The homeodomain transcription factor CDX2 is a relatively specific immunohistochemical marker for gastrointestinal carcinoma. However, no study has comprehensively examined the relationship between ...CDX2 expression in colon cancer and clinical, pathologic, prognostic, and molecular features, including microsatellite instability and CpG island methylator phenotype (CIMP).
Utilizing 621 colorectal cancers with clinical outcome and molecular data, CDX2 loss was detected in 183 (29%) tumors by immunohistochemistry.
In multivariate logistic regression analysis, CDX2 loss was associated with female gender odds ratio (OR), 3.32; P < 0.0001, CIMP-high (OR, 4.42; P = 0.0003), high tumor grade (OR, 2.69; P = 0.0085), stage IV disease (OR, 2.03; P = 0.019), and inversely with LINE-1 hypomethylation (for a 30% decline; OR, 0.33; P = 0.0031), p53 expression (OR, 0.55; P = 0.011), and beta-catenin activation (OR, 0.60; P = 0.037), but not with body mass index, tumor location, microsatellite instability, BRAF, KRAS, PIK3CA, p21, or cyclooxygenase-2. CDX2 loss was not independently associated with patient survival. However, the prognostic effect of CDX2 loss seemed to differ according to family history of colorectal cancer (P(interaction) = 0.0094). CDX2 loss was associated with high overall mortality (multivariate hazard ratio, 2.40; 95% CI, 1.28-4.51) among patients with a family history of colorectal cancer; no such association was present (multivariate hazard ratio, 0.97; 95% CI, 0.66-1.41) among patients without a family history of colorectal cancer.
CDX2 loss in colorectal cancer is independently associated with female gender, CIMP-high, high-level LINE-1 methylation, high tumor grade, and advanced stage. CDX2 loss may be associated with poor prognosis among patients with a family history of colorectal cancer.
Nup133 belongs to the Y-complex, a key component of the nuclear pore complex (NPC) scaffold. Studies on a null mutation in mice previously revealed that Nup133 is essential for embryonic development ...but not for mouse embryonic stem cell (mESC) proliferation. Using single-pore detection and average NE-fluorescence intensity, we find that Nup133 is dispensable for interphase and postmitotic NPC scaffold assembly in pluripotent mESCs. However, loss of Nup133 specifically perturbs the formation of the nuclear basket as manifested by the absence of Tpr in about half of the NPCs combined with altered dynamics of Nup153. We further demonstrate that its central domain mediates Nup133’s role in assembling Tpr and Nup153 into a properly configured nuclear basket. Our findings thus revisit the role of the Y-complex in pore biogenesis and provide insights into the interplay between NPC scaffold architecture, nuclear basket assembly, and the generation of heterogeneity among NPCs.
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•Nup133 is dispensable for interphase NPC assembly in mESCs•Assembly of Tpr within the basket of all NPCs requires Nup133•Nup133 deficiency increases Nup153 dynamics in vivo•The central domain of Nup133 is required for proper NPC basket assembly and dynamics
Souquet et al. report that Nup133, a structural component of the nuclear pore complex (NPC), is dispensable for NPC scaffold formation during post-mitotic and interphase pore assembly in embryonic stem cells. Yet, they also find that Nup133’s central domain is required for a properly configured nuclear basket in all NPCs.
Recently, many new examples of E3 ubiquitin ligases or E3 enzymes have been found to regulate a host of cellular processes. These E3 enzymes direct the formation of multiubiquitin chains on specific ...protein substrates, and – typically – the subsequent destruction of those proteins. We discuss how the modular architecture of E3 enzymes connects one of two distinct classes of catalytic domains to a wide range of substrate-binding domains. In one catalytic class, a HECT domain transfers ubiquitin directly to substrate bound to a non-catalytic domain. Members of the other catalytic class, found in the SCF, VBC and APC complexes, use a RING finger domain to facilitate ubiquitylation. The separable substrate-recognition domains of E3 enzymes provides a flexible means of linking a conserved ubiquitylation function to potentially thousands of ubiquitylated substrates in eukaryotic cells.
