Regulation of intracellular pH during the G1/S-phase transition of the neuroblastoma cell cycle

The Myb family of transcription factors is defined by homology within the DNA binding domain and includes c-Myb, A-Myb, and B-Myb. The protein products of the myb genes all bind the Myb-binding site (MBS) [YG(A/G)C(A/C/G)GTT(G/A)]. A-myb has been found to display a limited pattern of expression. Here we report that bovine aortic smooth muscle cells (SMCs) express A-myb. Sequence analysis of isolated bovine A-myb cDNA clones spanning the entire coding region indicated extensive homology with the human gene, including the putative transactivation domain. Expression of A-myb was cell cycle dependent; levels of A-myb RNA increased in the late G1-to-S phase transition following serum stimulation of serum-deprived quiescent SMC cultures and peaked in S phase. Nuclear run-on analysis revealed that an increased rate of transcription can account for most of the increase in A-myb RNA levels. Treatment of SMC cultures with 5,6-dichlorobenzimidazole riboside, a selective inhibitor of RNA polymerase II, indicated an approximate 4-h half-life for A-myb mRNA during the S phase of the cell cycle. Expression of A-myb by SMCs was stimulated by basic fibroblast growth factor, in a cell density-dependent fashion. Cotransfection of a human A-myb expression vector activated a multimerized MBS element-driven reporter construct approximately 30-fold in SMCs. The activity of c-myb and c-myc promoters, which both contain multiple MBS elements, were similarly transactivated, approximately 30- and 50-fold, respectively, upon cotransfection with human A-myb. Lastly, A-myb RNA levels could be increased by a combination of phorbol ester plus insulin-like growth factor 1. To test the role of myb family members in progression through the cell cycle, we comicroinjected c-myc and myb expression vectors into serum-deprived quiescent SMCs. The combination of c-myc and either A-myb or c-myb but not B-myb synergistically led to entry into S phase, whereas microinjection of any vector alone had little effect on S phase entry. Thus, these results suggest that A-myb is a potent transactivator in bovine SMCs and that its expression induces progression into S phase of the cell cycle.

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Ran1 functions to control the Cdc10/Sct1 complex through Puc1.

Molecular Biology of the Cell ◽

10.1091/mbc.8.6.1117 ◽

1997 ◽

Vol 8 (6) ◽

pp. 1117-1128 ◽

Cited By ~ 3

Author(s):

M Caligiuri ◽

T Connolly ◽

D Beach

Keyword(s):

Phase Transition ◽

Cell Cycle ◽

Protein Kinase ◽

Cell Fate ◽

Biochemical Analysis ◽

Control Cell ◽

S Phase ◽

Present Evidence ◽

Phosphorylation State

We have undertaken a biochemical analysis of the regulation of the G1/S-phase transition and commitment to the cell cycle in the fission yeast Schizosaccharomyces pombe. The execution of Start requires the activity of the Cdc2 protein kinase and the Sct1/Cdc10 transcription complex. Progression through G1 also requires the Ran1 protein kinase whose inactivation leads to activation of the meiotic pathway under conditions normally inhibitory to this process. We have found that in addition to Cdc2, Sct1/Cdc10 complex formation requires Ran1. We demonstrate that the Puc1 cyclin associates with Ran1 and Cdc10 in vivo and that the Ran1 protein kinase functions to control the association between Puc1 and Cdc10. In addition, we present evidence that the phosphorylation state of Cdc10 is altered upon inactivation of Ran1. These results provide biochemical evidence that demonstrate one mechanism by which the Ran1 protein kinase serves to control cell fate through Cdc10 and Puc1.

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p27kip1 controls H-Ras/MAPK activation and cell cycle entry via modulation of MT stability

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1508514112 ◽

2015 ◽

Vol 112 (45) ◽

pp. 13916-13921 ◽

Cited By ~ 36

Author(s):

Linda Fabris ◽

Stefania Berton ◽

Ilenia Pellizzari ◽

Ilenia Segatto ◽

Sara D’Andrea ◽

...

