scholarly journals Reduced Levels of ATF-2 Predispose Mice to Mammary Tumors

2006 ◽  
Vol 27 (5) ◽  
pp. 1730-1744 ◽  
Author(s):  
Toshio Maekawa ◽  
Toshie Shinagawa ◽  
Yuji Sano ◽  
Takahiko Sakuma ◽  
Shintaro Nomura ◽  
...  
Keyword(s):  
Cell Density ◽  
Target Genes ◽  
High Cell Density ◽  
Critical Role ◽  
Susceptibility Gene ◽  
Mammary Tumors ◽  
Mrna Levels ◽  
High Cell ◽  
Wild Type ◽  
Induced Apoptosis

ABSTRACT Transcription factor ATF-2 is a nuclear target of stress-activated protein kinases, such as p38, which are activated by various extracellular stresses, including UV light. Here, we show that ATF-2 plays a critical role in hypoxia- and high-cell-density-induced apoptosis and the development of mammary tumors. Compared to wild-type cells, Atf-2 −/− mouse embryonic fibroblasts (MEFs) were more resistant to hypoxia- and anisomycin-induced apoptosis but remained equally susceptible to other stresses, including UV. Atf-2 −/− and Atf-2 +/− MEFs could not express a group of genes, such as Gadd45α, whose overexpression can induce apoptosis, in response to hypoxia. Atf-2 −/− MEFs also had a higher saturation density than wild-type cells and expressed lower levels of Maspin, the breast cancer tumor suppressor, which is also known to enhance cellular sensitivity to apoptotic stimuli. Atf-2 −/− MEFs underwent a lower degree of apoptosis at high cell density than wild-type cells. Atf-2 +/− mice were highly prone to mammary tumors that expressed reduced levels of Gadd45α and Maspin. The ATF-2 mRNA levels in human breast cancers were lower than those in normal breast tissue. Thus, ATF-2 acts as a tumor susceptibility gene of mammary tumors, at least partly, by activating a group of target genes, including Maspin and Gadd45α.

Role of procollagen mRNA levels in controlling the rate of procollagen synthesis

1983 ◽  
Vol 3 (2) ◽  
pp. 241-249
Author(s):  
L B Rowe ◽  
R I Schwarz
Keyword(s):  
Cell Density ◽  
High Cell Density ◽  
Control Point ◽  
Relative Increase ◽  
Limiting Factor ◽  
Mrna Levels ◽  
Primary Control ◽  
High Cell ◽  
Mrna Induction ◽  
Tendon Cells

Two factors must be present for primary avian tendon cells to commit 50% of their total protein production to procollagen: ascorbate and high cell density. Scorbutic primary avian tendon cells at high cell density (greater than 4 X 10(4) cells per cm2) responded to the addition of ascorbate by a sixfold increase in the rate of procollagen synthesis. The kinetics were biphasic, showing a slow increase during the first 12 h followed by a more rapid rise to a maximum after 36 to 48 h. In contrast, after ascorbate addition, the level of accumulated cytoplasmic procollagen mRNA (alpha 2) showed a 12-h lag followed by a slow linear increase requiring 60 to 72 h to reach full induction. At all stages of the induction process, the relative increase in the rate of procollagen synthesis over the uninduced state exceeded the relative increase in the accumulation of procollagen mRNA. A similar delay in mRNA induction was observed when the cells were grown in an ascorbate-containing medium but the cell density was allowed to increase. In all cases, the rate of procollagen synthesis peaked approximately 24 h before the maximum accumulation of procollagen mRNA. The kinetics for the increase in procollagen synthesis are not, therefore, in agreement with the simple model that mRNA levels are the rate-limiting factor in the collagen pathway. We propose that the primary control point is at a later step. Further support for this idea comes from inhibitor studies, using alpha, alpha'-dipyridyl to block ascorbate action. In the presence of 0.3 mM alpha, alpha'-dipyridyl there was a specific two- to threefold decrease in procollagen production after 4 h, but this was unaccompanied by a drop in procollagen mRNA levels. Therefore, inhibitor studies give further support to the idea that primary action of ascorbate is to release a post-translational block.

scholarly journals Control of the Type 3 Secretion System in Vibrio harveyi by Quorum Sensing through Repression of ExsA

