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At least 343 records · Page 19Linked to original sources
PubMed1993

Beta-adrenergic mechanisms affect cell division and differentiation in cultured chick lens epithelial cells.

Primary cultures of chick lens annular pad (CLAP) cells were exposed to beta-adrenergic drugs and lipid soluble cAMP analogues. In dose-dependent manners, these agents inhibited re-entry into the cell cycle when these normally post-mitotic cells were cultured in the presence of serum. The inhibition of cell division was evidenced by a lack of DNA accumulation and greatly reduced tritiated thymidine incorporation into DNA. Treated cells were also largely inhibited from spreading onto the substrate. Instead, the epithelial monolayers originally placed into culture formed nearly spherical aggregates. Treated cultures continued to synthesize crystallins and exhibited increased levels of a 49-kDa cytoskeletal protein which accumulates in fiber cells. These results indicate that beta-adrenergic mechanisms may be involved in regulating cell division and terminal differentiation of lens fiber cells.

Animals↗
PubMed1981

Regulation of cell division and of tyrosinase in B16 melanoma cells by imidazole: a possible role for the concept of metabolite gene regulation in mammalian cells.

Results of hemacytometer cell counts and of tyrosinase measurements made by the Pomerantz method demonstrate that imidazole added to the medium of cultured B16 mouse melanoma cells can stimulate tyrosinase specific activity and inhibit cell division. These effects are greater than with adenosine 3',5' cyclic monophosphate (cAMP) or the cAMP-phosphodiesterase inhibitor theophylline. The effects of imidazole on cell division and tyrosinase are enhanced by theophylline and antagonized by cAMP. Cyclic AMP-phosphodiesterase activity in cell-free extracts can be inhibited by theophylline and stimulated by imidazole. However, imidazole does not affect cAMP-phosphodiesterase specific activity in vivo, nor does it affect intracellular cAMP concentrations as determined by competitive protein-binding assays. In contrast, the specific activity of cAMP-phosphodiesterase in vivo is stimulated by cAMP and theophylline, supporting the hypothesis that cAMP and agents which increase intracellular cAMP concentrations induce the synthesis of cAMP-phosphodiesterase. Studies with actinomycin-D and cycloheximide support the hypothesis that cAMP can also mediate posttranslational activation of tyrosinase. Similar experiments suggest that imidazole, or a derivative thereof, can induce the synthesis of tyrosinase at the pretranslational level of control. We hypothesize that this type of regulation (pretranslational) by imidazole may define a role for the concept of "Metabolite Gene Regulation" (MGR), in mammalian cells.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1986

The effect of Michler's ketone on cell division, chromosome number and structure in cultured Chinese hamster cells.

The industrial chemical Michler's ketone (MK) has been examined for its ability to induce abnormalities of mitotic cell division and the production of chromosomal aberrations and aneuploidy. MK was shown to produce aberrant cell division stages in cultured mammalian cells probably by interference with centrosome replication leading to the production of monopolar spindles during metaphase, and multipolar telophase spindles, in the first division after exposure. Cells in the second division after exposure to MK showed increased levels of chromosome aneuploidy which is presumed to result from aberrant cell division. There was also some evidence of increased levels of chromosome structural aberrations at concentrations of 1.5 microgram/ml.

Aneuploidy↗
PubMed2002

The endocytic protein alpha-Adaptin is required for numb-mediated asymmetric cell division in Drosophila.

During asymmetric cell division in Drosophila sensory organ precursor cells, the Numb protein localizes asymmetrically and segregates into one daughter cell, where it influences cell fate by repressing signal transduction via the Notch receptor. We show here that Numb acts by polarizing the distribution of alpha-Adaptin, a protein involved in receptor-mediated endocytosis. alpha-Adaptin binds to Numb and localizes asymmetrically in a Numb-dependent fashion. Mutant forms of alpha-Adaptin that no longer bind to Numb fail to localize asymmetrically and cause numb-like defects in asymmetric cell division. Our results suggest a model in which Numb influences cell fate by downregulating Notch through polarized receptor-mediated endocytosis, since Numb also binds to the intracellular domain of Notch.