Keyword(s):

Phase Transition ◽

Cell Cycle ◽

Signaling Pathway ◽

Mapk Pathway ◽

Mapk Signaling ◽

S Phase ◽

Point Of View ◽

Cell Cycle Entry ◽

Pathway Activation ◽

Direct Binding

The cyclin-dependent kinase (CDK) inhibitor p27kip1 is a critical regulator of the G1/S-phase transition of the cell cycle and also regulates microtubule (MT) stability. This latter function is exerted by modulating the activity of stathmin, an MT-destabilizing protein, and by direct binding to MTs. We recently demonstrated that increased proliferation in p27kip1-null mice is reverted by concomitant deletion of stathmin in p27kip1/stathmin double-KO mice, suggesting that a CDK-independent function of p27kip1 contributes to the control of cell proliferation. Whether the regulation of MT stability by p27kip1 impinges on signaling pathway activation and contributes to the decision to enter the cell cycle is largely unknown. Here, we report that faster cell cycle entry of p27kip1-null cells was impaired by the concomitant deletion of stathmin. Using gene expression profiling coupled with bioinformatic analyses, we show that p27kip1 and stathmin conjunctly control activation of the MAPK pathway. From a molecular point of view, we observed that p27kip1, by controlling MT stability, impinges on H-Ras trafficking and ubiquitination levels, eventually restraining its full activation. Our study identifies a regulatory axis controlling the G1/S-phase transition, relying on the regulation of MT stability by p27kip1 and finely controlling the spatiotemporal activation of the Ras-MAPK signaling pathway.

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Retinoblastoma 1 (RB1) modulates the proliferation of chicken preadipocytes

10.1101/341453 ◽

2018 ◽

Cited By ~ 1

Author(s):

Yu-Xiang Wang ◽

Hai-Xia Wang ◽

Wei Na ◽

Fei-Yue Qin ◽

Zhi-Wei Zhang ◽

...

Keyword(s):

Gene Expression ◽

Phase Transition ◽

Cell Cycle ◽

Gene Expression Analysis ◽

Mammalian Species ◽

S Phase ◽

Pcr Analysis ◽

Quantitative Real Time Pcr ◽

Ki 67

AbstractRetinoblastoma 1 (RB1) has been extensively studied in mammalian species, but its function in avian species is unclear. The objective of this study was to reveal the role of chicken RB1 (Gallus gallus RB1, gRB1) in the proliferation of preadipocytes. In the current study, quantitative real-time PCR analysis showed that the expression levels of gRB1 transiently increased during the proliferation of preadipocytes. The MTT assay showed that gRB1 overexpression suppressed preadipocyte proliferation, and gRB1 interference promoted preadipocyte proliferation. Additionally, cell-cycle analysis indicated that gRB1 may play a crucial role in the G1/S transition. Consistently, gene expression analysis showed that gRB1 knockdown promoted marker of proliferation Ki-67 (MKi67) expression at 96 h (P < 0.05), and that overexpression of gRB1 reduced MKi67 expression at 72 h (P < 0.05). Together, our study demonstrated that gRB1 inhibited preadipocyte proliferation at least in part by inhibiting the G1 to S phase transition.

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Stimulation of Cyclin-Dependent Kinase Activity and G1- to S-Phase Transition in Human Lymphocytes by the Human T-Cell Leukemia/Lymphotropic Virus Type 1 Tax Protein

Journal of Virology ◽

10.1128/jvi.72.1.633-640.1998 ◽

1998 ◽

Vol 72 (1) ◽

pp. 633-640 ◽

Cited By ~ 89

Author(s):

Iris Schmitt ◽

Oliver Rosin ◽

Peter Rohwer ◽

Manfred Gossen ◽

Ralph Grassmann

Keyword(s):

Phase Transition ◽

Cell Cycle ◽

T Cells ◽

T Cell ◽

Virus Type ◽

S Phase ◽

T Cell Leukemia ◽

Cell Leukemia ◽

Human T Cell

ABSTRACT The human T-cell leukemia/lymphotropic virus type 1 (HTLV-1) induces a malignant lymphocytic disease. The HTLV-1 transactivator protein, Tax, is believed to be crucial for the development of the disease since it is transforming in vitro and induces tumors in transgenic animals. Although the transcriptional modulation of viral and cellular gene expression by Tax has been analyzed thoroughly, it has remained unclear how the Tax functions act on the cell cycle of primary T cells. To investigate the mechanism of Tax-mediated T-cell stimulation, we transduced primary human cord blood T cells with a conditional, tetracycline repressor-based tax expression system. Permanent Tax expression results in an abnormal proliferation of T cells which closely resemble HTLV-1-infected lymphocytes. Suppression of Tax synthesis stopped lymphocyte growth and caused cell cycle arrest in the G1 phase. Upon reinduction oftax expression, the arrested cells entered the S phase. This showed that Tax has mitogenic activity, which is required for stimulating the G1- to S-phase transition of immortalized lymphocytes. In mammalian cells, the G1-phase progression is controlled by the serial activation of several cyclin-dependent kinases (Cdks), starting with Cdk4 and Cdk6. In the presence of Tax, both Cdk4 and Cdk6 were activated. The suppression of Tax synthesis, however, resulted in a significant reduction of the Cdk4 and Cdk6 activities but did not influence the expression of Cdk4, Cdk6, or cognate D-type cyclin proteins. These data suggest that Tax induces Cdk4 and Cdk6 activity in primary human T lymphocytes; this Cdk activation is likely to account for the mitogenic Tax effect and for the abnormal T-cell proliferation of HTLV-1-infected lymphocytes.