2010 ◽  
Vol 76 (15) ◽  
pp. 4996-5004 ◽  
Author(s):  
Christopher M. Waters ◽  
Julie T. Wu ◽  
Meghan E. Ramsey ◽  
Rebecca C. Harris ◽  
Bonnie L. Bassler
Keyword(s):  
Quorum Sensing ◽  
Cell Density ◽  
Target Genes ◽  
High Cell Density ◽  
Vibrio Harveyi ◽  
Secretion System ◽  
High Cell ◽  
Type 3 Secretion System ◽  
Type 3 ◽  
Low Cell Density

ABSTRACT The type 3 secretion system (T3SS) genes of Vibrio harveyi are activated at low cell density and repressed at high cell density by quorum sensing (QS). Repression requires LuxR, the master transcriptional regulator of QS-controlled genes. Here, we determine the mechanism underlying the LuxR repression of the T3SS system. Using a fluorescence-based cell sorting approach, we isolated V. harveyi mutants that are unable to express T3SS genes at low cell density and identified two mutations in the V. harveyi exsBA operon. While LuxR directly represses the expression of exsBA, complementation and epistasis analyses reveal that it is the repression of exsA expression, but not exsB expression, that is responsible for the QS-mediated repression of T3SS genes at high cell density. The present work further defines the genes in the V. harveyi QS regulon and elucidates a mechanism demonstrating how multiple regulators can be linked in series to direct the expression of QS target genes specifically at low or high cell density.

scholarly journals Developmental regulation of the alpha-mannosidase gene in Dictyostelium discoideum: control is at the level of transcription and is affected by cell density.

1991 ◽  
Vol 11 (6) ◽  
pp. 3339-3347 ◽  
Author(s):  
J Schatzle ◽  
A Rathi ◽  
M Clarke ◽  
J A Cardelli
Keyword(s):  
Cell Density ◽  
Dictyostelium Discoideum ◽  
High Cell Density ◽  
Specific Activity ◽  
Developmental Regulation ◽  
Cdna Probe ◽  
Mrna Levels ◽  
High Cell ◽  
Enzyme Specific Activity ◽  
Negative Mutant

In Dictyostelium discoideum, there is a group of genes that are expressed following starvation and when exponentially growing cells reach high densities. We have examined the expression of one of these genes, alpha-mannosidase. Using an alpha-mannosidase cDNA probe in Northern (RNA) blot analysis, we have shown that the previously observed increase in alpha-mannosidase enzyme-specific activity during development is due to an increase in the levels of alpha-mannosidase mRNA. mRNA levels reach a maximum by 8 h of development and then begin to decline by 14 to 22 h. Using nuclear run-on analysis, we have found that this gene is regulated at the level of transcription. We also examined the effects of cell-cell contacts, cyclic AMP levels, and protein synthesis on expression of this gene and found that they were not critical in regulating its expression. However, cell density did play a major role in the expression of alpha-mannosidase. High cell density or the presence of buffer conditioned by high-density cells was sufficient to induce expression of alpha-mannosidase, indicating that this is one of the prestarvation response genes. Finally, the alpha-mannosidase gene was not expressed in aggregation-negative mutant strain HMW 404.

scholarly journals Quorum Sensing-Mediated and Growth Phase-Dependent Regulation of Metabolic Pathways in Hafnia alvei H4

2021 ◽  
Vol 12 ◽  
Author(s):  
Congyang Yan ◽  
Xue Li ◽  
Gongliang Zhang ◽  
Yaolei Zhu ◽  
Jingran Bi ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Cell Density ◽  
Growth Phase ◽  
Metabolic Pathways ◽  
High Cell Density ◽  
Dependent Manner ◽  
High Cell ◽  
Wild Type ◽  
Hafnia Alvei ◽  
Density Dependent

