to existing TWAS approaches. The benefits of METRO are most prominent in applications to GWASs of African ancestry where the sample size is much smaller than GWASs of European ancestry and where a more powerful TWAS method is crucial. Among the identified associations are high-density lipoprotein-associated genes including PLTP and PPARG that are critical for maintaining lipid homeostasis and the type II diabetes-associated gene MAPT that supports microtubule-associated protein tau as a key component underlying impaired insulin secretion.

Low expression of ENC1 predicts a favorable prognosis in patients with ovarian cancer

Ectodermal-neural cortex 1 (ENC1) belongs to a member of the kelch family of genes. It is an actin-binding protein and plays a pivotal role in neuronal and adipocyte differentiation. Here, we found that lower expression of ENC1 in the ovarian cancer patients was associated with favorable prognosis. In addition, ENC1 was heterogeneously expressed in various ovarian cancer cells. The messenger RNA and protein expression levels of ENC1 in HO-8910PM and NIH:OVCAR-3 cells were obviously higher than that in the other types of ovarian cancer cells. Knockdown of ENC1 in HO-8910PM or NIH:OVCAR-3 cells could significantly increase the reactive oxygen species levels, resulting in inhibition of in vitro proliferation, migration, and invasion. Our findings suggest that decreasing expression of ENC1 may be a new approach that can be used for ovarian cancer treatment.

The novel fusion transcript NR5A2-KLHL29FT is generated by an insertion at the KLHL29 locus

BACKGROUND

Novel fusion transcripts (FTs) caused by chromosomal rearrangement are common factors in the development of cancers. In the current study, the authors used massively parallel RNA sequencing to identify new FTs in colon cancers.

METHODS

RNA sequencing (RNA-Seq) and TopHat-Fusion were used to identify new FTs in colon cancers. The authors then investigated whether the novel FT nuclear receptor subfamily 5, group A, member 2 (NR5A2)-Kelch-like family member 29 FT (KLHL29FT) was transcribed from a genomic chromosomal rearrangement. Next, the expression of NR5A2-KLHL29FT was measured by quantitative real-time polymerase chain reaction in colon cancers and matched corresponding normal epithelia.

RESULTS

The authors identified the FT NR5A2-KLHL29FT in normal and cancerous epithelia. While investigating this transcript, it was unexpectedly found that it was due to an uncharacterized polymorphic germline insertion of the NR5A2 sequence from chromosome 1 into the KLHL29 locus at chromosome 2, rather than a chromosomal rearrangement. This germline insertion, which occurred at a population frequency of 0.40, appeared to bear no relationship to cancer development. Moreover, expression of NR5A2-KLHL29FT was validated in RNA specimens from samples with insertions of NR5A2 at the KLHL29 gene locus, but not from samples without this insertion. It is interesting to note that NR5A2-KLH29FT expression levels were significantly lower in colon cancers than in matched normal colonic epithelia (P =.029), suggesting the potential participation of NR5A2-KLHL29FT in the origin or progression of this tumor type.

CONCLUSIONS

NR5A2-KLHL29FT was generated from a polymorphism insertion of the NR5A2 sequence into the KLHL29 locus. NR5A2-KLHL29FT may influence the origin or progression of colon cancer. Moreover, researchers should be aware that similar FTs may occur due to transchromosomal insertions that are not correctly annotated in genome databases, especially with current assembly algorithms. Cancer 2017;123:1507-1515. © 2017 American Cancer Society.

Ectodermal-Neural Cortex 1 Isoforms Have Contrasting Effects on MC3T3-E1 Osteoblast Mineralization and Gene Expression

The importance of Wnt pathway signaling in development of bone has been well established. Here we investigated the role of a known Wnt target, ENC1 (ectodermal-neural cortex 1; NRP/B), in osteoblast differentiation. Enc1 expression was detected in mouse osteoblasts, chondrocytes, and osteocytes by in situ hybridization, and osteoblastic expression was verified in differentiating primary cultures and MC3T3-E1 pre-osteoblast cells, with 57 kDa and 67 kDa ENC1 protein isoforms detected throughout differentiation. Induced knockdown of both ENC1 isoforms reduced alkaline phosphatase staining and virtually abolished MC3T3-E1 mineralization. At culture confluence, Alpl (alkaline phosphatase liver/bone/kidney) expression was markedly reduced compared with control cells, and there was significant and coordinated alteration of other genes involved in cellular phosphate biochemistry. In contrast, with 67 kDa-selective knockdown mineralized nodule formation was enhanced and there was a two-fold increase in Alpl expression at confluence. There was enhanced expression of Wnt/β-catenin target genes with knockdown of both isoforms at this time-point and a five-fold increase in Frzb (Frizzled related protein) with 67 kDa-selective knockdown at mineralization, indicating possible ENC1 interactions with Wnt signaling in osteoblasts. These results are the first to demonstrate a role for ENC1 in the control of osteoblast differentiation. Additionally, the contrasting mineralization phenotypes and transcriptional patterns seen with coordinate knockdown of both ENC1 isoforms vs selective knockdown of 67 kDa ENC1 suggest opposing roles for the isoforms in regulation of osteoblastic differentiation, through effects on Alpl expression and phosphate cellular biochemistry. This study is the first to report differential roles for the ENC1 isoforms in any cell lineage. J. Cell. Biochem. 118: 2141-2150, 2017. © 2016 Wiley Periodicals, Inc.

The novel fusion transcript NR5A2-KLHL29FT is generated by an insertion at the KLHL29 locus

BACKGROUND

Novel fusion transcripts (FTs) caused by chromosomal rearrangement are common factors in the development of cancers. In the current study, the authors used massively parallel RNA sequencing to identify new FTs in colon cancers.

METHODS

RNA sequencing (RNA-Seq) and TopHat-Fusion were used to identify new FTs in colon cancers. The authors then investigated whether the novel FT nuclear receptor subfamily 5, group A, member 2 (NR5A2)-Kelch-like family member 29 FT (KLHL29FT) was transcribed from a genomic chromosomal rearrangement. Next, the expression of NR5A2-KLHL29FT was measured by quantitative real-time polymerase chain reaction in colon cancers and matched corresponding normal epithelia.

