scholarly journals p107 is active in the nucleolus in non-dividing human granulosa lutein cells

2000 ◽  
Vol 25 (3) ◽  
pp. 275-286 ◽  
Author(s):  
C Green ◽  
R Chatterjee ◽  
HH McGarrigle ◽  
F Ahmed ◽  
NS Thomas
Keyword(s):  
Cell Cycle ◽  
Cell Types ◽  
Quiescent State ◽  
Cdk Inhibitor ◽  
Proliferating Cells ◽  
Dividing Cells ◽  
E2f Transcription Factors ◽  
Almost All ◽  
Different Cell Types ◽  
P27 Kip1

Cells are maintained in a quiescent state by members of the retinoblastoma protein family, pRb and p130. Both are phosphoproteins and hypophosphorylated forms of pRb and p130 bind and repress the activity of E2F transcription factors, thereby preventing entry into the cell cycle. Mitogenic stimulation causes activation of cyclin dependent kinases (cdk) that phosphorylate both pRb and p130, thereby releasing E2F factors which stimulate the transcription of a number of genes that are required for DNA synthesis and for regulating the cell cycle. In non-dividing cells, cdks are maintained in an inactive state by cdk inhibitor proteins such as p27(Kip1). The aim of our study was to determine how E2F complexes are regulated during the differentiation of human primary granulosa lutein cells (GLC) of the corpus luteum (CL). The CL is formed in the ovary after ovulation at the terminal stage of folliculogenesis after completion of maturation and differentiation of Graafian follicles. As shown by flow cytometry GLC are not dividing, being predominantly in the G(0)/G(1) phase of the cell cycle and, consistent with this, they contain the cdk inhibitor protein, p27(Kip1), but not E2F-1 which is normally expressed only in proliferating cells. The GLC do express E2F-4, hypophosphorylated pRb, p130 forms 1 and 2 and, surprisingly, hypophosphorylated p107. p107 is normally present only in dividing cells where it regulates E2F activity during the cell cycle. These forms of pRb, p130 as well as p107, together with E2F-4 are all active in that they can bind an E2F DNA-binding site in a pull-down assay. Immunocytochemistry shows that these proteins are expressed in almost all GLC but have different sub-cellular distribution: p107 is concentrated in nucleoli, while p130 and E2F-4 show relatively even nuclear and cytoplasmic distributions. Both pRb and p130 have been implicated previously in repressing E2F activity in many different cell types during cell cycle arrest in G(0)/G(1). We conclude that p107 is active in human primary GLC but its nucleolar localisation would suggest that it represses ribosomal RNA synthesis rather than E2F activity.

scholarly journals A computational model of mitochondrial deoxynucleotide metabolism and DNA replication

2005 ◽  
Vol 288 (5) ◽  
pp. C989-C1002 ◽  
Author(s):  
Patrick C. Bradshaw ◽  
David C. Samuels
Keyword(s):  
Computational Model ◽  
Cell Types ◽  
Matrix Space ◽  
Previous Hypothesis ◽  
Postmitotic Cells ◽  
Dividing Cells ◽  
Mtdna Replication ◽  
Time Required ◽  
Almost All ◽  
Different Cell Types

We present a computational model of mitochondrial deoxynucleotide metabolism and mitochondrial DNA (mtDNA) synthesis. The model includes the transport of deoxynucleosides and deoxynucleotides into the mitochondrial matrix space, as well as their phosphorylation and polymerization into mtDNA. Different simulated cell types (cancer, rapidly dividing, slowly dividing, and postmitotic cells) are represented in this model by different cytoplasmic deoxynucleotide concentrations. We calculated the changes in deoxynucleotide concentrations within the mitochondrion during the course of a mtDNA replication event and the time required for mtDNA replication in the different cell types. On the basis of the model, we define three steady states of mitochondrial deoxynucleotide metabolism: the phosphorylating state (the net import of deoxynucleosides and export of phosphorylated deoxynucleotides), the desphosphorylating state (the reverse of the phosphorylating state), and the efficient state (the net import of both deoxynucleosides and deoxynucleotides). We present five testable hypotheses based on this simulation. First, the deoxynucleotide pools within a mitochondrion are sufficient to support only a small fraction of even a single mtDNA replication event. Second, the mtDNA replication time in postmitotic cells is much longer than that in rapidly dividing cells. Third, mitochondria in dividing cells are net sinks of cytoplasmic deoxynucleotides, while mitochondria in postmitotic cells are net sources. Fourth, the deoxynucleotide carrier exerts the most control over the mtDNA replication rate in rapidly dividing cells, but in postmitotic cells, the NDPK and TK2 enzymes have the most control. Fifth, following from the previous hypothesis, rapidly dividing cells derive almost all of their mtDNA precursors from the cytoplasmic deoxynucleotides, not from phosphorylation within the mitochondrion.

