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The hallmark of Nanos proteins is their typical (CCHC)2 zinc finger motif (zf-nanos). Animals have one to four nanos genes. For example, the fruit fly and demosponge have only one nanos gene, zebrafish and humans have three, and Fugu rubripes has four. Nanos genes are mainly known for their evolutionarily preserved role in germ cell survival and pluripotency. Nanos proteins have been reported to bind the C-terminal RNA-binding domain of Pumilio to form a post-transcriptional repressor complex. Several observations point to a link between the miRNA-mediated repression complex and the Nanos/Pumilio complex. Repression of the E2F3 oncogene product is, indeed, mediated by cooperation between the Nanos/Pumilio complex and miRNAs. Another important interaction partner of Nanos is the CCR4-NOT deadenylase complex. Besides the tissue-specific contribution of Nanos proteins to normal development, their ectopic expression has been observed in several cancer cell lines and various human cancers. An inverse correlation between the expression levels of human Nanos1 and Nanos3 and E-cadherin was observed in several cancer cell lines. Loss of E-cadherin, an important cell-cell adhesion protein, contributes to tumor invasion and metastasis. Overexpression of Nanos3 induces epithelial-mesenchymal transition in lung cancer cell lines partly by repressing E-cadherin. Other than some most interesting data from Nanos knockout mice, little is known about mammalian Nanos proteins, and further research is needed. In this review, we summarize the main roles of Nanos proteins and discuss the emerging concept of Nanos proteins as oncofetal antigens. [ABSTRACT FROM AUTHOR]

Background: NBPF1 (Neuroblastoma Breakpoint Family, member 1) was originally identified in a neuroblastoma patient on the basis of its disruption by a chromosomal translocation t(1;17)(p36.2;q11.2). Considering this genetic defect and the frequent genomic alterations of the NBPF1 locus in several cancer types, we hypothesized that NBPF1 is a tumor suppressor. Decreased expression of NBPF1 in neuroblastoma cell lines with loss of 1p36 heterozygosity and the marked decrease of anchorage-independent clonal growth of DLD1 colorectal carcinoma cells with induced NBPF1 expression further suggest that NBPF1 functions as tumor suppressor. However, little is known about the mechanisms involved. Methods: Expression of NBPF was analyzed in human skin and human cervix by immunohistochemistry. The effects of NBPF1 on the cell cycle were evaluated by flow cytometry. We investigated by real-time quantitative RT-PCR the expression profile of a panel of genes important in cell cycle regulation. Protein levels of CDKN1A-encoded p21CIP1/WAF1 were determined by western blotting and the importance of p53 was shown by immunofluorescence and by a loss-offunction approach. LC-MS/MS analysis was used to investigate the proteome of DLD1 colon cancer cells with induced NBPF1 expression. Possible biological interactions between the differentially regulated proteins were investigated with the Ingenuity Pathway Analysis tool. Results: We show that NBPF is expressed in the non-proliferative suprabasal layers of squamous stratified epithelia of human skin and cervix. Forced expression of NBPF1 in HEK293T cells resulted in a G1 cell cycle arrest that was accompanied by upregulation of the cyclin-dependent kinase inhibitor p21CIP1/WAF1 in a p53-dependent manner. Additionally, forced expression of NBPF1 in two p53-mutant neuroblastoma cell lines also resulted in a G1 cell cycle arrest and CDKN1A upregulation. However, CDKN1A upregulation by NBPF1 was not observed in the DLD1 cells, which demonstrates that NBPF1 exerts cell-specific effects. In addition, proteome analysis of NBPF1-overexpressing DLD1 cells identified 32 differentially expressed proteins, of which several are implicated in carcinogenesis. Conclusions: We demonstrated that NBPF1 exerts different tumor suppressive effects, depending on the cell line analyzed, and provide new clues into the molecular mechanism of the enigmatic NBPF proteins. [ABSTRACT FROM AUTHOR]