RESULTS

The authors identified the FT NR5A2-KLHL29FT in normal and cancerous epithelia. While investigating this transcript, it was unexpectedly found that it was due to an uncharacterized polymorphic germline insertion of the NR5A2 sequence from chromosome 1 into the KLHL29 locus at chromosome 2, rather than a chromosomal rearrangement. This germline insertion, which occurred at a population frequency of 0.40, appeared to bear no relationship to cancer development. Moreover, expression of NR5A2-KLHL29FT was validated in RNA specimens from samples with insertions of NR5A2 at the KLHL29 gene locus, but not from samples without this insertion. It is interesting to note that NR5A2-KLH29FT expression levels were significantly lower in colon cancers than in matched normal colonic epithelia (P =.029), suggesting the potential participation of NR5A2-KLHL29FT in the origin or progression of this tumor type.

CONCLUSIONS

NR5A2-KLHL29FT was generated from a polymorphism insertion of the NR5A2 sequence into the KLHL29 locus. NR5A2-KLHL29FT may influence the origin or progression of colon cancer. Moreover, researchers should be aware that similar FTs may occur due to transchromosomal insertions that are not correctly annotated in genome databases, especially with current assembly algorithms. Cancer 2017;123:1507-1515. © 2017 American Cancer Society.

Neonatal ventral hippocampus lesion changes nuclear restricted protein/brain (NRP/B) expression in hippocampus, cortex and striatum in developmental periods of rats

Schizophrenia is conceptualized as a neurodevelopmental disorder in which developmental alterations in immature brain systems are not clear. Rats with neonatal ventral hippocampal lesions (NVHL) can exhibit schizophrenia-like behaviors, and these rats have been widely used to study the developmental mechanisms of schizophrenia. The nuclear restricted protein/brain (NRP/B) is a nuclear matrix protein that is critical for the normal development of the neuronal system. This study assessed the effect of NVHL induced by the administration of ibotenic acid on the protein expression of NRP/B in the hippocampus, cortex and striatum in pre- and post-pubertal rats. The expressions of NeuN in various developmental periods were assessed accordingly. Sprague-Dawley rat pups were administered ibotenic acid at postnatal day (PD) 7. Western blotting and an immunofluorescence staining analysis showed that the expression of NRP/B was significantly decreased in the hippocampus, cortex and striatum of the NVHL rats at PD14, 28 and 42. The expressions of NeuN were decreased accordingly. In vitro experiment showed the NRP/B knockdown can decrease the Tuj1 expression in cultured cortical neurons. The data suggest that NVHL induces a change in NRP/B expression that affects neurons in the developmental period.

The Nuclear Matrix Protein, NRP/B, Acts as a Transcriptional Repressor of E2F-mediated Transcriptional Activity

Background:

NRP/B, a family member of the BTB/Kelch repeat proteins, is implicated in neuronal and cancer development, as well as the regulation of oxidative stress responses in breast and brain cancer. Our previous studies indicate that the NRP/B-BTB/POZ domain is involved in the dimerization of NRP/B and in a complex formation with the tumor suppressor, retinoblastoma protein. Although much evidence supports the potential role of NRP/B as a tumor suppressor, the molecular mechanisms of NRP/B action on E2F transcription factors have not been elucidated.

Methods:

Three-dimensional modeling of NRP/B was used to generate point mutations in the BTB/Kelch domains. Tet-on inducible NRP/B expression was established. The NRP/B deficient breast cancer cell line, MDA-MB-231, was generated using lentiviral shNRP/B to evaluate the effect of NRP/B on cell proliferation, invasion and migration. Immunoprecipitation was performed to verify the interaction of NRP/B with E2F and histone deacetylase (HDAC-1), and the expression level of NRP/B protein was analyzed by Western blot analysis. Changes in cell cycle were determined by flow cytometry. Transcriptional activities of E2F transcription factors were measured by chloramphenicol acetyltransferase (CAT) activity.

Results:

Ectopic overexpression of NRP/B demonstrated that the NRP/B-BTB/POZ domain plays a critical role in E2F-mediated transcriptional activity. Point mutations within the BTB/POZ domain restored E2-promoter activity inhibited by NRP/B. Loss of NRP/B enhanced the proliferation and migration of breast cancer cells. Endogenous NRP/B interacted with E2F and HDAC1. Treatement with an HDAC inhibitor, trichostatin A (TSA), abolished the NRP/B-mediated suppression of E2-promoter activity. Gain or loss of NRP/B in HeLa cells confirmed the transcriptional repressive capability of NRP/B on the E2F target genes, Cyclin E and HsORC (Homo sapiens Origin Recognition Complex).

Conclusions:

The present study shows that NRP/B acts as a transcriptional repressor by interacting with the co-repressors, HDAC1, providing new insight into the molecular mechanisms of NRP/B on tumor suppression.

New strategies to inhibit KEAP1 and the Cul3-based E3 ubiquitin ligases

E3 ubiquitin ligases that direct substrate proteins to the ubiquitin-proteasome system are promising, though largely unexplored drug targets both because of their function and their remarkable specificity. CRLs [Cullin-RING (really interesting new gene) ligases] are the largest group of E3 ligases and function as modular multisubunit complexes constructed around a Cullin-family scaffold protein. The Cul3-based CRLs uniquely assemble with BTB (broad complex/tramtrack/bric-à-brac) proteins that also homodimerize and perform the role of both the Cullin adapter and the substrate-recognition component of the E3. The most prominent member is the BTB-BACK (BTB and C-terminal Kelch)-Kelch protein KEAP1 (Kelch-like ECH-associated protein 1), a master regulator of the oxidative stress response and a potential drug target for common conditions such as diabetes, Alzheimer's disease and Parkinson's disease. Structural characterization of BTB-Cul3 complexes has revealed a number of critical assembly mechanisms, including the binding of an N-terminal Cullin extension to a bihelical '3-box' at the C-terminus of the BTB domain. Improved understanding of the structure of these complexes should contribute significantly to the effort to develop novel therapeutics targeted to CRL3-regulated pathways.