Adaptor Protein Complex alpha Subunits↗
PubMed1988

Division behavior and shape changes in isogenic ftsZ, ftsQ, ftsA, pbpB, and ftsE cell division mutants of Escherichia coli during temperature shift experiments.

Isogenic ftsZ, ftsQ, ftsA, pbpB, and ftsE cell division mutants of Escherichia coli were compared with their parent strain in temperature shift experiments. To improve detection of phenotypic differences in division behavior and cell shape, the strains were grown in glucose-minimal medium with a decreased osmolality (about 100 mosM). Already at the premissive temperature, all mutants, particularly the pbpB and ftsQ mutants, showed an increased average cell length and cell mass. The pbpB and ftsQ mutants also exhibited a prolonged duration of the constriction period. All strains, except ftsZ, continued to initiate new constrictions at 42 degrees C, suggesting the involvement of FtsZ in an early step of the constriction process. The new constrictions were blunt in ftsQ and more pronounced in ftsA and pbpB filaments, which also had elongated median constrictions. Whereas the latter strains showed a slow recovery of cell division after a shift back to the permissive temperature, ftsZ and ftsQ filaments recovered quickly. Recovery of filaments occurred in all strains by the separation of newborn cells with an average length of two times LO, the length of newborn cells at the permissive temperature. The increased size of the newborn cells could indicate that the cell division machinery recovers too slowly to create normal-sized cells. Our results indicate a phenotypic resemblance between ftsA and pbpB mutants and suggest that the cell division gene products function in the order FtsZ-FtsQ-FtsA, PBP3. The ftsE mutant continued to constrict and divide at 42 degrees C, forming short filaments, which recovered quickly after a shift back to the permissive temperature. After prolonged growth at 42 degree C, chains of cells, which eventually swelled up, were formed. Although the ftsE mutant produced filaments in broth medium at the restrictive temperature, it cannot be considered a cell division mutant under the presently applied conditions.

Bacterial Proteins↗
PubMed2003

A novel transmembrane protein recruits numb to the plasma membrane during asymmetric cell division.

Numb, an evolutionarily conserved cell fate-determining factor, plays a pivotal role in the development of Drosophila and vertebrate nervous systems. Despite lacking a transmembrane segment, Numb is associated with the cell membrane during the asymmetric cell division of Drosophila neural precursor cells and is selectively partitioned to one of the two progeny cells from a binary cell division. Numb contains an N-terminal phosphotyrosine-binding (PTB) domain that is essential for both the asymmetric localization and the fate specification function of Numb. We report here the isolation and characterization of a novel PTB domain-binding protein, NIP (Numb-interacting protein). NIP is a multipass transmembrane protein that contains two PTB domain-binding, NXXF motifs required for the interaction with Numb. In dividing Drosophila neuroblasts, NIP is colocalized to the cell membrane with Numb in a basal cortical crescent. Expression of NIP in Cos-7 cells recruited Numb from the cytosol to the plasma membrane. This recruitment of Numb to membrane by NIP was dependent on the presence of at least one NXXF site. In Drosophila Schneider 2 cells, NIP and Numb were colocalized at the plasma membrane. Inhibition of NIP expression by RNA interference released Numb to the cytosol. These results suggest that a direct protein-protein interaction between NIP and Numb is necessary and sufficient for the recruitment of Numb to the plasma membrane. Recruitment of Numb to a basal cortical crescent in a dividing neuroblast is essential for Numb to function as an intrinsic cell fate determinant.

Amino Acid Sequence↗
PubMed2005

Components of the transcriptional Mediator complex are required for asymmetric cell division in C. elegans.

