Non-genic inheritance of cellular handedness

Development ◽  
1989 ◽  
Vol 105 (3) ◽  
pp. 447-456 ◽  
Author(s):  
E.M. Nelsen ◽  
J. Frankel ◽  
L.M. Jenkins
Keyword(s):  
Positional Information ◽  
Regulatory Elements ◽  
Genetic Change ◽  
Surface Structures ◽  
Phenotypic Alteration ◽  
Left Handed ◽  
A Cell ◽  
Usual Order ◽  
Genic Control ◽  
Rule Out

Ciliates exhibit an asymmetry in arrangement of surface structures around the cell which could be termed handedness. If the usual order of placement of structures defines a ‘right-handed’ (RH) cell, then a cell with this order reversed would be ‘left-handed’ (LH). Such LH forms appear to be produced in Tetrahymena thermophila through aberrant reorganization of homopolar doublets back to the singlet condition. Four clones of LH forms were selected and subjected to genetic analysis to test whether this drastic phenotypic alteration resulted from a nuclear genetic change. The results of this analysis indicate that the change in handedness is not due to a genetic change in either the micronucleus or macronucleus. The LH form can, under certain circumstances, revert to the RH form, but typically it propagates itself across both vegetative and sexual generations with similar fidelity. While this analysis does not formally rule out certain possibilities of nuclear genic control involving regulatory elements transmitted through the cytoplasm, when the circumstances of origin and propagation of the LH condition are taken into account direct cortical perpetuation seems far more likely. Here we outline a conceptual framework centred on the idea of longitudinally propagated positional information; the positive evidence supporting this idea as well as further application of the idea itself are presented in the accompanying paper.

Effect of PCMBS on CO2permeability of Xenopus oocytes expressing aquaporin 1 or its C189S mutant

1998 ◽  
Vol 275 (6) ◽  
pp. C1481-C1486 ◽  
Author(s):  
Gordon J. Cooper ◽  
Walter F. Boron
Keyword(s):  
Carbonic Anhydrase ◽  
Intracellular Ph ◽  
Xenopus Oocytes ◽  
Membrane Lipid ◽  
Wild Type ◽  
Aquaporin 1 ◽  
Gas Channel ◽  
A Cell ◽  
Pass Through ◽  
Rule Out

A recent study on Xenopus oocytes [N. L. Nakhoul, M. F. Romero, B. A. Davis, and W. F. Boron. Am. J. Physiol. 274 ( Cell Physiol. 43): C543–548, 1998] injected with carbonic anhydrase showed that expressing aquaporin 1 (AQP1) increases by ∼40% the rate at which exposing the cell to CO2 causes intracellular pH to fall. This observation is consistent with several interpretations. Overexpressing AQP1 might increase apparent CO2 permeability by 1) allowing CO2 to pass through AQP1, 2) stimulating injected carbonic anhydrase, 3) enhancing the CO2 solubility of the membrane’s lipid, or 4) increasing the expression of a native “gas channel.” The purpose of the present study was to distinguish among these possibilities. We found that expressing the H2O channel AQP1 in Xenopus oocytes increases the CO2 permeability of oocytes in an expression-dependent fashion, whereas expressing the K+ channel ROMK1 has no effect. The mercury derivative p-chloromercuriphenylsulfonic acid (PCMBS), which inhibits the H2O movement through AQP1, also blocks the AQP1-dependent increase in CO2 permeability. The mercury-insensitive C189S mutant of AQP1 increases the CO2 permeability of the oocyte to the same extent as does the wild-type channel. However, the C189S-dependent increase in CO2permeability is unaffected by treatment with PCMBS. These data rule out options 2–4 listed above. Thus our results suggest that CO2passes through the pore of AQP1 and are the first data to demonstrate that a gas can enter a cell by a means other than diffusing through the membrane lipid.

scholarly journals MacroH2A histone variants modulate enhancer activity to repress oncogenic programs and cellular reprogramming

