The Max network: coordinated transcriptional regulation of cell growth and proliferation.
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Four previously uncharacterized proteins (Tvp38, Tvp23, Tvp18 and Tvp15) were found in Tlg2-containing membrane by proteomic analysis of immunoisolated Golgi subcompartments of Saccharomyces cerevisiae (Inadome et al., Mol. Cell. Biol., 25 (2005) 7696-7710). Immunofluorescence double staining of HA-tagged Tvp proteins and myc-tagged tSNAREs supported that these proteins mainly localize in the Tlg2-containing compartments. Conserved sequences of Tvp38, Tvp23 and Tvp18 are found in higher eukaryotes, but these homologues have not been characterized yet. All Tvp proteins were nonessential for growth under laboratory conditions. Immunoprecipitation of Tvp proteins indicated that Tvp23, Tvp18 and Tvp15 are in an interactive network with Yip1-family proteins, Yip4 and Yip5. They may collectively assist in the effective maintenance/function of the late Golgi/endosomal compartments. Disruptions of tvp15 and tvp23 showed synthetic aggravation with ypt6 or ric1 null mutation. Processing of carboxypeptidase Y and alkaline phosphatase in tvp disruptants occurred as in the wild type.
Epithelial cells line the gastrointestinal mucosa and form an important barrier that protects the subepithelial tissue against a wide array of noxious substances, allergens, viruses and luminal microbial pathogens. Restoration of mucosal integrity following injury and various environmental stresses requires epithelial cell decisions that regulate signaling networks controlling gene expression, survival, migration and proliferation. Recently, it has been shown that polyamines play an important role in the regulation of cell-cell interactions and are critical for maintenance of intestinal epithelial integrity. Both the function of polyamines in expression of adherens junction proteins and their possible mechanisms, especially in implication of intracellular Ca2+ and c-Myc transcription factor, are the subject of this review article.
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Although great progress has been made at identifying and characterizing individual genes involved in cancer, less is known about how the combination of such genes collaborate to form tumors in humans. To this end, we sought to genetically recreate tumorigenesis in normal human cells using genes altered in human cancer. We now show that expression of mammalian proteins that inactivate the tumor suppressors Rb and p53 in conjunction with the oncoproteins Ras and Myc and the telomerase subunit hTERT is sufficient to drive a number of normal human somatic cells to a tumorigenic fate. This provides a blueprint of the events that lead to human cancer, allowing different cancers to be genetically modeled from normal human cells.
We previously demonstrated that truncated desmoplakin I (DP I) molecules containing the carboxyl terminus specifically coalign with and disrupt both keratin and vimentin intermediate filament (IF) networks when overexpressed in tissue culture cells (Stappenbeck, T. S., and K. J. Green. J. Cell Biol. 116:1197-1209). These experiments suggested that the DP carboxyl-terminal domain is involved either directly or indirectly in linking IF with the desmosome. Using a similar approach, we have now investigated the behavior of ectopically expressed full-length DP I in cultured cells. In addition, we have further dissected the functional sequences in the carboxyl terminus of DP I that facilitate the interaction with IF networks. Transient transfection of a clone encoding full-length DP I into COS-7 cells produced protein that appeared in some cells to associate with desmosomes and in others to coalign with and disrupt IF. Deletion of the carboxyl terminus from this clone resulted in protein that still appeared capable of associating with desmosomes but not interacting with IF networks. As the amino terminus appeared to be dispensable for IF interaction, we made finer deletions in the carboxyl terminus of DP based on blocks of sequence similarity with the related molecules bullous pemphigoid antigen and plectin. We found a sequence at the very carboxyl terminus of DP that was necessary for coalignment with and disruption of keratin IF but not vimentin IF. Furthermore, the coalignment of specific DP proteins along keratin IF but not vimentin IF was correlated with resistance to extraction by Triton. The striking uncoupling resulting from the deletion of specific DP sequences suggests that the carboxyl terminus of DP interacts differentially with keratin and vimentin IF networks.