Kaiso is a BTB/POZ zinc finger protein known as a transcriptional repressor. It was originally identified through its in vitro association with the Armadillo protein p120ctn. Subcellular localization of Kaiso in cell lines and in normal and cancerous human tissues revealed that its expression is not restricted to the nucleus. In the present study we monitored Kaiso's subcellular localization during the cell cycle and found the following: (1) during interphase, Kaiso is located not only in the nucleus, but also on microtubular structures, including the centrosome; (2) at metaphase, it is present at the centrosomes and on the spindle microtubules; (3) during telophase, it accumulates at the midbody. We found that Kaiso is a genuine PCM component that belongs to a pericentrin molecular complex. We analyzed the functions of different domains of Kaiso by visualizing the subcellular distribution of GFP-tagged Kaiso fragments throughout the cell cycle. Our results indicate that two domains are responsible for targeting Kaiso to the centrosomes and microtubules. The first domain, designated SA1 for spindle-associated domain 1, is located in the center of the Kaiso protein and localizes at the spindle microtubules and centrosomes; the second domain, SA2, is an evolutionarily conserved domain situated just before the zinc finger domain and might be responsible for localizing Kaiso towards the centrosomal region. Constructs containing both SA domains and Kaiso's aminoterminal BTB/POZ domain triggered the formation of abnormal centrosomes. We also observed that overexpression of longer or full-length Kaiso constructs led to mitotic cell arrest and frequent cell death. Knockdown of Kaiso accelerated cell proliferation. Our data reveal a new target for Kaiso at the centrosomes and spindle microtubules during mitosis. They also strongly imply that Kaiso's function as a transcriptional regulator might be linked to the control of the cell cycle and to cell proliferation in cancer. [ABSTRACT FROM AUTHOR]

We recently established the critical role of the PTEN/MAGI-lb signalosome in stabilization of cell-cell contacts and suppression of invasiveness. The PTEN tumor suppressor is recruited to E-cadherin junctional complexes through the binding to the second PDZ domain of the MAGI-lb scaffolding molecule, whereas β-catenin interacts with the fifth PDZ domain. To identify additional effectors of this signalosome, we used yeast 2-hybrid screening. Among the clones identified, we focused on TRIP6, which belongs to the zyxin family of proteins. We demonstrated that TRIP6 interacted directly with MAGI-lb by binding to its fifth PDZ domain. Ectopic expression of TRIP6 induced invasiveness in the epithelial MDCK and MDCKts-src cells in a PI3-kinase- and a NF-κB-dependent manner and impaired cell-cell aggregation at least in part by uncoupling adherens junctional complexes from the cytoskeleton. The TRIP6Stop473 mutant, which lacks the PDZ binding motif, was still able to increase NF-κB and Akt activities but did not promote invasiveness or interfere with cell-cell aggregation. Intracellular delivery of competing peptides corresponding to TRIP6 or β-catenin C terminus restored invasive properties in MDCKts-src TRIP6Stop473 cells, highlighting the requirement of PDZ scaffolds in junctional complexes activity. TRIP6 overexpression in colon tumors suggest its critical role in cancer progression. [ABSTRACT FROM AUTHOR]

Abstract: During development and carcinogenesis, the gradient of different molecular factors, the availability of corresponding receptors and the interplay between different signalling cascades combine to orchestrate the different stages. A good understanding of both developmental processes and oncogenesis leads to new insights into normal and aberrant regulation, processes that share some mutual key players. In this review, we will focus on the Snail family of transcription factors. These proteins, which share an evolutionarily conserved role in invertebrates and vertebrates, are implicated in several developmental processes, but are involved in carcinogenesis as well. We will highlight the different signalling cascades leading to the expression of Snail and Slug and how these factors are regulated on the transcriptional level. Then we will focus on how these factors execute their functions by repression of the numerous target genes that have been described to date. [Copyright &y& Elsevier]

Abnormal expression of the αE-catenin protein, a component of the E-cadherin/catenin cell adhesion complex, is frequently observed in human cancer cells. An inverse correlation between αE-catenin expression and tumor malignancy can be of prognostic value. Mutations of the αE-catenin gene, CTNNA1, were described in several human cancer cell lines and were found to result in aberrant cell adhesion. We have developed a polymerase chain reaction/single-strand conformation polymorphism-based method for mutation analysis of this gene in human tumor DNA. This approach enabled us to identify several polymorphisms in a set of desmoid tumors, demonstrating that this method is suitable for αE-catenin mutational analysis. On the basis of our genomic characterization data, we found that the previously reported alternative splicing of the αE-catenin gene actually generates a frame-shift, resulting in a truncated αE-catenin protein. This finding is unlike the other α-catenin family members αN-catenin and vinculin, which show in-frame alternative inserts. Furthermore, real-time quantitative reverse transcriptase–PCR analysis did not reveal relevant expression levels of this alternatively spliced αE-catenin variant neither in any human tissue or cell line tested, nor at any mouse developmental stage tested. Thus, contrary to previous notions, alternative splicing with in-frame insertion nearby the C-terminal end of the protein is not a general feature for all members of the α-catenin/vinculin family. [Copyright &y& Elsevier]