scholarly journals Therapeutic Exosomes in Prognosis and Developments of Coronary Artery Disease

2021 ◽  
Vol 8 ◽  
Author(s):  
Ai-Qun Chen ◽  
Xiao-Fei Gao ◽  
Zhi-Mei Wang ◽  
Feng Wang ◽  
Shuai Luo ◽  
...  
Keyword(s):  
Coronary Artery Disease ◽  
Coronary Artery ◽  
Cell Types ◽  
Biological Functions ◽  
Stent Restenosis ◽  
Artery Disease ◽  
Almost All ◽  
Different Cell Types ◽  
Insight Into ◽  
Systematic Knowledge

Exosomes, with an diameter of 30~150 nm, could be released from almost all types of cells, which contain diverse effective constituent, such as RNAs, proteins, lipids, and so on. In recent years, exosomes have been verified to play an important role in mechanism, diagnosis, treatment, and prognosis of cardiovascular disease, especially coronary artery disease (CAD). Moreover, it has also been shown that exosomes derived from different cell types have various biological functions based on the cell stimulation and microenvironment. However, therapeutic exosomes are currently far away from clinical translation, despite it is full of hope. In this review, we summarize an update of the recent studies and systematic knowledge of therapeutic exosomes in atherosclerosis, myocardial infarction, and in-stent restenosis, which might provide a novel insight into the treatment of CAD and promote the potential clinical application of therapeutic exosomes.

Paralogs of Atlantic salmon myoblast determination factor genes are distinctly regulated in proliferating and differentiating myogenic cells

2010 ◽  
Vol 298 (6) ◽  
pp. R1615-R1626 ◽  
Author(s):  
Neil I. Bower ◽  
Ian A. Johnston
Keyword(s):  
Cell Cycle ◽  
Amino Acids ◽  
Amino Acid ◽  
Atlantic Salmon ◽  
Antigen Expression ◽  
Nuclear Antigen ◽  
Quiescent State ◽  
Mrna Levels ◽  
Proliferating Cells

The mRNA expression of myogenic regulatory factors, including myoD1 (myoblast determination factor) gene paralogs, and their regulation by amino acids and insulin-like growth factors were investigated in primary cell cultures isolated from fast myotomal muscle of Atlantic salmon ( Salmo salar). The cell cycle and S phase were determined as 28.1 and 13.3 h, respectively, at 18°C. Expression of myoD1b and myoD1c peaked at 8 days of culture in the initial proliferation phase and then declined more than sixfold as cells differentiated and was correlated with PCNA (proliferating cell nuclear antigen) expression ( R = 0.88, P < 0.0001; R = 0.70, P < 0.0001). In contrast, myoD1a transcripts increased from 2 to 8 days and remained at elevated levels as myotubes were formed. mRNA levels of myoD1c were, on average, 3.1- and 5.7-fold higher than myoD1a and myoD1b, respectively. Depriving cells of amino acids and serum led to a rapid increase in pax7 and a decrease in myoD1c and PCNA expression, indicating a transition to a quiescent state. In contrast, amino acid replacement in starved cells produced significant increases in myoD1c (at 6 h), PCNA (at 12 h), and myoD1b (at 24 h) and decreases in pax7 expression as cells entered the cell cycle. Our results are consistent with temporally distinct patterns of myoD1c and myoD1b expression at the G1 and S/G2 phases of the cell cycle. Treatment of starved cells with insulin-like growth factor I or II did not alter expression of the myoD paralogs. It was concluded that, in vitro, amino acids alone are sufficient to stimulate expression of genes regulating myogenesis in myoblasts involving autocrine/paracrine pathways. The differential responses of myoD paralogs during myotube maturation and amino acid treatments suggest that myoD1b and myoD1c are primarily expressed in proliferating cells and myoD1a in differentiating cells, providing evidence for their subfunctionalization following whole genome and local duplications in the Atlantic salmon lineage.