Identification of a subtype-specific ENC1 gene related to invasiveness in human pituitary null cell adenoma and oncocytomas

Non-functioning pituitary adenomas (NFPAs) may be locally invasive. Surgery is a treatment option, but unlike the case for functional pituitary adenomas, there are almost no drug treatments available for NFPAs. Markers of invasiveness are needed to guide therapeutic decision-making and identify potential adjuvant drugs. Owing to the highly heterogeneous nature of NFPAs, little is known regarding the subtype-specific gene expression profiles associated with invasiveness. To identify important biomarkers of invasiveness, we selected 23 null cell adenomas and 20 oncocytomas. These tumors were classified as invasive or non-invasive adenomas based on magnetic resonance imaging, pathology slides and surgical findings. Firstly, we observed that there were significant differences in expression between invasive (n = 3) and non-invasive (n = 4) adenomas by gene expression microarray. A total of 1,188 genes were differentially expressed in the invasive and non-invasive adenomas. Among these 1,188 genes, 578 were upregulated and 610 were downregulated in invasive adenomas. Secondly, the expression of ENC1, which displayed the significant alterations, was further confirmed by qRT-PCR and Western blot analysis in all 43 tumor samples and three normal pituitary glands. Low levels of ENC1 were found in tumor samples, while high levels were detected in normal pituitary glands. Interestingly, the ENC1 expression level was low in invasive null cell adenomas compared with non-invasive adenomas, but this relationship was not observed in invasive oncocytomas. Immunohistochemistry also demonstrated that the staining of ENC1 was different between invasive and non-invasive null cell adenomas. In addition, bioinformatics studies, including gene ontology and protein interaction analyses, were also performed to better understand the critical role of ENC1 in the development and progression of null cell adenomas and oncocytomas. Consequently, ENC1 may be an important biomarker for null cell adenomas and oncocytomas, and it is specific to invasive null cell adenomas.

Kelch proteins: emerging roles in skeletal muscle development and diseases

Our understanding of genes that cause skeletal muscle disease has increased tremendously over the past three decades. Advances in approaches to genetics and genomics have aided in the identification of new pathogenic mechanisms in rare genetic disorders and have opened up new avenues for therapeutic interventions by identification of new molecular pathways in muscle disease. Recent studies have identified mutations of several Kelch proteins in skeletal muscle disorders. The Kelch superfamily is one of the largest evolutionary conserved gene families. The 66 known family members all possess a Kelch-repeat containing domain and are implicated in diverse biological functions. In skeletal muscle development, several Kelch family members regulate the processes of proliferation and/or differentiation resulting in normal functioning of mature muscles. Importantly, many Kelch proteins function as substrate-specific adaptors for Cullin E3 ubiquitin ligase (Cul3), a core component of the ubiquitin-proteasome system to regulate the protein turnover. This review discusses the emerging roles of Kelch proteins in skeletal muscle function and disease.

Identification and Expression Profiling of the BTB Domain-Containing Protein Gene Family in the Silkworm, Bombyx mori

The BTB domain is a conserved protein-protein interaction motif. In this study, we identified 56 BTB domain-containing protein genes in the silkworm, in addition to 46 in the honey bee, 55 in the red flour beetle, and 53 in the monarch butterfly. Silkworm BTB protein genes were classified into nine subfamilies according to their domain architecture, and most of them could be mapped on the different chromosomes. Phylogenetic analysis suggests that silkworm BTB protein genes may have undergone a duplication event in three subfamilies: BTB-BACK-Kelch, BTB-BACK-PHR, and BTB-FLYWCH. Comparative analysis demonstrated that the orthologs of each of 13 BTB protein genes present a rigorous orthologous relationship in the silkworm and other surveyed insects, indicating conserved functions of these genes during insect evolution. Furthermore, several silkworm BTB protein genes exhibited sex-specific expression in larval tissues or at different stages during metamorphosis. These findings not only contribute to a better understanding of the evolution of insect BTB protein gene families but also provide a basis for further investigation of the functions of BTB protein genes in the silkworm.

Update on the Kelch-like (KLHL) gene family

The Kelch-like (KLHL) gene family encodes a group of proteins that generally possess a BTB/POZ domain, a BACK domain, and five to six Kelch motifs. BTB domains facilitate protein binding and dimerization. The BACK domain has no known function yet is of functional importance since mutations in this domain are associated with disease. Kelch domains form a tertiary structure of β-propellers that have a role in extracellular functions, morphology, and binding to other proteins. Presently, 42 KLHL genes have been classified by the HUGO Gene Nomenclature Committee (HGNC), and they are found across multiple human chromosomes. The KLHL family is conserved throughout evolution. Phylogenetic analysis of KLHL family members suggests that it can be subdivided into three subgroups with KLHL11 as the oldest member and KLHL9 as the youngest. Several KLHL proteins bind to the E3 ligase cullin 3 and are known to be involved in ubiquitination. KLHL genes are responsible for several Mendelian diseases and have been associated with cancer. Further investigation of this family of proteins will likely provide valuable insights into basic biology and human disease.

Identification of a biomarker panel for colorectal cancer diagnosis

BACKGROUND

Malignancies arising in the large bowel cause the second largest number of deaths from cancer in the Western World. Despite progresses made during the last decades, colorectal cancer remains one of the most frequent and deadly neoplasias in the western countries.

METHODS

A genomic study of human colorectal cancer has been carried out on a total of 31 tumoral samples, corresponding to different stages of the disease, and 33 non-tumoral samples. The study was carried out by hybridisation of the tumour samples against a reference pool of non-tumoral samples using Agilent Human 1A 60-mer oligo microarrays. The results obtained were validated by qRT-PCR. In the subsequent bioinformatics analysis, gene networks by means of Bayesian classifiers, variable selection and bootstrap resampling were built. The consensus among all the induced models produced a hierarchy of dependences and, thus, of variables.

RESULTS

After an exhaustive process of pre-processing to ensure data quality--lost values imputation, probes quality, data smoothing and intraclass variability filtering--the final dataset comprised a total of 8, 104 probes. Next, a supervised classification approach and data analysis was carried out to obtain the most relevant genes. Two of them are directly involved in cancer progression and in particular in colorectal cancer. Finally, a supervised classifier was induced to classify new unseen samples.