2021 ◽  
Author(s):  
Alexandre Gaspar-Maia ◽  
Wazim Mohammed Ismail ◽  
Amelia Mazzone ◽  
Jagneet Kaur ◽  
Stephanie Safgren ◽  
...  
Keyword(s):  
Regulatory Elements ◽  
Histone Variants ◽  
Cellular Reprogramming ◽  
Negative Regulator ◽  
Cellular Heterogeneity ◽  
Enhancer Activity ◽  
Active Enhancer ◽  
A Cell ◽  
Cell Type Specific

Abstract Considerable efforts have been made to characterize active enhancer elements, which can be annotated by accessible chromatin and H3 lysine 27 acetylation (H3K27ac). However, apart from poised enhancers that are observed in early stages of development and putative silencers, the functional significance of cis-regulatory elements lacking H3K27ac is poorly understood. Here we show that macroH2A histone variants mark a subset of enhancers in normal and cancer cells, which we coined ‘macroH2A-Bound Enhancers’, that negatively modulate enhancer activity. We find macroH2A variants enriched at enhancer elements that are devoid of H3K27ac in a cell type-specific manner, indicating a role for macroH2A at inactive enhancers to maintain cell identity. In following, reactivation of macro-bound enhancers is associated with oncogenic programs in breast cancer and its repressive role is correlated with the activity of macroH2A2 as a negative regulator of BRD4 chromatin occupancy. Finally, through single cell epigenomic profiling, we show that the loss of macroH2A2 leads to increased cellular heterogeneity that may help to explain the role of macroH2A variants in defining oncogenic transcriptional dependencies.

scholarly journals A Cell-Based High-Throughput Assay for the Screening of Small-Molecule Inhibitors of p53–MDM2 Interaction

2011 ◽  
Vol 16 (4) ◽  
pp. 450-456 ◽  
Author(s):  
Jing Li ◽  
Shuyong Zhang ◽  
Linghuan Gao ◽  
Ying Chen ◽  
Xin Xie
Keyword(s):  
High Throughput ◽  
Luciferase Reporter ◽  
Reporter System ◽  
Direct Inhibition ◽  
A Cell ◽  
Luciferase Reporter System ◽  
Novel Strategy ◽  
High Throughput Assay ◽  
Two Hybrid ◽  
Rule Out

The p53 tumor suppressor is a potent transcription factor that regulates cell growth inhibition and apoptosis. The oncoprotein MDM2 suppresses p53 activity by direct inhibition of its transcriptional activity and enhances the degradation of p53 via the ubiquitin–proteosome pathway. Overexpression of MDM2, found in many human tumors, impairs p53-mediated cell death effectively. Inhibition of the p53–MDM2 interaction can stabilize p53 and may offer a novel strategy for cancer therapy. To search for new inhibitors of the p53–MDM2 interaction, the authors developed a cell-based high-throughput assay system based on mammalian two-hybrid technology. They also used a dual-luciferase reporter system to rule out false- positive hits due to the cytotoxic effect of compounds. Using this assay, they screened a library consisting of 3840 compounds and identified one compound that activates p53 pathway and induces growth arrest in tumor cells.

Transducing positional information to the Hox genes: critical interaction of cdx gene products with position-sensitive regulatory elements

Development ◽  
1998 ◽  
Vol 125 (22) ◽  
pp. 4349-4358 ◽  
Author(s):  
J. Charite ◽  
W. de Graaff ◽  
D. Consten ◽  
M.J. Reijnen ◽  
J. Korving ◽  
...  
Keyword(s):  
Binding Sites ◽  
Hox Genes ◽  
Regulatory Element ◽  
Ectopic Expression ◽  
Positional Information ◽  
Regulatory Elements ◽  
Gene Products ◽  
Anteroposterior Patterning