Large-cell variants are uncommon in mantle cell lymphoma (MCL). Here we describe the pathologic and clinical findings in five patients with large-cell lymphoma related to MCL (L-MCL), and compare them to a group of classic small-cell MCL (s-MCL) cases. Histologically, the MC origin of the large cells was evinced by their association with a small mantle cell component in the same tissue, or their distribution in a classic mantle zone pattern, or their development in a patient with previous s-MCL. The large cells were either pleomorphic mantle cells (case 1) or transformed blast-like cells (case 2-5). The median nuclear diameter, median nuclear area and proliferation index of L-MCLs and s-MCLs, were statistically different. Immunophenotypic characterization of four specimens of L-MCL and 10 of s-MCLs with a large panel of antibodies showed the classic findings of MCL, i.e. the IgM+ D+/-, CD5+, CD10-, CD23- phenotype in all cases except two (one CD5- and one CD23+), and the association with a loose follicular dendritic cell network. Two of four L-MCLs and 5/10 s-MCLs demonstrated rearrangements of the bcl-1 gene by Southern blot or by polymerase chain reaction (PCR); 2/4 L-MCLs and 1/9 s-MCLs had p53 mutations on single-strand conformation polymorphism analysis; none of the 14 specimens showed rearrangement of bcl-2 by PCR or bcl-6 and c-myc by Southern blot. All patients with 'transformed' histology (versus 37% of all others) died of lymphoma; their survival (15-18 months; median 17) was much shorter than that of all the others (28-117+ months; median 43) (P=0.0035). All three patients with p53 anomalies, two of whom had tumours with transformed histology, died of their disease in a short time (15, 18 and 28 months). In contrast, the presence of bcl-1 rearrangements did not have prognostic implications. This study documents the existence of large-cell variants of MCL and the poor prognosis associated with the 'transformed' cytologic type and/or p53 abnormalities.
BACKGROUND: One of the most common and prevalent cancers is laryngeal squamous cell carcinoma (LSCC), which poses a great threat to the life and health of the patient. Nonetheless, it has been demonstrated that ubiquitination is crucial for the development and course of LSCC. Therefore, it is particularly important to identify biomarkers for ubiquitination-related genes (UbRGs) in LSCC. METHODS: Differentially expressed genes (DEGs) in the LSCC versus controls were obtained by differential expression analysis. Also, key modular genes associated with LSCC were obtained using weighted gene co-expression network analysis (WGCNA). Next, DEGs, key module genes, and UbRGs were taken to intersect to obtain candidate genes. And then machine algorithms were to screen potential biomarkers, further their diagnostic value were analyzed and validated. Then, therapeutic agents for biomarkers were predict. In addition, the regulatory networks of the biomarkers were mapped. The expression levels of biomarkers were detected in clinical samples using reverse transcription-quantitative PCR (RT-qPCR). RESULTS: A total of eight candidate genes were acquired by the overlap 1,911 DEGs, the key modular genes of WGCNA, and 1,393 UbRGs. A sum of four biomarkers (WDR54, KAT2B, NBEAL2 and LNX1) were identified by two machine learning, then these four biomarkers were validated in GSE127165 and the expression trend was consistent with TCGA-LSCC, they were recorded as biomarkers. Moreover, the accuracy of the biomarkers in predicting clinical aspects of LSCC was confirmed by the receiver operating characteristic (ROC) curves. Subsequently, cancers such as malignant neoplasms, colorectal cancers, tumors, and primary malignant neoplasms were significantly associated with the biomarkers, which further suggests that these four biomarkers were strongly associated with cancer. Meanwhile, the drugs garcinol, cocaine, and triazolam, among others, used for LSCC treatment were predicted. Finally, transcription factors (TFs) (BRD4, MYC, AR, and CTCF) were predicted to regulate the biomarkers. RT-qPCR assays illustrated that the expression trends of KAT2B, LNX1 and NBEAL2 remained consistent with the dataset. CONCLUSION: The identification of four biomarkers (WDR54, KAT2B, NBEAL2 and LNX1) associated with UbRGs could ultimately serve as a predictive clinical diagnosis of LSCC and provide insight into the molecular mechanisms of LSCC.