CONCLUSIONS

We have developed a tentative model for the diagnosis of colorectal cancer based on a biomarker panel. Our results indicate that the gene profile described herein can discriminate between non-cancerous and cancerous samples with 94.45% accuracy using different supervised classifiers (AUC values in the range of 0.997 and 0.955).

Nuclear matrix protein (NRP/B) modulates the nuclear factor (Erythroid-derived 2)-related 2 (NRF2)-dependent oxidative stress response

Reactive molecules have diverse effects on cells and contribute to several pathological conditions. Cells have evolved complex protective systems to neutralize these molecules and restore redox homeostasis. Previously, we showed that association of nuclear factor (NF)-erythroid-derived 2 (E2)-related factor 2 (NRF2) with the nuclear matrix protein NRP/B was essential for the transcriptional activity of NRF2 target genes in tumor cells. The present study demonstrates the molecular mechanism by which NRP/B, via NRF2, modulates the transcriptional activity of antioxidant response element (ARE)-driven genes. NRP/B is localized in the nucleus of primary brain tissue and human neuroblastoma (SH-SY5Y) cells. Treatment with hydrogen peroxide (H(2)O(2)) enhances the nuclear colocalization of NRF2 and NRP/B and induces heme oxygenase 1 (HO1). Treatment of NRP/B or NRF2 knockdowns with H(2)O(2) induced apoptosis. Co-expression of NRF2 with members of the Kelch protein family, NRP/B, MAYVEN, or MAYVEN-related protein 2 (MRP2), revealed that the NRF2-NRP/B complex is important for the transcriptional activity of ARE-driven genes HO1 and NAD(P)H:quinine oxidoreductase 1 (NQO1). NRP/B interaction with Nrf2 was mapped to NRF2 ECH homology 4 (Neh4)/Neh5 regions of NRF2. NRP/B mutations that resulted in low binding affinity to NRF2 were unable to activate NRF2-modulated transcriptional activity of the ARE-driven genes, HO1 and NQO1. Thus, the interaction of NRP/B with the Neh4/Neh5 domains of NRF2 is indispensable for activation of NRF2-mediated ARE-driven antioxidant and detoxifying genes that confer cellular defense against oxidative stress-induced damage.

Overexpression of Nrp/b (nuclear restrict protein in brain) suppresses the malignant phenotype in the C6/ST1 glioma cell line

Upon searching for glucocorticoid-regulated cDNA sequences associated with the transformed to normal phenotypic reversion of C6/ST1 rat glioma cells, we identified Nrp/b (nuclear restrict protein in brain) as a novel rat gene. Here we report on the identification and functional characterization of the complete sequence encoding the rat NRP/B protein. The cloned cDNA presented a 1767 nucleotides open-reading frame encoding a 589 amino acids residues sequence containing a BTB/POZ (broad complex Tramtrack bric-a-brac/Pox virus and zinc finger) domain in its N-terminal region and kelch motifs in its C-terminal region. Sequence analysis indicates that the rat Nrp/b displays a high level of identity with the equivalent gene orthologs from other organisms. Among rat tissues, Nrp/b expression is more pronounced in brain tissue. We show that overexpression of the Nrp/b cDNA in C6/ST1 cells suppresses anchorage independence in vitro and tumorigenicity in vivo, altering their malignant nature towards a more benign phenotype. Therefore, Nrp/b may be postulated as a novel tumor suppressor gene, with possible relevance for glioblastoma therapy.

Targeted ablation of PINCH1 and PINCH2 from murine myocardium results in dilated cardiomyopathy and early postnatal lethality

BACKGROUND

PINCH proteins are 5 LIM domain-only adaptor proteins that function as key components of the integrin signaling pathway and play crucial roles in multiple cellular processes. Two PINCH proteins, PINCH1 and PINCH2, have been described in mammals and share high homology. Both PINCH1 and PINCH2 are ubiquitously expressed in most tissues and organs, including myocardium. Cardiac-specific PINCH1 knockout or global PINCH2 knockout mice exhibit no basal cardiac phenotype, which may reflect a redundant role for these 2 PINCH proteins in myocardium. A potential role for PINCH proteins in myocardium remains unknown.

METHODS AND RESULTS

To define the role of PINCH in myocardium, we generated mice that were doubly homozygous null for PINCH1 and PINCH2 in myocardium. Resulting mutants were viable at birth but developed dilated cardiomyopathy and died of heart failure within 4 weeks. Mutant hearts exhibited disruptions of intercalated disks and costameres accompanied by fibrosis. Furthermore, multiple cell adhesion proteins exhibited reduced expression and were mislocalized. Mutant cardiomyocytes were significantly smaller and irregular in size. In addition, we observed that the absence of either PINCH1 or PINCH2 in myocardium leads to exacerbated cardiac injury and deterioration in cardiac function after myocardial infarction.

CONCLUSIONS

These results demonstrate essential roles for PINCHs in myocardial growth, maturation, remodeling, and function and highlight the importance of studying the role of PINCHs in human cardiac injury and cardiomyopathy.

Expression of ectodermal neural cortex 1 and its association with actin during the ovulatory process in the rat

Ectodermal neural cortex (ENC) 1, a member of the kelch family of genes, is an actin-binding protein and plays a pivotal role in neuronal and adipocyte differentiation. The present study was designed to examine the gonadotropin regulation and action of ENC1 during the ovulatory process in immature rats. The levels of ENC1 mRNA and protein were stimulated by LH/human chorionic gonadotropin (hCG) within 3 h both in vivo and in vitro. In situ hybridization analysis revealed that ENC1 mRNA was localized not only in theca/interstitial cells but also in granulosa cells of preovulatory follicles but not of growing follicles in pregnant mare's serum gonadotropin/hCG-treated ovaries. LH-induced ENC1 expression was suppressed by a high dose of protein kinase C inhibitor RO 31-8220 (10 microM) but not by low doses of RO 31-8220 (0.1-1.0 microM), suggesting the involvement of atypical protein kinase C. ENC1 was detected in both nucleus and cytoplasm that was increased by LH/hCG treatment. Both biochemical and morphological analysis revealed that LH/hCG treatment increased actin polymerization within 3 h in granulosa cells. Interestingly, ENC1 physically associated with actin and treatment with cytochalasin D, an actin-depolymerizing agent, abolished this association. Confocal microscopy further demonstrated the colocalization of ENC1 with filamentous actin (F-actin). The present study demonstrates that LH/hCG stimulates ENC1 expression and increases F-actin formation in granulosa cells. The present study further shows the physical association of ENC1 and F-actin, implicating the role of ENC1 in cytoskeletal reorganization during the differentiation of granulosa cells.