Surprisingly few pathways signal between cells, raising questions about mechanisms for tissue-specific responses. In particular, Wnt ligands signal in many mammalian tissues, including the intestinal ...epithelium, where constitutive signaling causes cancer. Genomewide analysis of DNA cis-regulatory regions bound by the intestine-restricted transcription factor CDX2 in colonic cells uncovered highly significant overrepresentation of sequences that bind TCF4, a transcriptional effector of intestinal Wnt signaling. Chromatin immuno-precipitation confirmed TCF4 occupancy at most such sites and cooccupancy of CDX2 and TCF4 across short distances. A region spanning the single nucleotide polymorphism rs6983267, which lies within a MYC enhancer and confers colorectal cancer risk in humans, represented one of many co-occupied sites. Co-occupancy correlated with intestine-specific gene expression and CDX2 loss reduced TCF4 binding. These results implicate CDX2 in directing TCF4 binding in intestinal cells. Co-occupancy of regulatory regions by signal-effector and tissue-restricted transcription factors may represent a general mechanism for ubiquitous signaling pathways to achieve tissue-specific outcomes.
Structure–activity relationship analysis identified (+)-N-(3-aminopropyl)-N-1-(5-benzyl-3-methyl-4-oxo-1,2thiazolo5,4-dpyrimidin-6-yl)-2-methylpropyl-4-methylbenzamide (AZD4877), from a series of ...novel kinesin spindle protein (KSP) inhibitors, as exhibiting both excellent biochemical potency and pharmaceutical properties suitable for clinical development. The selected compound arrested cells in mitosis leading to the formation of the monopolar spindle phenotype characteristic of KSP inhibition and induction of cellular death. A favorable pharmacokinetic profile and notable in vivo efficacy supported the selection of this compound as a clinical candidate for the treatment of cancer.
To identify proteins that may participate in the activation of the protein kinase Raf, proteins that interact with Raf were selected in a two-hybrid screen. Two members of the 14-3-3 protein family ...were isolated that interacted with both the amino terminal regulatory regions of Raf and the kinase domain of Raf, but did not compete with the guanine nucleotide-binding protein Ras for binding to Raf. 14-3-3 proteins associated with Raf in mammalian cells and accompanied Raf to the membrane in the presence of activated Ras. In yeast cells expressing Raf and MEK, mammalian 14-3-3 β or 14-3-3 ζ activated Raf to a similar extent as did expression of Ras. Therefore, 14-3-3 proteins may participate in or be required for the regulation of Raf function. These findings suggest a role for 14-3-3 proteins in Raf-mediated signal transduction.
Aberrant activation of the canonical WNT/beta-catenin pathway occurs in almost all colorectal cancers and contributes to their growth, invasion and survival. Although dysregulated beta-catenin ...activity drives colon tumorigenesis, further genetic perturbations are required to elaborate full malignant transformation. To identify genes that both modulate beta-catenin activity and are essential for colon cancer cell proliferation, we conducted two loss-of-function screens in human colon cancer cells and compared genes identified in these screens with an analysis of copy number alterations in colon cancer specimens. One of these genes, CDK8, which encodes a member of the mediator complex, is located at 13q12.13, a region of recurrent copy number gain in a substantial fraction of colon cancers. Here we show that the suppression of CDK8 expression inhibits proliferation in colon cancer cells characterized by high levels of CDK8 and beta-catenin hyperactivity. CDK8 kinase activity was necessary for beta-catenin-driven transformation and for expression of several beta-catenin transcriptional targets. Together these observations suggest that therapeutic interventions targeting CDK8 may confer a clinical benefit in beta-catenin-driven malignancies.
We have discovered an
early
mitotic
inhibitor, Emi1, which regulates mitosis by inhibiting the anaphase promoting complex/cyclosome (APC). Emi1 is a conserved F box protein containing a zinc binding ...region essential for APC inhibition. Emi1 accumulates before mitosis and is ubiquitylated and destroyed in mitosis, independent of the APC. Emi1 immunodepletion from cycling
Xenopus extracts strongly delays cyclin B accumulation and mitotic entry, whereas nondestructible Emi1 stabilizes APC substrates and causes a mitotic block. Emi1 binds the APC activator Cdc20, and Cdc20 can rescue an Emi1-induced block to cyclin B destruction. Our results suggest that Emi1 regulates progression through early mitosis by preventing premature APC activation, and may help explain the well-known delay between cyclin B/Cdc2 activation and cyclin B destruction.
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