Asymmetric cell division is a fundamental process that produces cellular diversity during development. In C. elegans, the Wnt signaling pathway regulates the asymmetric divisions of a number of cells including the T blast cell. We found that the let-19 and dpy-22 mutants have defects in their T-cell lineage, and lineage analyses showed that the defects were caused by disruption in the asymmetry of the T-cell division. We found that let-19 and dpy-22 encode homologs of the human proteins MED13/TRAP240 and MED12/TRAP230, respectively, which are components of the Mediator complex. Mediator is a multi-component complex that can regulate transcription by transducing the signals between activators and RNA polymerase in vitro. We also showed that LET-19 and DPY-22 form a complex in vivo with other components of Mediator, SUR-2/MED23 and LET-425/MED6. In the let-19 and dpy-22 mutants, tlp-1, which is normally expressed asymmetrically between the T-cell daughters through the function of the Wnt pathway, was expressed symmetrically in both daughter cells. Furthermore, we found that the let-19 and dpy-22 mutants were defective in the fusion of the Pn.p cell, a process that is regulated by bar-1/beta-catenin. Ectopic cell fusion in bar-1 mutants was suppressed by the let-19 or dpy-22 mutations, while defective cell fusion in let-19 mutants was suppressed by lin-39/Hox mutations, suggesting that let-19 and dpy-22 repress the transcription of lin-39. These results suggest that LET-19 and DPY-22 in the Mediator complex repress the transcription of Wnt target genes.

Amino Acid Sequence↗
PubMed1979

Role of the ftsA gene product in control of Escherichia coli cell division.

The kinetics of cell division have been studied in a strain of Escherichia coli which has an amber mutation in the ftsA gene and which also carries a temperature sensitive amber suppressor. This strain is therefore temperature sensitive for the synthesis of the ftsA protein. Cells of this strain were able to divide only if the synthesis of this protein took place during a specific part of the cell cycle. This was a short period (roughly 10 min in duration) immediately before the normal time of cell division.

Bacterial Proteins↗
PubMed1991

Neuronal determination without cell division in Xenopus embryos.

Cell division in the Xenopus CNS was blocked by incubating embryos in a mixture of the DNA synthesis inhibitors hydroxyurea and aphidicolin. Surprisingly, embryos treated at the beginning of gastrulation proceeded normally through neurulation, neural tube closure, and CNS subdivision. Thus, cell division is not critical for neural induction or early morphogenetic events in the CNS. Neuroblasts in treated embryos differentiated into neurons of many classes, indicating that cellular determination in the CNS can be dissociated from lineage and birth date. Axonal tracts and embryonic reflexes also developed. The remarkable amount of normal CNS development that occurs in these animals may be explained by a series of sequential inductions that are largely independent of cell proliferation.

Animals↗
PubMed1997

Diadenosine 5',5'''-P1,P4-tetraphosphate (Ap4A) controls the timing of cell division in Escherichia coli.

BACKGROUND: The timing of the cell division in Escherichia coli is highly regulated, but its mechanism has not been identified. Previously we have found that the cfcA1 mutation uncouples DNA replication and cell division and elevates the frequency of cell division. We further analysed the structure and the role of the cfc genes of cfcA11, a derivative of cfcA1, and another cfc mutant, cfcB1. RESULTS: The cfc mutants divided prior to the ordinary stage of cell division and produced many small cells with nucleoid. However, the cells grew exponentially, and the length of a cell cycle and the initiation mass for chromosome replication were not altered by the cfc mutations. These properties resulted from a reduction of the period between the nucleoid division and the cell division in a cell cycle, and a compensatory lengthening of the period between the cell division and the initiation of the next round of DNA replication. CfcA11 has a mutation in glySa which encodes the alpha-subunit of glycyl-tRNA synthetase, and cfcB1 has an IS2 insertion in apaH which encodes Ap4A hydrolase. The cfc properties of both cfc mutants were suppressed by a multicopy plasmid carrying apaH+, and the intracellular level of Ap4A in cfcA1 was 15-fold higher, and cfcB1 was 100-fold higher than their parent. Experiments using wild-type cells showed that a high level of Ap4A caused early cell division, and that a low level of Ap4A caused delayed cell division. CONCLUSION: Ap4A is a signal for the induction of cell division. High levels of Ap4A are responsible for the initiation of cell division. The glyS mutation permits an efficient synthesis of Ap4A.