Expression of a BTB/POZ protein, NAC1, is essential for the proliferation of normal cyclic endometrial glandular cells and is up-regulated by estrogen

PURPOSE

The purpose of this study was to investigate the expression and localization of NAC1, a member of the BTB/POZ gene family in the human cyclic endometrium.

EXPERIMENTAL DESIGN

NAC1 expression in normal cyclic endometrium was assessed by immunohistochemistry, and data on clinical variables were collected by retrospective chart review. To elucidate the molecular mechanisms of NAC1 expression in the normal endometrium endometrial carcinoma cell lines (Ishikawa, HHUA; ER+, PR+) and primary cultured normal endometria were tested in a sex steroid induction assay and a NAC1 knockdown assay using siRNA.

RESULTS

Expression of NAC1 in glandular cells was significantly higher in the early and mid proliferative phases than in the other menstrual phases. Both NAC1 RNA and protein expression were up-regulated by treatment with 10 nmol/L 17beta-Estradiol (E2) in Ishikawa, HHUA and primary cultured normal endometrial cells. The estrogen receptor antagonist ICI 182,780 significantly attenuated E2-induced NAC1 expression. NAC1 gene knockdown inhibited cell growth and induced apoptosis in Ishikawa, HHUA, and normal endometria, all of which expressed NAC1. Furthermore, NAC1 siRNA significantly abrogated estrogen-driven cellular proliferation in Ishikawa, HHUA, and primary cultured normal endometrial cells, whereas the control siRNA had no effect on cell growth in any of these cells.

CONCLUSIONS

These findings suggest that NAC1 is functionally involved in E2-induced cell growth of the normal endometrial glandular cells. Because NAC1 is thought to have oncogenic potential, the current findings may provide new insight into the mechanism of estrogen induced endometrial carcinogenesis.

Ectodermal-neural cortex 1 down-regulates Nrf2 at the translational level

The transcription factor Nrf2 is the master regulator of a cellular defense mechanism against environmental insults. The Nrf2-mediated antioxidant response is accomplished by the transcription of a battery of genes that encode phase II detoxifying enzymes, xenobiotic transporters, and antioxidants. Coordinated expression of these genes is critical in protecting cells from toxic and carcinogenic insults and in maintaining cellular redox homeostasis. Activation of the Nrf2 pathway is primarily controlled by Kelch-like ECH-associated protein 1 (Keap1), which is a molecular switch that turns on or off the Nrf2 signaling pathway according to intracellular redox conditions. Here we report our finding of a novel Nrf2 suppressor ectodermal-neural cortex 1 (ENC1), which is a BTB-Kelch protein and belongs to the same family as Keap1. Transient expression of ENC1 reduced steady-state levels of Nrf2 and its downstream gene expression. Although ENC1 interacted with Keap1 indirectly, the ENC1-mediated down-regulation of Nrf2 was independent of Keap1. The negative effect of ENC1 on Nrf2 was not due to a change in the stability of Nrf2 because neither proteasomal nor lysosomal inhibitors had any effects. Overexpression of ENC1 did not result in a change in the level of Nrf2 mRNA, rather, it caused a decrease in the rate of Nrf2 protein synthesis. These results demonstrate that ENC1 functions as a negative regulator of Nrf2 through suppressing Nrf2 protein translation, which adds another level of complexity in controlling the Nrf2 signaling pathway.

NRP/B mutations impair Nrf2-dependent NQO1 induction in human primary brain tumors

Brain tumors are associated with genetic alterations of oncogenes and tumor suppressor genes. Accumulation of reactive oxygen species (ROS) in cells leads to oxidative stress-induced damage, resulting in tumorigenesis. Here, we showed that the nuclear matrix protein nuclear restricted protein in brain (NRP/B) was colocalized and interacted with NF-E2-related factor 2 (Nrf2). During oxidative stress response, NRP/B expression and its interaction with Nrf2 were upregulated in SH-SY5Y cells. Association of NRP/B with Nrf2 was crucial for NAD(P)H:quinone oxidoreductase 1 (NQO1) expression. NRP/B was localized predominantly in the nucleus of normal brain cells, whereas in primary brain tumors NRP/B was almost exclusively contained in the cytoplasm. In addition, unlike wild-type NRP/B, the expression of NRP/B mutants isolated from primary brain tumors was found in the cytoplasm, and these mutants failed to induce Nrf2-dependent NQO1 transcription. Thus, NRP/B mutations and their altered localization resulted in changes in NRP/B function and deregulation of Nrf2-dependent NQO1 activation in brain tumors. This study provides insights into the mechanism by which the NRP/B modulates Nrf2-dependent NQO1 induction in cellular protection against ROS in brain tumors.

A BTB/POZ gene, NAC-1, a tumor recurrence-associated gene, as a potential target for Taxol resistance in ovarian cancer

PURPOSE

We previously determined that NAC-1, a transcription factor and member of the BTB/POZ gene family, is associated with recurrent ovarian carcinomas. In the current study, we investigated further the relationship between NAC-1 expression and ovarian cancer.

EXPERIMENTAL DESIGN

NAC-1 expression was assessed by immunohistochemistry, and clinical variables were collected by retrospective chart review. SiRNA system and NAC-1 gene transfection were used to asses NAC-1 function in Taxol resistance in vivo.