Microtubule-associated protein 1A (MAP1A) is a high-molecular-weight protein that is comprised of a heavy chain and a light chain (LC2) and is widely distributed along the microtubules in both mature neurons and glial cells. To illustrate the interaction among the MAP1A heavy chain, light chain, and microtubule, we prepared DNA constructs with Myc-, EGFP-, or DsRed-tags for full-length MAP1A DNA expressing whole MAP1A protein, two domains of MAP1A heavy chain, and light chain. Distribution patterns of various MAP1A domains as well as their interactions with microtubules were monitored in a non-neuronal COS7 and a neuronal Neuro2A cells. Our data revealed that a complete MAP1A protein, which contains both heavy chain and LC2, could be colocalized with microtubule networks not only in Neuro2A cells but also in transfected COS7 cells. Filamentous structures failed to be visualized along microtubules in COS7 cells transfected with MAP1A heavy chain or LC2 alone. Whereas, after introducing MAP1A heavy chain with LC2 into COS7 cells, both heavy chain and LC2 could be colocalized with microtubules. From our functional analysis, both MAP1A and its LC2 could protect microtubules against the challenge of nacodazol. Data collected from yeast two-hybrid assays of various MAP1A domains confirmed that the interaction of LC2 and NH2-terminal of MAP1A heavy chain is important for microtubule binding. From our analysis of MAP1A functional domains, we suggest that interactions between MAP1A heavy chain and LC2 are critical for the binding of microtubules.
Type 1 diabetes mellitus results from an autoimmune destruction of pancreatic beta-cells. Cytokines, such as interleukin-1 beta and interferon-gamma, are putative mediators of immune-induced beta-cell death and, under in vitro conditions, cause beta-cell apoptosis. We have recently shown that interleukin-1 beta + interferon-gamma modifies the expression of >200 genes in beta-cells. Several of these genes are putative targets for the transcription factor nuclear factor-kappa B (NF-kappa B), and in subsequent experiments we showed that NF-kappa B activation is mostly pro-apoptotic in beta-cells. To identify cytokine-induced and NF-kappa B-regulated genes in primary rat beta-cells, we presently combined two experimental approaches: 1) blocking of NF-kappa B activation in cytokine-exposed beta-cells by a recombinant adenovirus (AdI kappa B((SA)2)) containing an inhibitor of NF-kappa B alpha (I kappa Bac) super-repressor (S32A/S36A) and 2) study of gene expression by microarray analysis. We identified 66 cytokine-modified and NF-kappa B-regulated genes in beta-cells. Cytokine-induced NF-kappa B activation decreased Pdx-1 and increased c-Myc expression. This, together with NF-kappa B-dependent inhibition of Glut-2, pro-hormone convertase-1, and Isl-1 expression, probably contributes to the loss of differentiated beta-cell functions. NF-kappa B also regulates several genes encoding for chemokines and cytokines in beta-cells. The present data suggest that NF-kappa B is a key "switch regulator" of transcription factors and gene networks controlling cytokine-induced beta-cell dysfunction and death.
The Cu-ATPase ATP7A (MNK) is localized in the trans-Golgi network (TGN) and relocalizes in the plasma membrane via vesicle-mediated traffic following exposure of the cells to high concentrations of copper. Rab proteins are organelle-specific GTPases, markers of different endosomal compartments; their role has been recently reviewed (Trends Cell Biol. 11(2001) 487). In this article we analyze the endosomal pathway of trafficking of the MNK protein in stably transfected clones of CHO cells, expressing chimeric Rab5-myc or Rab7-myc proteins, markers of early or late endosome compartments, respectively. We demonstrate by immunofluorescence and confocal and electron microscopy techniques that the increase in the concentration of copper in the medium (189 microM) rapidly induces a redistribution of the MNK protein from early sorting endosomes, positive for Rab5-myc protein, to late endosomes, containing the Rab7-myc protein. Cell fractionation experiments confirm these results; i.e., the MNK protein is recruited to the endosomal fraction on copper stimulation and colocalizes with Rab5 and Rab7 proteins. These findings allow the first characterization of the vesicles involved in the intracellular routing of the MNK protein from the TGN to the plasma membrane, a key mechanism allowing appropriate efflux of copper in cells grown in high concentrations of the metal.