Quorum sensing (QS) is a widespread regulatory mechanism in bacteria used to coordinate target gene expression with cell density. Thus far, little is known about the regulatory relationship between QS and cell density in terms of metabolic pathways in Hafnia alvei H4. In this study, transcriptomics analysis was performed under two conditions to address this question. The comparative transcriptome of H. alvei H4 wild-type at high cell density (OD600 = 1.7) relative to low cell density (OD600 = 0.3) was considered as growth phase-dependent manner (GPDM), and the transcriptome profile of luxI/R deletion mutant (ΔluxIR) compared to the wild-type was considered as QS-mediated regulation. In all, we identified 206 differentially expressed genes (DEGs) mainly presented in chemotaxis, TCA cycle, two-component system, ABC transporters and pyruvate metabolism, co-regulated by the both density-dependent regulation, and the results were validated by qPCR and swimming phenotypic assays. Aside from the co-regulated DEGs, we also found that 59 DEGs, mediated by density-independent QS, function in pentose phosphate and histidine metabolism and that 2084 cell-density-dependent DEGs involved in glycolysis/gluconeogenesis and phenylalanine metabolism were influenced only by GPDM from significantly enriched analysis of transcriptome data. The findings provided new information about the interplay between two density-dependent metabolic regulation, which could assist with the formulation of control strategies for this opportunistic pathogen, especially at high cell density.

Developmental regulation of the alpha-mannosidase gene in Dictyostelium discoideum: control is at the level of transcription and is affected by cell density

1991 ◽  
Vol 11 (6) ◽  
pp. 3339-3347
Author(s):  
J Schatzle ◽  
A Rathi ◽  
M Clarke ◽  
J A Cardelli
Keyword(s):  
Cell Density ◽  
Dictyostelium Discoideum ◽  
High Cell Density ◽  
Specific Activity ◽  
Developmental Regulation ◽  
Cdna Probe ◽  
Mrna Levels ◽  
High Cell ◽  
Enzyme Specific Activity ◽  
Negative Mutant

In Dictyostelium discoideum, there is a group of genes that are expressed following starvation and when exponentially growing cells reach high densities. We have examined the expression of one of these genes, alpha-mannosidase. Using an alpha-mannosidase cDNA probe in Northern (RNA) blot analysis, we have shown that the previously observed increase in alpha-mannosidase enzyme-specific activity during development is due to an increase in the levels of alpha-mannosidase mRNA. mRNA levels reach a maximum by 8 h of development and then begin to decline by 14 to 22 h. Using nuclear run-on analysis, we have found that this gene is regulated at the level of transcription. We also examined the effects of cell-cell contacts, cyclic AMP levels, and protein synthesis on expression of this gene and found that they were not critical in regulating its expression. However, cell density did play a major role in the expression of alpha-mannosidase. High cell density or the presence of buffer conditioned by high-density cells was sufficient to induce expression of alpha-mannosidase, indicating that this is one of the prestarvation response genes. Finally, the alpha-mannosidase gene was not expressed in aggregation-negative mutant strain HMW 404.

scholarly journals Myxococcus xanthus sasN Encodes a Regulator That Prevents Developmental Gene Expression during Growth

1998 ◽  
Vol 180 (23) ◽  
pp. 6215-6223 ◽  
Author(s):  
Di Xu ◽  
Chun Yang ◽  
Heidi B. Kaplan
Keyword(s):  
Cell Density ◽  
Fruiting Body ◽  
Growth And Development ◽  
High Cell Density ◽  
Myxococcus Xanthus ◽  
High Cell ◽  
Wild Type ◽  
Hydrophobic Region ◽  
Body Development ◽  
Fruiting Body Development

ABSTRACT Myxococcus xanthus multicellular fruiting body development is initiated by nutrient limitation at high cell density. Five clustered point mutations (sasB5, -14, -15, -16, and -17) can bypass the starvation and high-cell-density requirements for expression of the4521 developmental reporter gene. These mutants express4521 at high levels during growth and development in anasgB background, which is defective in generation of the cell density signal, A signal. A 1.3-kb region of the sasBlocus cloned from the wild-type chromosome restored the SasB+ phenotype to the five mutants. DNA sequence analysis of the 1.3-kb region predicted an open reading frame, designated SasN. The N terminus of SasN appears to contain a strongly hydrophobic region and a leucine zipper motif. SasN showed no significant sequence similarities to known proteins. A strain containing a newly constructedsasN-null mutation and Ω4521 Tn5lac in an otherwise wild-type background expressed 4521 at a high level during growth and development. A similar sasN-null mutant formed abnormal fruiting bodies and sporulated at about 10% the level of wild type. These data indicate that the wild-typesasN gene product is necessary for normal M. xanthus fruiting body development and functions as a critical regulator that prevents 4521 expression during growth.