RESULTS

Overexpression of NAC-1 correlated with shorter relapse-free survival in patients with advanced stage (stage III/IV) ovarian carcinoma treated with platinum and taxane chemotherapy. Furthermore, overexpression of NAC-1 in primary tumors predicted recurrence within 6 months after primary cytoreductive surgery followed by standard platinum and taxane chemotherapy. NAC-1 expression levels were measured and compared among the human ovarian cancer cell line (KF28), cisplatin-resistant cell line (KFr13) induced from KF28, and paclitaxel-resistant cell lines (KF28TX and KFr13TX) induced by exposing KF28 and KFr13 to dose-escalating paclitaxel. Overexpression of NAC-1 was observed in only the Taxol-resistant KF28TX and KFr13 TX cells but not in KF28 or cisplatin-resistant KFr13 cells. To confirm that NAC-1 expression was related to Taxol resistance, we used two independent but complementary approaches. NAC-1 gene knockdown in both KF28TX and KFr13TX rescued paclitaxel sensitivity. Additionally, engineered expression of NAC-1 in RK3E cells induced paclitaxel resistance.

CONCLUSIONS

These results suggest that NAC-1 regulates Taxol resistance in ovarian cancer and may provide an effective target for chemotherapeutic intervention in Taxol-resistant tumors.

The contribution of large genomic deletions at the CDKN2A locus to the burden of familial melanoma

Mutations in two genes encoding cell cycle regulatory proteins have been shown to cause familial cutaneous malignant melanoma (CMM). About 20% of melanoma-prone families bear a point mutation in the CDKN2A locus at 9p21, which encodes two unrelated proteins, p16^INK4a and p14^ARF. Rare mutations in CDK4 have also been linked to the disease. Although the CDKN2A gene has been shown to be the major melanoma predisposing gene, there remains a significant proportion of melanoma kindreds linked to 9p21 in which germline mutations of CDKN2A have not been identified through direct exon sequencing. The purpose of this study was to assess the contribution of large rearrangements in CDKN2A to the disease in melanoma-prone families using multiplex ligation-dependent probe amplification. We examined 214 patients from independent pedigrees with at least two CMM cases. All had been tested for CDKN2A and CDK4 point mutation, and 47 were found positive. Among the remaining 167 negative patients, one carried a novel genomic deletion of CDKN2A exon 2. Overall, genomic deletions represented 2.1% of total mutations in this series (1 of 48), confirming that they explain a very small proportion of CMM susceptibility. In addition, we excluded a new gene on 9p21, KLHL9, as being a major CMM gene.

The Nuclear Matrix Protein, NRP/B, Enhances Nrf2-Mediated Oxidative Stress Responses in Breast Cancer Cells

The transcription factor NF-E2-related factor 2 (Nrf2) translocates into the nucleus and activates phase II genes encoding detoxification enzymes and antioxidant proteins, resulting in the protection of cells from oxidative insults. However, the involvement of Nrf2-mediated oxidative stress responses in breast cancer cells is largely unknown. Notably, during our study of the Nrf2 pathway in breast cancer cells, we observed that the nuclear matrix protein NRP/B was expressed and colocalized with Nrf2 in these cells, suggesting that NRP/B is involved in Nrf2-mediated oxidative stress responses. The expression level of NRP/B was variable in different breast cancer cells and breast cancer tissues, and was found to be localized in the nucleus. NRP/B expression was increased after exposure to the oxidative stress agent, hydrogen peroxide (H(2)O(2)), particularly in the highly aggressive MDA-MB-231 breast cancer cells. Association of NRP/B with Nrf2 in vitro and in vivo was observed in MDA-MB-231 breast cancer cells, and this association was up-regulated upon exposure to H(2)O(2), but not to sodium nitroprusside, SIN-1, and DETA-NO. NRP/B also enhanced Nrf2-mediated NAD(P)H:quinine oxidoreductase 1 promoter activity. Thus, this study reveals that NRP/B enhances oxidative stress responses in breast cancer cells via the Nrf2 pathway, identifying a novel role of nuclear matrix protein(s) in oxidative stress responses.

Expression and clinical role of the bric-a-brac tramtrack broad complex/poxvirus and zinc protein NAC-1 in ovarian carcinoma effusions

We recently identified NAC-1, member of the bric-a-brac tramtrack broad complex/poxvirus and zinc domain family, as an overexpressed gene in ovarian serous carcinoma and found more frequent NAC-1 protein expression in recurrent compared to primary tumors. In the present study, we assessed the clinical significance of NAC-1 expression in ovarian carcinoma effusions. Formalin-fixed, paraffin-embedded sections from 176 effusions (137 peritoneal, 39 pleural) and 197 corresponding solid tumors (69 primary tumors, 128 solid metastases) were analyzed for NAC-1 expression using immunohistochemistry. Staining intensity and extent results were analyzed for possible association with clinicopathologic parameters and survival. Nuclear NAC-1 immunoreactivity was found in carcinoma cells in 98% of (173/176) effusions, 94% (65/69) of primary tumors, and 95% (121/128) of metastases. Staining intensity and extent were significantly higher in effusions compared with matched solid tumors (P = .002 for intensity, P = .003 for extent compared with primary tumors; P < .001 for both intensity and extent compared with metastases). Furthermore, NAC-1 expression intensity was significantly higher in specimens obtained after the administration of chemotherapy (P = .002) and correlated with shorter progression-free survival (PFS) in analysis of 62 patients with post-chemotherapy effusions (P = .039). International Federation of Gynecology and Obstetrics stage (IV versus III) was the only clinical parameter associated with PFS in this group (P = .004). In Cox analysis, only the International Federation of Gynecology and Obstetrics stage was an independent predictor of shorter PFS (P = .009). In conclusion, NAC-1 expression is higher in ovarian carcinoma cells in effusions compared with their solid tumor counterparts. NAC-1 is up-regulated in tumor cells after chemotherapy, suggesting a role for this protein in tumor progression and in the development of chemotherapy resistance in ovarian cancer.