We used genetic strategies which have been proven valuable to decipher signaling pathways in comparatively simple organisms such as Drosophila and Caenorhabditis elegans, to dissect signaling network activated by tyrosine kinases in mammals. The strategy was developed further towards a generally applicable expression cloning system to identify signal transducers in tyrosine kinase pathways. This system is based on the ability of downstream acting genes to rescue the transformation phenotype of partial loss-of-function mutants of BCR-ABL which still retain tyrosine kinase activity. Using this strategy we have previously shown that overexpression of c-Myc and Cyclin D1 can rescue a signaling defective SH2 mutant of BCR-ABL for transformation. In an unbiased approach to identify new compensating genes, a cDNA library was introduced by retroviral infection into fibroblasts which express the BCR-ABL SH2 mutant. CDNA clones, capable of rescuing the SH2 mutant for transformation should result in colony formation in soft agar. A PCR approach was used to recover these compensating genes from the genomic DNA of the transformed fibroblasts. Sequencing analysis of the initial cDNAs identified three known genes, the adapter molecule Shc, the kinases SPRK and p38 MAPK. These genes have been found to interact functionally with BCR-ABL for fibroblast and hematopoietic cell transformation. Currently, we are constructing and screening new libraries to identify novel genes which complement the BCR-ABL SH2 mutant. Our results demonstrate that this cloning approach is an effective means of identifying and characterizing signaling molecules that function in specific signaling pathways. This in turn may identify specific targets for mechanism-based therapeutic intervention to block altered signaling.
Desmoplakins (DPs) I and II are two major related proteins located in the desmosomal plaque where they have been proposed to play a role in attaching intermediate filaments (IF) to the inner cell surface. The predicted amino acid sequence of DP was obtained by analysis of overlapping cDNA clones. Computer-aided analysis suggests that DPI will form a dumbbell-shaped homodimer, with a central alpha-helical coiled coil rod domain of 132 nm and two globular end domains. The DPII molecule is missing 599 residues from the central domain, resulting in a rod about one third the length of DPI. The carboxyl terminus comprises three subdomains each containing almost 5 repeats of a 38 residue repeating motif with a periodicity in acidic and basic residues similar to that found in the rod domain of IF proteins. This suggests a possible mechanism by which these proteins might interact. The amino terminus contains groups of heptad repeats that are predicted to form at least two major alpha-helical rich bundles. A series of c-myc-tagged mammalian expression vectors encoding specific predicted domains of DPI were transiently expressed in COS-7 cells. Light and electron microscopical observations revealed that DP polypeptides including the 90 kDa carboxyl terminal globular domain of DPI specifically colocalized with and ultimately resulted in the complete disruption of keratin and vimentin IF. This effect was specific for the carboxyl terminus, as the expression of the 95 kDa rod domain of DPI did not visibly alter IF networks.(ABSTRACT TRUNCATED AT 250 WORDS)