Cell Cycle↗
PubMed2001

Roles of the fission yeast formin for3p in cell polarity, actin cable formation and symmetric cell division.

BACKGROUND: Both symmetric and asymmetric cell divisions are required for the generation of appropriate cell lineages during development. Wild-type Schizosaccharomyces pombe cells divide in a symmetric fashion to produce two similar rod-shaped daughter cells. Formins are proteins with conserved roles in cell polarity, cytokinesis, and the regulation of actin and microtubule cytoskeletons. RESULTS: Here, we identify and characterize a new S. pombe formin, for3p. for3 Delta mutant cells divide in an asymmetric manner; a mother cell divides medially to produce one daughter cell that develops into a monopolar cell and one daughter that develops into a bipolar cell. Both daughter cells recapitulate similar asymmetric lineages themselves. Inheritance of the bipolar pattern correlates with inheritance of the recent birth scar, not with asymmetry in the spindle pole bodies. for3 Delta mutants lack interphase actin cables and have delocalized actin patch and myo52p (type V myosin) distributions. for3 Delta cells have normal microtubule dynamics and cortical interactions but have defects in microtubule organization and increased numbers of microtubule bundles. for3p-GFP is localized at both cell tips in an actin-dependent manner and at the cell division site. CONCLUSIONS: for3p is a cell polarity factor required for interphase actin cable formation and microtubule organization. The for3 Delta phenotype suggests that cells are able to grow in a polarized manner even in the absence of functional actin cables and polarized distribution of actin patches. for3p and possibly actin cables are part of a regulatory network that ensures that cell divisions are symmetric.

Actins↗
PubMed1976

[The effect of extracts from Fallopian tube tissues, uterine fibromas and uterine adenocarcinomas on the growth and capacity for cell division of a human cell line].

Effects of the extracts prepared from tissues of fallopian tubes, uterine fibroid and uterine adenocarcinoma on mitotic activity and amitotic division in culture Tg33 were studied. Extracts with two protein concentrations, 25 and 100 mkg/ml, resp., were used. Differences were found between effects of extracts from malignant tissue and those of histologically unchanged fallopian tube extracts, and also the extract from tissues of uterine fibroid. The extracts from fallopian tubes removed during operation of the ovarian cyst and uterine fibroid (protein concentration 25 and 100 mkg/ml), and the extract of uterine fibroid (100 mkg/ml) caused the increase in mitotic activity. The extract from malignant tissues of adenocarcinoma (protein concentration 25 mkg/ml) and fallopian tubes (25 and 100 mkg/ml) caused no increase in the number of mitoses. The extract from tissues of uterine adenocarcinoma (protein concentration 100 mkg/ml) inhibited the number of mitoses in the culture. The above extracts effecting Tg33 cells caused the increase in the number of amitoses. The number of pathological mitoses did not increase under the influence of all the tested extracts.

Adenocarcinoma↗
PubMed1984

Adenosine inhibits cell division and promotes neurite extension in PC12 cells.