Trishanku, a novel regulator of cell-type stability and morphogenesis in Dictyostelium discoideum

We have identified a novel gene, trishanku (triA), by random insertional mutagenesis of Dictyostelium discoideum. TriA is a Broad complex Tramtrack bric-a-brac domain-containing protein that is expressed strongly during the late G2 phase of cell cycle and in presumptive spore (prespore (psp)) cells. Disrupting triA destabilizes cell fate and reduces aggregate size; the fruiting body has a thick stalk, a lowered spore: stalk ratio, a sub-terminal spore mass and small, rounded spores. These changes revert when the wild-type triA gene is re-expressed under a constitutive or a psp-specific promoter. By using short- and long-lived reporter proteins, we show that in triA(-) slugs the prestalk (pst)/psp proportion is normal, but that there is inappropriate transdifferentiation between the two cell types. During culmination, regardless of their current fate, all cells with a history of pst gene expression contribute to the stalk, which could account for the altered cell-type proportion in the mutant.

KLHL1/MRP2 mediates neurite outgrowth in a glycogen synthase kinase 3beta-dependent manner

The actin-based cytoskeleton is essential for the generation and maintenance of cell polarity, cellular motility, and the formation of neural cell processes. MRP2 is an actin-binding protein of the kelch-related protein family. While MRP2 has been shown to be expressed specifically in brain, its function is still unknown. Here, we report that in neuronal growth factor (NGF)-induced PC12 cells, MRP2 was expressed along the neurite processes and colocalized with Talin at the growth cones. MRP2 mRNA and protein levels were up-regulated in PC12 cells following NGF stimulation. Moreover, treatment of PC12 cells with interfering RNAs for MRP2 and glycogen synthase kinase 3beta (GSK3beta) resulted in the inhibition of neurite outgrowth. A significant decrease in MRP2 expression levels was observed following GSK3beta inhibition, which was correlated with the inhibited neurite outgrowth, while GSK3beta overexpression was found to increase MRP2 expression levels. MRP2 interacted with GSK3beta through its NH2 terminus containing the BTB domain, and these molecules colocalized along neurite processes and growth cones in differentiated PC12 cells and rat primary hippocampal neurons. Additionally, increased associations of MRP2 with GSK3beta and MRP2 with actin were observed in the NGF-treated PC12 cells. Thus, this study provides, for the first time, insights into the involvement of MRP2 in neurite outgrowth, which occurs in a GSK3beta-dependent manner.

Detection of Autoantibodies to the BTB-kelch Protein KLHL7 in Cancer Sera

The aim of the study was to search for novel targets of autoantibodies in patients with paraneoplastic neurological syndromes (PNS). PNS are mediated by immune reactions against autoantigen(s) shared by the cancer cells and the nervous system. By serological screening of a rat cerebellum cDNA expression library using anti-Hu-positive sera from three patients with paraneoplastic encephalomyelitis (PEM), we identified an open reading frame encoding an isoform of the BTB-kelch protein KLHL7. Immunohistochemical studies demonstrated that the KLHL7 protein is expressed in the nuclei of neurones, but not in other tissues including various cancers. However, the KLHL7 protein was detected in the nuclei of cancer cell lines. Antibodies to KLHL7 were detected by an immunoprecipitation assay in sera from 12 of 254 (4.7%) patients with various cancers and 2 of 170 blood donors (1.2%). None of 50 sera from patients with multiple sclerosis were positive for KLHL7 antibodies. Sixteen patients with classical PNS and anti-Hu or anti-Yo antibodies were also negative for KLHL7 antibodies. Seven cancer patients with KLHL7 antibodies had various signs of neurological disease that could be related to cancer, whereas the remaining five seropositive cancer patients had no clinical signs of possible PNS. The present results indicate that KLHL7 antibodies are associated with various cancers, and in some patients also with neurological disease. Whether KLHL7 antibodies can be used as paraneoplastic markers for PNS remains to be determined.

Structure of the Keap1:Nrf2 interface provides mechanistic insight into Nrf2 signaling

Keap1 is a BTB-Kelch substrate adaptor protein that regulates steady-state levels of Nrf2, a bZIP transcription factor, in response to oxidative stress. We have determined the structure of the Kelch domain of Keap1 bound to a 16-mer peptide from Nrf2 containing a highly conserved DxETGE motif. The Nrf2 peptide contains two short antiparallel beta-strands connected by two overlapping type I beta-turns stabilized by the aspartate and threonine residues. The beta-turn region fits into a binding pocket on the top face of the Kelch domain and the glutamate residues form multiple hydrogen bonds with highly conserved residues in Keap1. Mutagenesis experiments confirmed the role of individual amino acids for binding of Nrf2 to Keap1 and for Keap1-mediated repression of Nrf2-dependent gene expression. Our results provide a detailed picture of how a BTB-Kelch substrate adaptor protein binds to its cognate substrate and will enable the rational design of novel chemopreventive agents.

Vaccinia virus kelch protein A55 is a 64 kDa intracellular factor that affects virus-induced cytopathic effect and the outcome of infection in a murine intradermal model

The vaccinia virus (VACV) protein A55 is a BTB/kelch protein with a broad-complex, tramtrack and bric-a-brac (BTB) domain in the N-terminal region and five kelch repeats in the C-terminal half. The BTB/kelch subgroup of the kelch superfamily of proteins has been associated with a wide variety of functions including regulation of the cytoskeleton. VACV contains three genes predicted to encode BTB/kelch proteins: A55R, F3L and C2L. The A55R gene product has been identified as an intracellular protein of 64 kDa that is expressed late in infection. A VACV strain lacking 93.6 % of the A55R open reading frame (vΔA55) was constructed and found to have an unaltered growth rate in vivo but a different plaque morphology and cytopathic effect, as well as reduced development of VACV-induced Ca2+-independent cell/extracellular matrix adhesion. In a murine intradermal model of VACV infection, a virus lacking the A55R gene induced larger lesions than wild-type and revertant control viruses.