The concept that lymphomagenesis is a multistep process is now widely accepted. Various factors are involved in the development and malignant progression of B-cell lymphoproliferative disorders. The most frequently recognized alterations in these disorders are chromosomal translocations which lead to the activation of proto-oncogenes (c-myc) or genes encoding for proteins involved in the control of the cell cycle (cyclin D1), differentiation (bcl-6) and apoptosis (bcl-2). In addition, genetic changes that inactivate tumor suppressor genes (p53, Rb, p16) have recently been identified. Infectious agents may also play a role in lymphomagenesis either by directly driving B-cell proliferation (EBV) or by inducing a chronic antigenic stimulation (EBV, HCV, HBV, helicobacter pylori). Finally, several data indicate that local cytokine networks and, in particular, autocrine (IL-6, IL-10) and/or paracrine (IL-2, IL-4, IL-6) loops probably play a contributory role in the development and evolution of B-cell lymphoproliferation. In the last few years, the advent of molecular biology techniques has allowed important advances in the definition of the events involved i the earlier phases of lymphoma development. This has been made possible, in particular, by the study of a series of oligoclonal or monoclonal lymphoproliferative disorders characterized by an indolent or "smoldering" clinical course, such as follicular lymphoma and the lymphoproliferation associated with autoimmune diseases, which are at high risk of evolution to a highly malignant lymphoma. In nearly all of these conditions, the clonal B-cells responsible for the early stages of the disease are probably not fully transformed and retain various degrees of responsiveness to a wide variety of microenvironmental stimuli (antigen or autoantigen stimulation, interactions with "reactive" T lymphocytes, local cytokine networks). These latter in turn may induce the regression of pathological lesions, maintain the disease in an active state or contribute to the evolution towards an overtly malignant lymphoma. These findings open new avenues for the design of unconventional strategies of intervention aimed at preventing the malignant evolution of pre-lymphomatous lesions and controlling the clinical course of certain low-grade B-cell lymphomas.
This is a progress report of an attempt to deconstruct the signaling network underlying cell cycle control in the mouse Y1 adrenocortical cell line, aiming to uncover ACTH growth regulatory pathways. Y1 adrenocortical tumor cells possess amplified and overexpressed c-Ki-ras proto-oncogene. Despite this oncogenic lesion, Y1 cells retain tight regulatory mechanisms of cell cycle control typified by the sequential events comprising the mitogenic response triggered by FGF2 in G0/G1-arrested Y1 cells: 1) activation of ERK1/2 and PI3K, by 5 minutes; 2) induction of c-Fos and c-Myc proteins by 2 hours; 3) induction of cyclin D1 protein by 5 hours; 4) phosphorylation of Rb protein between 6 and 8 hours; 5) onset of DNA synthesis by 8-9 hours. In this cell line, ACTH-receptor (ACTH-R) activates contradictory pathways of growth regulation. First, ACTH coordinately induces fos and jun gene families via activation of both ERK1/2 and cAMP/PKA pathways, resembling a mitogen. Second, ACTH-R triggers cAMP/PKA-mediated antimitogenic mechanisms comprised of Akt/PKB dephosphorylation/deactivation, c-Myc protein degradation, and p27(Kip1) protein induction. Induction of cyclin D1 depends on activation of both ERK1/2 and PI3K, but is not affected by ACTH action. As a consequence, ACTH antagonizes FGF2 mitogenic activity but ectopic expression of the c-Myc protein (via MycER fusion protein) is sufficient to abrogate this ACTH antagonistic effect over FGF2 mitogenic activity. Ectopic expression of both c-Myc and cyclin D1 is not sufficient to drive G0/G1-arrested Y1 cells into S phase, but when the sustained expression of these two proteins is complemented by ACTH treatment it promotes G1 phase progression and DNA synthesis initiation. In conclusion, ACTH-receptor lacks signaling potential sufficient to initiate a mitogenic response in Y1 adrenocortical cells and, therefore, cannot substitute for bona fide mitogens like FGF2.