scholarly journals CA Mutation N57A Has Distinct Strain-Specific HIV-1 Capsid Uncoating and Infectivity Phenotypes

2019 ◽  
Vol 93 (9) ◽  
Author(s):  
Douglas K. Fischer ◽  
Akatsuki Saito ◽  
Christopher Kline ◽  
Romy Cohen ◽  
Simon C. Watkins ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Amino Acid ◽  
Cell Types ◽  
Careful Consideration ◽  
Immunodeficiency Virus ◽  
Cell Cycle Dependence ◽  
Cycle Dependent ◽  
Multiple Strains ◽  
Different Cell Types ◽  
Hiv 1

ABSTRACTThe ability of human immunodeficiency virus type 1 (HIV-1) to transduce nondividing cells is key to infecting terminally differentiated macrophages, which can serve as a long-term reservoir of HIV-1 infection. The mutation N57A in the viral CA protein renders HIV-1 cell cycle dependent, allowing examination of HIV-1 infection of nondividing cells. Here, we show that the N57A mutation confers a postentry infectivity defect that significantly differs in magnitude between the common lab-adapted molecular clones HIV-1NL4-3(>10-fold) and HIV-1LAI(2- to 5-fold) in multiple human cell lines and primary CD4+T cells. Capsid permeabilization and reverse transcription are altered when N57A is incorporated into HIV-1NL4-3but not HIV-1LAI. The N57A infectivity defect is significantly exacerbated in both virus strains in the presence of cyclosporine (CsA), indicating that N57A infectivity is dependent upon CA interacting with host factor cyclophilin A (CypA). Adaptation of N57A HIV-1LAIselected for a second CA mutation, G94D, which rescued the N57A infectivity defect in HIV-1LAIbut not HIV-1NL4-3. The rescue of N57A by G94D in HIV-1LAIis abrogated by CsA treatment in some cell types, demonstrating that this rescue is CypA dependent. An examination of over 40,000 HIV-1 CA sequences revealed that the four amino acids that differ between HIV-1NL4-3and HIV-1LAICA are polymorphic, and the residues at these positions in the two strains are widely prevalent in clinical isolates. Overall, a few polymorphic amino acid differences between two closely related HIV-1 molecular clones affect the phenotype of capsid mutants in different cell types.IMPORTANCEThe specific mechanisms by which HIV-1 infects nondividing cells are unclear. A mutation in the HIV-1 capsid protein abolishes the ability of the virus to infect nondividing cells, serving as a tool to examine cell cycle dependence of HIV-1 infection. We have shown that two widely used HIV-1 molecular clones exhibit significantly different N57A infectivity phenotypes due to fewer than a handful of CA amino acid differences and that these clones are both represented in HIV-infected individuals. As such minor differences in closely related HIV-1 strains may impart significant infectivity differences, careful consideration should be given to drawing conclusions from one particular HIV-1 clone. This study highlights the potential for significant variation in results with the use of multiple strains and possible unanticipated effects of natural polymorphisms.

scholarly journals Antiproliferative Effect of Dihydroxyacetone on Trypanosoma brucei Bloodstream Forms: Cell Cycle Progression, Subcellular Alterations, and Cell Death

2007 ◽  
Vol 51 (11) ◽  
pp. 3960-3968 ◽  
Author(s):  
Néstor L. Uzcátegui ◽  
Didac Carmona-Gutiérrez ◽  
Viola Denninger ◽  
Caroline Schoenfeld ◽  
Florian Lang ◽  
...  
Keyword(s):  
Energy Source ◽  
Cell Cycle ◽  
Trypanosoma Brucei ◽  
Rational Design ◽  
Cell Cycle Progression ◽  
Cell Types ◽  
Cycle Arrest ◽  
Starting Point ◽  
M Phase ◽  
Different Cell Types