scholarly journals Tumor suppressor protein Lgl mediates G1 cell cycle arrest at high cell density by forming an Lgl-VprBP-DDB1 complex

2015 ◽  
Vol 26 (13) ◽  
pp. 2426-2438 ◽  
Author(s):  
Kazunari Yamashita ◽  
Mariko Ide ◽  
Kana T. Furukawa ◽  
Atsushi Suzuki ◽  
Hisashi Hirano ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Tumor Suppressor ◽  
Epithelial Cells ◽  
Cell Density ◽  
Cell Polarity ◽  
High Cell Density ◽  
Critical Role ◽  
Central Component ◽  
G1 Arrest ◽  
High Cell

Lethal giant larvae (Lgl) is an evolutionarily conserved tumor suppressor whose loss of function causes disrupted epithelial architecture with enhanced cell proliferation and defects in cell polarity. A role for Lgl in the establishment and maintenance of cell polarity via suppression of the PAR-aPKC polarity complex is established; however, the mechanism by which Lgl regulates cell proliferation is not fully understood. Here we show that depletion of Lgl1 and Lgl2 in MDCK epithelial cells results in overproliferation and overproduction of Lgl2 causes G1 arrest. We also show that Lgl associates with the VprBP-DDB1 complex independently of the PAR-aPKC complex and prevents the VprBP-DDB1 subunits from binding to Cul4A, a central component of the CRL4 [VprBP] ubiquitin E3 ligase complex implicated in G1- to S-phase progression. Consistently, depletion of VprBP or Cul4 rescues the overproliferation of Lgl-depleted cells. In addition, the affinity between Lgl2 and the VprBP-DDB1 complex increases at high cell density. Further, aPKC-mediated phosphorylation of Lgl2 negatively regulates the interaction between Lgl2 and VprBP-DDB1 complex. These results suggest a mechanism protecting overproliferation of epithelial cells in which Lgl plays a critical role by inhibiting formation of the CRL4 [VprBP] complex, resulting in G1 arrest.

scholarly journals Role of procollagen mRNA levels in controlling the rate of procollagen synthesis.

1983 ◽  
Vol 3 (2) ◽  
pp. 241-249 ◽  
Author(s):  
L B Rowe ◽  
R I Schwarz
Keyword(s):  
Cell Density ◽  
High Cell Density ◽  
Control Point ◽  
Relative Increase ◽  
Limiting Factor ◽  
Mrna Levels ◽  
Primary Control ◽  
High Cell ◽  
Mrna Induction ◽  
Tendon Cells

Two factors must be present for primary avian tendon cells to commit 50% of their total protein production to procollagen: ascorbate and high cell density. Scorbutic primary avian tendon cells at high cell density (greater than 4 X 10(4) cells per cm2) responded to the addition of ascorbate by a sixfold increase in the rate of procollagen synthesis. The kinetics were biphasic, showing a slow increase during the first 12 h followed by a more rapid rise to a maximum after 36 to 48 h. In contrast, after ascorbate addition, the level of accumulated cytoplasmic procollagen mRNA (alpha 2) showed a 12-h lag followed by a slow linear increase requiring 60 to 72 h to reach full induction. At all stages of the induction process, the relative increase in the rate of procollagen synthesis over the uninduced state exceeded the relative increase in the accumulation of procollagen mRNA. A similar delay in mRNA induction was observed when the cells were grown in an ascorbate-containing medium but the cell density was allowed to increase. In all cases, the rate of procollagen synthesis peaked approximately 24 h before the maximum accumulation of procollagen mRNA. The kinetics for the increase in procollagen synthesis are not, therefore, in agreement with the simple model that mRNA levels are the rate-limiting factor in the collagen pathway. We propose that the primary control point is at a later step. Further support for this idea comes from inhibitor studies, using alpha, alpha'-dipyridyl to block ascorbate action. In the presence of 0.3 mM alpha, alpha'-dipyridyl there was a specific two- to threefold decrease in procollagen production after 4 h, but this was unaccompanied by a drop in procollagen mRNA levels. Therefore, inhibitor studies give further support to the idea that primary action of ascorbate is to release a post-translational block.

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