This article reviews recent results of studies aiming to elucidate modes of integrating signals initiated in ACTH receptors and FGF2 receptors, within the network system of signal transduction found in Y1 adrenocortical cells. These modes of signal integration should be central to the mechanisms underlying the regulation of the G0-->G1-->S transition in the adrenal cell cycle. FGF2 elicits a strong mitogenic response in G0/G1-arrested Y1 adrenocortical cells, that includes a) rapid and transient activation of extracellular signal-regulated kinases-mitogen-activated protein kinases (ERK-MAPK) (2 to 10 min), b) transcription activation of c-fos, c-jun and c-myc genes (10 to 30 min), c) induction of c-Fos and c-Myc proteins by 1 h and cyclin D1 protein by 5 h, and d) onset of DNA synthesis stimulation within 8 h. ACTH, itself a weak mitogen, interacts with FGF2 in a complex manner, blocking the FGF2 mitogenic response during the early and middle G1 phase, keeping ERK-MAPK activation and c-Fos and cyclin D1 induction at maximal levels, but post-transcriptionally inhibiting c-Myc expression. c-Fos and c-Jun proteins are mediators in both the strong and the weak mitogenic responses respectively triggered by FGF2 and ACTH. Induction of c-Fos and stimulation of DNA synthesis by ACTH are independent of PKA and are inhibited by the PKC inhibitor GF109203X. In addition, ACTH is a poor activator of ERK-MAPK, but c-Fos induction and DNA synthesis stimulation by ACTH are strongly inhibited by the inhibitor of MEK1 PD98059.
PURPOSE: Outcome of diffuse large B-cell lymphoma (DLBCL) with a germinal center B-cell (GCB) expression profile is superior to that of non-GCB DLBCL. This conclusion is mainly derived from patients with mixed international prognostic index (IPI) risk profiles treated with CHOP-like therapy (cyclophosphamide, doxorubicin, vincristine, and prednisone). We wondered whether the prognostic impact of the expression profile would hold out in a homogeneous cohort of poor-risk DLBCL patients treated with high-dose sequential therapy (HDT) and autologous stem-cell transplantation (ASCT) as first-line therapy. PATIENTS AND METHODS: DLBCL from 66 newly diagnosed poor-risk patients, treated in two sequential prospective Dutch Hemato-Oncology Association (HOVON) trials, were studied retrospectively for expression of CD10, bcl6, MUM1/IRF4, bcl2, Ki67, and CD21+ follicular dendritic cells (FDC) by immunohistochemistry, and for the breakpoints of BCL2, BCL6, and MYC by fluorescent in situ hybridization (FISH). Lymphomas with any follicular component were excluded. RESULTS: A GCB immunophenotype profile was found in 58% and non-GCB immunophenotype profile in 42% of the tumors. Clinical characteristics of both groups were similar. Complete response (CR) rate was higher in patients with CD10+ tumors (58% v 30%; P = .03). A GCB immunophenotype profile, its constituting markers CD10 more than 30% and MUM1 less than 70%, and bcl2 less than 10% were each associated with a better overall survival (OS). FDC networks, equally present in GCB and non-GCB tumors, had superior CR (73% v 31%; P = .01), but disease-free survival rates were lower and there was no difference in OS rates. None of the breakpoints had a prognostic impact on outcome. CONCLUSION: Also in patients with poor-risk DLBCL treated with HDT and ASCT, the GCB immunophenotype and bcl2 expression retained a major impact on survival.
We examined paraffin sections for the expression of interleukin-1 alpha, interleukin-1 beta and tumor necrosis factor-alpha, in 40 cases of Hodgkin's disease. Our purpose was to study the role of these cytokines in the "inflammatory" histological features and "B" symptoms in this disease. Immunohistochemistry with the avidin-biotin-peroxidase complex method was used. The findings were compared with those of 20 cases of non-Hodgkin's lymphomas and of 20 non-neoplastic lymphadenopathies. Evidence for EBV infection and myc and ras oncoproteins expression was also studied in these patients, but no correlation between any of these features and cytokine expression was found. We found a significant correlation between the expression of interleukin-1 beta and several "inflammatory" histological features, as well as between the expression of tumor necrosis factor-alpha and B symptoms and tumor bulk. The differential correlations between these major pro-inflammatory cytokines expression and the "inflammatory" manifestations in Hodgkin's disease are remarkable, considering the complexity of the cytokines composing the cytokine network involved in this disease.