Studies of pattern formation in the vertebrate central nervous system indicate that anteroposterior positional information is generated in the embryo by signalling gradients of an as yet unknown nature. We searched for transcription factors that transduce this information to the Hox genes. Based on the assumption that the activity levels of such factors might vary with position along the anteroposterior axis, we devised an in vivo assay to detect responsiveness of cis-acting sequences to such differentially active factors. We used this assay to analyze a Hoxb8 regulatory element, and detected the most pronounced response in a short stretch of DNA containing a cluster of potential CDX binding sites. We show that differentially expressed DNA binding proteins are present in gastrulating embryos that bind to these sites in vitro, that cdx gene products are among these, and that binding site mutations that abolish binding of these proteins completely destroy the ability of the regulatory element to drive regionally restricted expression in the embryo. Finally, we show that ectopic expression of cdx gene products anteriorizes expression of reporter transgenes driven by this regulatory element, as well as that of the endogenous Hoxb8 gene, in a manner that is consistent with them being essential transducers of positional information. These data suggest that, in contrast to Drosophila Caudal, vertebrate cdx gene products transduce positional information directly to the Hox genes, acting through CDX binding sites in their enhancers. This may represent the ancestral mode of action of caudal homologues, which are involved in anteroposterior patterning in organisms with widely divergent body plans and modes of development.

scholarly journals Cell structure and cell activity

1930 ◽  
Vol 107 (749) ◽  
pp. 168-181 ◽  
Keyword(s):  
Cell Structure ◽  
Succinic Dehydrogenase ◽  
Cell Activity ◽  
Lactic Dehydrogenase ◽  
Surface Structures ◽  
Catechol Oxidase ◽  
Phosphate Solution ◽  
Pronounced Change ◽  
A Cell ◽  
Alkaline Phosphate

The work of Batelli and Stern and of of Warburg has made clear the importance of surface structures in tissue oxidations, and a survey of oxidation systems as a whole show that there must be a considerable grading in complexity and stability of such structures. Agents such as those which oxidise the purine bases or aldehydes, are extractable from the cell; others have not yet been dissociated from the tissues. So many enzymes can be extracted from the cell only by means which must inevitably affect its structure that its is surprising to find that cell activity (or activity of its catalysts) is at all dependent upon cell structure. Disintegration of a cell, the breaking down of cell membranes, will certainly bring about as A. V. Hill (1928) has pointed out, a biochemical chaos and a medley of reactions. Catalysts will be brought into contact with substrates previously held remote from them. The cell end products will change in type and quantity. But if by activity of a cell is meant the activity of its catalysts, mechanical disintegration of the cell will not, in itself, be expressed to bring about any pronounced change. Muscle ground with sand exhibits a very good oxygen uptake in presence of para-phenylenediamine (Keilin, 1929). A number of de-hydrogenases may be extracted from tissues by shaking or maceration in saline or alkaline phosphate solution. Succinic dehydrogenase can be obtained from muscle and lactic dehydrogenase from yeast in this way. Oxidases of compounds of the aromatic type, e. g. , catechol oxidase or tyrosinase appear to act independently of the cell as a whole; so do peroxidase and the hydrolytic ferments. Failure to extract any enzyme would seem to be due to ignorance of a suitable method of elution from the tissue.

Homozygous Deletions Can Be Used to Define a Cell Death Specific Gene Expression Signature Able to Predict Outcome in Myeloma

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 2725-2725
Author(s):  
Nicholas J Dickens ◽  
Brian Walker ◽  
Paola E Leone ◽  
Matthew W Jenner ◽  
Faith Davies ◽  
...  
Keyword(s):  
Gene Expression Signature ◽  
Staging System ◽  
Genetic Change ◽  
Biological Data ◽  
Specific Gene ◽  
Genetic Changes ◽  
Biologically Relevant ◽  
A Cell ◽  
International Staging System ◽  
Homozygous Deletions

Abstract Defining biologically relevant prognostic indices in myeloma is a challenge. The International Staging System (ISS) is important but based on simple clinical data. Cytogenetics, in particular switch translocations and 17p-, are more important biologically, being based on underlying genetic changes. However, these changes do not capture all of the important biological data and so signatures based on global expression analysis have been developed to address these shortcomings. Most signatures to date have been based on expression features correlated with outcome rather than using structural genetic change to define biologically relevant expression features and, as such, although predictive, they may be acting as “bystander” markers rather than being pathologically important themselves. We have used homozygous deletions (HD) to define relevant genes and gene signatures predictive of outcome in a large homogeneously treated set of myeloma patients.