ABSTRACT We evaluated the effects of dihydroxyacetone (DHA) on Trypanosoma brucei bloodstream forms. DHA is considered an energy source for many different cell types. T. brucei takes up DHA readily due to the presence of aquaglyceroporins. However, the parasite is unable to use it as a carbon source because of the absence of DHA kinase (DHAK). We could not find a homolog of the relevant gene in the genomic database of T. brucei and have been unable to detect DHAK activity in cell lysates of the parasite, and the parasite died quickly if DHA was the sole energy source in the medium. In addition, during trypanosome cultivation, DHA induced growth inhibition with a 50% inhibitory concentration of about 1 mM, a concentration that is completely innocuous to mammals. DHA caused cell cycle arrest in the G2/M phase of up to 70% at a concentration of 2 mM. Also, DHA-treated parasites showed profound ultrastructural alterations, including an increase of vesicular structures within the cytosol and the presence of multivesicular bodies, myelin-like structures, and autophagy-like vacuoles, as well as a marked disorder of the characteristic mitochondrion structure. Based on the toxicity of DHA for trypanosomes compared with mammals, we consider DHA a starting point for a rational design of new trypanocidal drugs.

scholarly journals Density-dependent Growth Inhibition of Fibroblasts Ectopically Expressing p27kip1

2000 ◽  
Vol 11 (6) ◽  
pp. 2117-2130 ◽  
Author(s):  
Xiaohong Zhang ◽  
Walker Wharton ◽  
Marcia Donovan ◽  
Domenico Coppola ◽  
Rhonda Croxton ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Density ◽  
Ectopic Expression ◽  
High Density ◽  
Quiescent State ◽  
Low Density ◽  
Cdk Inhibitor ◽  
Cyclin Dependent Kinase ◽  
Tumor Virus ◽  
Dependent Growth

The cyclin/cyclin-dependent kinase (cdk) inhibitor p27kip1 is thought to be responsible for the onset and maintenance of the quiescent state. It is possible, however, that cells respond differently to p27kip1 in different conditions, and using a BALB/c-3T3 cell line (termed p27-47) that inducibly expresses high levels of this protein, we show that the effect of p27kip1 on cell cycle traverse is determined by cell density. We found that ectopic expression of p27kip1blocked the proliferation of p27-47 cells at high density but had little effect on the growth of cells at low density whether exponentially cycling or stimulated from quiescence. Regardless of cell density, the activities of cdk4 and cdk2 were markedly repressed by p27kip1 expression, as was the cdk4-dependent dissociation of E2F4/p130 complexes. Infection of cells with SV40, a DNA tumor virus known to abrogate formation of p130- and Rb-containing complexes, allowed dense cultures to proliferate in the presence of supraphysiological amounts of p27kip1 but did not stimulate cell cycle traverse when cultures were cotreated with the potent cdk2 inhibitor roscovitine. Our data suggest that residual levels of cyclin/cdk activity persist in p27kip1-expressing p27-47 cells and are sufficient for the growth of low-density cells and of high-density cells infected with SV40, and that effective disruption of p130 and/or Rb complexes is obligatory for the proliferation of high-density cultures.

scholarly journals Plk4 triggers autonomous de novo centriole biogenesis and maturation

2021 ◽  
Vol 220 (5) ◽  
Author(s):  
Catarina Nabais ◽  
Delphine Pessoa ◽  
Jorge de-Carvalho ◽  
Thomas van Zanten ◽  
Paulo Duarte ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
De Novo ◽  
Cell Types ◽  
Proliferating Cells ◽  
Cycle Progression ◽  
Controlled System ◽  
Pericentriolar Material ◽  
Centriole Assembly ◽  
Critical Components