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The RASSF1A Tumor Suppressor Restrains Anaphase-Promoting Complex/Cyclosome Activity during the G1/S Phase Transition To Promote Cell Cycle Progression in Human Epithelial Cells

Molecular and Cellular Biology ◽

10.1128/mcb.02291-07 ◽

2008 ◽

Vol 28 (10) ◽

pp. 3190-3197 ◽

Cited By ~ 19

Author(s):

Angelique W. Whitehurst ◽

Rosalyn Ram ◽

Latha Shivakumar ◽

Boning Gao ◽

John D. Minna ◽

...

Keyword(s):

Phase Transition ◽

Cell Cycle ◽

Tumor Suppressor ◽

Epithelial Cells ◽

Cyclin D1 ◽

Cell Cycle Progression ◽

S Phase ◽

Phase Cell ◽

Anaphase Promoting Complex ◽

Cycle Progression

ABSTRACT Multiple molecular lesions in human cancers directly collaborate to deregulate proliferation and suppress apoptosis to promote tumorigenesis. The candidate tumor suppressor RASSF1A is commonly inactivated in a broad spectrum of human tumors and has been implicated as a pivotal gatekeeper of cell cycle progression. However, a mechanistic account of the role of RASSF1A gene inactivation in tumor initiation is lacking. Here we have employed loss-of-function analysis in human epithelial cells for a detailed investigation of the contribution of RASSF1 to cell cycle progression. We found that RASSF1A has dual opposing regulatory connections to G1/S phase cell cycle transit. RASSF1A associates with the Ewing sarcoma breakpoint protein, EWS, to limit accumulation of cyclin D1 and restrict exit from G1. Surprisingly, we found that RASSF1A is also required to restrict SCFβTrCP activity to allow G/S phase transition. This restriction is required for accumulation of the anaphase-promoting complex/cyclosome (APC/C) inhibitor Emi1 and the concomitant block of APC/C-dependent cyclin A turnover. The consequence of this relationship is inhibition of cell cycle progression in normal epithelial cells upon RASSF1A depletion despite elevated cyclin D1 concentrations. Progression to tumorigenicity upon RASSF1A gene inactivation should therefore require collaborating genetic aberrations that bypass the consequences of impaired APC/C regulation at the G1/S phase cell cycle transition.

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Cell Cycle Control of Transcription at the G1/S Phase Transition

Cell Cycle Inhibitors in Cancer Therapy ◽

10.1385/1-59259-401-8:31 ◽

2003 ◽

pp. 31-48

Author(s):

André J. van Wijnen ◽

Gary S. Stein ◽

Janet L. Stein ◽

Jane B. Lian

Keyword(s):

Phase Transition ◽

Cell Cycle ◽

Cell Cycle Control ◽

S Phase

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E2F Is Required To Prevent Inappropriate S-Phase Entry of Mammalian Cells

Molecular and Cellular Biology ◽

10.1128/mcb.20.1.363-371.2000 ◽

2000 ◽

Vol 20 (1) ◽

pp. 363-371 ◽

Cited By ~ 24

Author(s):

Song He ◽

Brian L. Cook ◽

Benjamin E. Deverman ◽

Ulrich Weihe ◽

Fan Zhang ◽

...

Keyword(s):

Phase Transition ◽

Cell Cycle ◽

Mammalian Cells ◽

Cell Types ◽

S Phase ◽

Critical Event ◽

Cell Cycle Genes ◽

Event Triggering ◽

Critical Activity ◽

Phase Entry

ABSTRACT E2F is a family of transcription factors that regulates the cell cycle. It is widely accepted that E2F-mediated transactivation of a set of genes is the critical activity that governs cellular progression through G1 into S phase. In contrast to this hypothesis, we demonstrate that E2F actually suppresses the onset of S phase in two cell types when the cells are arrested by gamma irradiation. Our findings indicate that in these cells, the critical event triggering progression from G0/G1 arrest into S phase is the release of E2F-mediated transrepression of cell cycle genes, not transactivation by E2F. Furthermore, our data suggest that E2F-mediated transactivation is not necessary for the G1/S-phase transition in these cells.

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