Transfection of calcitonin gene regulatory elements into a cell culture model of the C cell

1990 ◽  
Vol 5 (2) ◽  
pp. 165-171 ◽  
Author(s):  
Gilbert J. Cote ◽  
Ronald V. Abruzzese ◽  
Robert F. Gagel ◽  
CEES J. M. Lips
Keyword(s):  
Cell Culture ◽  
Regulatory Elements ◽  
Cell Culture Model ◽  
C Cell ◽  
Culture Model ◽  
Calcitonin Gene ◽  
Gene Regulatory Elements ◽  
A Cell ◽  
Gene Regulatory

scholarly journals The yeast centrosome translates the positional information of the anaphase spindle into a cell cycle signal

2007 ◽  
Vol 179 (3) ◽  
pp. 423-436 ◽  
Author(s):  
Hiromi Maekawa ◽  
Claire Priest ◽  
Johannes Lechner ◽  
Gislene Pereira ◽  
Elmar Schiebel
Keyword(s):  
Spindle Pole Body ◽  
Coiled Coil ◽  
Positional Information ◽  
Spindle Pole ◽  
Mitotic Exit ◽  
Spindle Orientation ◽  
Additional Function ◽  
A Cell ◽  
Cytoplasmic Microtubules ◽  
Guanosine Triphosphatase

The spindle orientation checkpoint (SPOC) of budding yeast delays mitotic exit when cytoplasmic microtubules (MTs) are defective, causing the spindle to become misaligned. Delay is achieved by maintaining the activity of the Bfa1–Bub2 guanosine triphosphatase–activating protein complex, an inhibitor of mitotic exit. In this study, we show that the spindle pole body (SPB) component Spc72, a transforming acidic coiled coil–like molecule that interacts with the γ-tubulin complex, recruits Kin4 kinase to both SPBs when cytoplasmic MTs are defective. This allows Kin4 to phosphorylate the SPB-associated Bfa1, rendering it resistant to inactivation by Cdc5 polo kinase. Consistently, forced targeting of Kin4 to both SPBs delays mitotic exit even when the anaphase spindle is correctly aligned. Moreover, we present evidence that Spc72 has an additional function in SPOC regulation that is independent of the recruitment of Kin4. Thus, Spc72 provides a missing link between cytoplasmic MT function and components of the SPOC.

scholarly journals Reprogramming of the FOXA1 cistrome in treatment-emergent neuroendocrine prostate cancer

2020 ◽  
Author(s):  
Sylvan C. Baca ◽  
David Y. Takeda ◽  
Ji-Heui Seo ◽  
Justin Hwang ◽  
Sheng Yu Ku ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Histone Modifications ◽  
Ectopic Expression ◽  
Resistance Mechanism ◽  
Regulatory Elements ◽  
Common Mechanism ◽  
Enhancer Activity ◽  
Adaptive Resistance ◽  
Neuroendocrine Prostate Cancer ◽  
A Cell

AbstractLineage plasticity, the ability of a cell to alter its identity, is an increasingly common mechanism of adaptive resistance to targeted therapy in cancer1,2. An archetypal example is the development of neuroendocrine prostate cancer (NEPC) after treatment of prostate adenocarcinoma (PRAD) with inhibitors of androgen signaling. NEPC is an aggressive variant of prostate cancer that aberrantly expresses genes characteristic of neuroendocrine (NE) tissues and no longer depends on androgens. To investigate the epigenomic basis of this resistance mechanism, we profiled histone modifications in NEPC and PRAD patient-derived xenografts (PDXs) using chromatin immunoprecipitation and sequencing (ChIP-seq). We identified a vast network of cis-regulatory elements (N~15,000) that are recurrently activated in NEPC. The FOXA1 transcription factor (TF), which pioneers androgen receptor (AR) chromatin binding in the prostate epithelium3,4, is reprogrammed to NE-specific regulatory elements in NEPC. Despite loss of dependence upon AR, NEPC maintains FOXA1 expression and requires FOXA1 for proliferation and expression of NE lineage-defining genes. Ectopic expression of the NE lineage TFs ASCL1 and NKX2-1 in PRAD cells reprograms FOXA1 to bind to NE regulatory elements and induces enhancer activity as evidenced by histone modifications at these sites. Our data establish the importance of FOXA1 in NEPC and provide a principled approach to identifying novel cancer dependencies through epigenomic profiling.

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