Centrioles form centrosomes and cilia. In most proliferating cells, centrioles assemble through canonical duplication, which is spatially, temporally, and numerically regulated by the cell cycle and the presence of mature centrioles. However, in certain cell types, centrioles assemble de novo, yet by poorly understood mechanisms. Herein, we established a controlled system to investigate de novo centriole biogenesis, using Drosophila melanogaster egg explants overexpressing Polo-like kinase 4 (Plk4), a trigger for centriole biogenesis. We show that at a high Plk4 concentration, centrioles form de novo, mature, and duplicate, independently of cell cycle progression and of the presence of other centrioles. Plk4 concentration determines the temporal onset of centriole assembly. Moreover, our results suggest that distinct biochemical kinetics regulate de novo and canonical biogenesis. Finally, we investigated which other factors modulate de novo centriole assembly and found that proteins of the pericentriolar material (PCM), and in particular γ-tubulin, promote biogenesis, likely by locally concentrating critical components.

scholarly journals Cell Cycle Control of a Holdfast Attachment Gene inCaulobacter crescentus

1999 ◽  
Vol 181 (4) ◽  
pp. 1118-1125 ◽  
Author(s):  
Raji S. Janakiraman ◽  
Yves V. Brun
Keyword(s):  
Cell Cycle ◽  
Polar Region ◽  
Caulobacter Crescentus ◽  
Cell Cycle Control ◽  
Indirect Evidence ◽  
Cell Types ◽  
Transmission Electron ◽  
Different Cell Types ◽  
Prosthecate Bacterium ◽  
Maximal Expression

ABSTRACT Attachment to surfaces by the prosthecate bacteriumCaulobacter crescentus is mediated by an adhesive organelle, the holdfast, found at the tip of the stalk. Indirect evidence suggested that the holdfast first appears at the swarmer pole of the predivisional cell. We used fluorescently labeled lectin and transmission electron microscopy to detect the holdfast in different cell types. While the holdfast was readily detectable in stalked cells and at the stalked poles of predivisional cells, we were unable to detect the holdfast in swarmer cells or at the flagellated poles of predivisional cells. This suggests that exposure of the holdfast to the outside of the cell occurs during the differentiation of swarmer to stalked cells. To investigate the timing of holdfast synthesis and exposure to the outside of the cell, we have examined the regulation of a holdfast attachment gene, hfaA. The hfaA gene is part of a cluster of four genes (hfaABDC), identified in strain CB2A and involved in attachment of the holdfast to the polar region of the cell. We have identified the hfaA gene in the synchronizable C. crescentus strain CB15. The sequence of the CB2A hfaA promoter suggested that it was regulated by ς54. We show that the transcription of hfaAfrom either strain is not dependent on ς54. Using ahfaA-lacZ fusion, we show that the transcription ofhfaA is temporally regulated during the cell cycle, with maximal expression in late-predivisional cells. This increase in expression is largely due to the preferential transcription ofhfaA in the swarmer pole of the predivisional cell.

Environmental control of the cell cycle in Drosophila: nutrition activates mitotic and endoreplicative cells by distinct mechanisms

Development ◽  
1998 ◽  
Vol 125 (11) ◽  
pp. 2149-2158 ◽  
Author(s):  
J.S. Britton ◽  
B.A. Edgar
Keyword(s):  
Cell Cycle ◽  
Fat Body ◽  
Environmental Control ◽  
Ectopic Expression ◽  
Cell Types ◽  
Quiescent State ◽  
Independent Manner ◽  
Cell Cycle Activation ◽  
E2f Transcription Factor

In newly hatched Drosophila larvae, quiescent cells reenter the cell cycle in response to dietary amino acids. To understand this process, we varied larval nutrition and monitored effects on cell cycle initiation and maintenance in the mitotic neuroblasts and imaginal disc cells, as well as the endoreplicating cells in other larval tissues. After cell cycle activation, mitotic and endoreplicating cells respond differently to the withdrawal of nutrition: mitotic cells continue to proliferate in a nutrition-independent manner, while most endoreplicating cells reenter a quiescent state. We also show that ectopic expression of Drosophila Cyclin E or the E2F transcription factor can drive quiescent endoreplicating cells, but not quiescent imaginal neuroblasts, into S-phase. Conversely, we demonstrate that quiescent imaginal neuroblasts, but not quiescent endoreplicating cells, can be induced to enter the cell cycle when co-cultured with larval fat body in vitro. These results demonstrate a fundamental difference in the control of cell cycle activation and maintenance in these two cell types, and imply the existence of a novel mitogen generated by the larval fat body in response to nutrition.

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