The BTB domain of the nuclear matrix protein NRP/B is required for neurite outgrowth

The neuronal nuclear matrix protein, NRP/B, contains a BTB domain and kelch repeats and is expressed in primary neurons but not in primary glial cells. To examine the function of NRP/B in neurons, we analyzed the structure/function of the NRP/B-BTB domain and its role in neurite outgrowth. Based on three-dimensional modeling of NRP/B, we generated an NRP/B-BTB mutant containing three mutations in the conserved amino acids D47A, H60A and R61D that was termed BTB mutant A. BTB mutant A significantly reduced the dimerization of NRP/B compared to wild-type NRP/B. The NRP/B-BTB domain was required for nuclear localization and mediated the association of NRP/B with p110RB through the TR subdomain within the B pocket of p110RB. Overexpression of wild-type NRP/B and NRP/B-BTB domain significantly induced neurite outgrowth in PC12 cells and enhanced the G0-G1 cell population by ∼23% compared to the control cells, whereas NRP/B-BTB mutant A reduced neurite outgrowth by 70-80%, and inhibited NRP/B-p110RB association. Single cell microinjection of NRP/B-specific antibodies also blocked the neurite outgrowth of PC12 cells upon NGF stimulation. Interference of NRP/B expression by small interfering RNA (NRP/B-siRNA) inhibited neurite outgrowth and suppressed the NGF-induced outgrowth of neurites in PC12 cells. Additionally, p110RB phosphorylation at serine residue 795 was significantly reduced in PC12 cells treated with NRP/B siRNA compared to those treated with control GFP-siRNA, indicating that p110RB is a downstream target of NRP/B. Thus, the BTB domain of NRP/B regulates neurite outgrowth through its interaction with the TR subdomain within the B pocket of p110RB, and the conserved amino acids D47A, H60A and R61D within this domain of NRP/B are crucial residues for neurite extension in neuronal cells. These findings support a role for the BTB-domain of NRP/B as an important regulator of neuronal differentiation.

Ubiquitination of Keap1, a BTB-Kelch substrate adaptor protein for Cul3, targets Keap1 for degradation by a proteasome-independent pathway

Keap1 is a BTB-Kelch protein that functions as a substrate adaptor protein for a Cul3-dependent E3 ubiquitin ligase complex. Keap1 targets its substrate, the Nrf2 transcription factor, for ubiquitination and subsequent degradation by the 26 S proteasome. Inhibition of Keap1-dependent ubiquitination of Nrf2 increases steady-state levels of Nrf2 and enables activation of cytoprotective Nrf2-dependent genes. In this report, we demonstrate that Keap1 and three other BTB-Kelch proteins, including GAN1, ENC1, and Sarcosin, are ubiquitinated by a Cul3-dependent complex. Ubiquitination of Keap1 is markedly increased in cells exposed to quinone-induced oxidative stress, occurs in parallel with inhibition of Keap1-dependent ubiquitination of Nrf2, and results in decreased steady-state levels of Keap1, particularly in cells that are unable to synthesize glutathione. Degradation of Keap1 is independent of the 26 S proteasome, because inhibitors of the 26 S proteasome do not prevent loss of Keap1 following exposure of cells to quinone-induced oxidative stress. Our results suggest that a switch from substrate to substrate adaptor ubiquitination is a critical regulatory step that controls steady-state levels of both BTB-Kelch substrate adaptor proteins and their cognate substrates.

Mayven induces c-Jun expression and cyclin D1 activation in breast cancer cells

Mayven is a member of the kelch-related superfamily of proteins, characterized by a series of 'kelch' repeats at their carboxyl terminus and a BTB/POZ domain at their NH2-terminus. Little is known about the role of Mayven in cancer. Here, we report that Mayven expression was abundant and diffuse in primary human epithelial breast tumor cells as compared to normal breast epithelial cells, where Mayven was detected in the normal breast layer of the mammary ducts. Overexpression of Mayven resulted in an induction of c-Jun protein levels, as well as increased AP-1 (activating protein 1) transcriptional activity in MCF-7 and T47D breast cancer cells through its BTB/POZ domain. Furthermore, Mayven activated c-Jun N-terminal kinase in breast cancer cells. Mayven, through its BTB/POZ domain, induced cyclin D1 expression and cyclin D1 promoter activity and promoted cell cycle progression from the G1 to S phase. MCF-7 cells transduced with the recombinant retroviral sense Mayven (pMIG-W-Mayven) showed significant induction of c-Jun and cyclin D1 mRNA expression and activities as compared to the retroviral vector alone, while MCF-7 cells transduced by the recombinant retroviral antisense Mayven (pMIG-W-Mayven-AS) demonstrated a significant decrease in c-Jun and cyclin D1 expression and activities. Given the crucial functions of cyclin D1 and AP-1 signaling in oncogenesis, our results strongly suggest that overexpression of Mayven may promote tumor growth through c-Jun and cyclin D1.

Molecular changes in gliomas

PURPOSE OF REVIEW

Despite optimal clinical treatment, the prognosis for gliomas remains poor, and little progress has been observed during the last few years. Meanwhile, understanding of glioma oncogenesis has improved greatly. This review focuses on recent advances in molecular biology of glial tumors, with particular emphasis on lineage markers, genetic mechanisms underlying tumor progression, new diagnostic and prognostic markers, and potential therapeutic targets.

RECENT FINDINGS

The question of the cell of origin, illustrated by the evidence of tumor-derived multipotent progenitors, by the animal models of gliomas, and by lineage markers such as Olig1/2 markers, remains unsolved. Genotype/phenotype correlation studies have identified early and late genetic alterations related either to astrocytic or oligodendroglial phenotype. They complement the existing World Health Organization morphologic classification and provide additional prognostic markers such as 1p/19q deletion in oligodendrogliomas. Most of these genetic alterations result in the disruption of three main cellular systems: RB1, P53, and tyrosine kinase receptor pathways. New gene alterations have also been identified in glioma, promoting mitotic signal transduction, cell cycle regulation, apoptosis, angiogenesis, or invasion. Gene and protein profiling has been correlated with outcome.

SUMMARY

Management of gliomas, especially oligodendrogliomas with 1p19q deletion, benefits from advances in molecular genetics. A better understanding of the molecular pathogenesis and cellular lineage of gliomas will improve tumor classification and define more reliable prognostic markers. There is a hope that it will also lead to novel targets for therapy.