Low concentrations (10-50 microM) of adenosine (EC50 = 17 microM) or chloroadenosine (EC50 = 23 microM) prevent the division of PC12 cells. This inhibition is not mimicked by guanosine, inosine, 3',5' dideoxyadenosine, phenylisopropyladenosine, or adenylylimidodiphosphate. The growth inhibition is not relieved by addition of uridine or deoxycytidine, nor is it potentiated by homocysteine thiolactone. Inhibition of adenosine uptake does not inhibit adenosine-dependent growth arrest. PC12 variants that are deficient in adenosine kinase are as sensitive as wild-type cells to the growth-inhibitory effects of adenosine. These experiments suggest that adenosine prevents cell division at an adenosine receptor rather than acting after being metabolically altered. The adenosine receptor that inhibits cell division does not appear to be the adenosine receptor that stimulates adenylate cyclase for these reasons: (1) phenylisopropyladenosine, which is a potent agonist of this receptor, does not inhibit cell division; (2) 3',5' dideoxyadenosine does not antagonize the effect of adenosine on cell division; and (3) theophylline does not affect growth inhibition by adenosine. Thus, these experiments suggest the existence of a second adenosine receptor that can inhibit cell division. Adenosine also promotes the morphological differentiation of PC12 cells. In the presence of the adenosine deaminase inhibitor, erythro-9-(2-hydroxy-3-nonyl)adenosine (EHNA), adenosine causes the formation of short neurites (one-half to one and one-half cell diameters in length). Adenosine also increases the rate of neurite formation of both long and short neurites in response to NGF.

2-Chloroadenosine↗
PubMed1973

Process of cellular division in Escherichia coli: physiological study on thermosensitive mutants defective in cell division.

Thermosensitive fts mutants of Escherichia coli belonging to seven previously identified genetic classes (ftsA to ftsG) were studied from a physiological standpoint. These mutants immediately stopped dividing and formed multinucleated filaments when the temperature was shifted to 41 C. Macromolecular syntheses (deoxyribonucleic acid), ribonucleic acid, cell mass, and murein) continued exponentially for at least 40 to 120 min. The number of surviving bacteria remained constant during the time of incubation, and this number began to decrease exponentially, as the rate of cell mass increase leveled off from the initial rate. The recovery of cell division at 30 C in these filamentous cells was studied after 60 min of incubation at 41 C. The existence of three types of mutants was shown. The ftsA and ftsE mutants resumed cell division without new protein synthesis; ftsD mutants resumed cell division only if new protein synthesis occured, while ftsB, C, F and G mutants did not resume cell division at all. No alteration in the cell envelope was detected by the method used here, although the ftsA, B, D, F and G mutations, in contrast with ftsC and E, caused an increased resistance to penicillin G. It was also shown that the recA mutation did not suppress the effect of the fts mutations and that none of the lysogenic fts mutants induced prophage multiplication while forming filaments. The effects of osmotic pressure and salts which rescue the mutant phenotype is described.

Bacterial Proteins↗
PubMed2003

The beta-subunit of the Arabidopsis G protein negatively regulates auxin-induced cell division and affects multiple developmental processes.

Plant cells respond to low concentrations of auxin by cell expansion, and at a slightly higher concentration, these cells divide. Previous work revealed that null mutants of the alpha-subunit of a putative heterotrimeric G protein (GPA1) have reduced cell division. Here, we show that this prototypical G protein complex acts mechanistically by controlling auxin sensitivity toward cell division. Loss-of-function G protein mutants have altered auxin-mediated cell division throughout development, especially during the auxin-induced formation of lateral and adventitious root primordia. Ectopic expression of the wild-type Galpha-subunit phenocopies the Gbeta mutants (auxin hypersensitivity), probably by sequestering the Gbetagamma-subunits, whereas overexpression of Gbeta reduces auxin sensitivity and a constitutively active (Q222L) mutant Galpha behaves like the wild type. These data are consistent with a model in which Gbetagamma acts as a negative regulator of auxin-induced cell division. Accordingly, basal repression of approximately one-third of the identified auxin-regulated genes (47 of 150 upregulated genes among 8300 quantitated) is lost in the Gbeta transcript-null mutant. Included among these are genes that encode proteins proposed to control cell division in root primordia formation as well as several novel genes. These results suggest that although auxin-regulated cell division is not coupled directly by a G protein, the Gbeta-subunit attenuates this auxin pathway upstream of the control of mRNA steady state levels.

Alleles↗