scholarly journals Increased Expression of Cyclin D2 during Multiple States of Growth Arrest in Primary and Established Cells

1998 ◽  
Vol 18 (6) ◽  
pp. 3163-3172 ◽  
Author(s):  
Muthupalaniappan Meyyappan ◽  
Howard Wong ◽  
Christopher Hull ◽  
Karl T. Riabowol
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Growth Arrest ◽  
Growth Conditions ◽  
Cellular Growth ◽  
Serum Starvation ◽  
Cyclin D2 ◽  
Cycle Progression ◽  
Quiescent Cells ◽  
D2 Protein

ABSTRACT Cyclin D2 is a member of the family of D-type cyclins that is implicated in cell cycle regulation, differentiation, and oncogenic transformation. To better understand the role of this cyclin in the control of cell proliferation, cyclin D2 expression was monitored under various growth conditions in primary human and established murine fibroblasts. In different states of cellular growth arrest initiated by contact inhibition, serum starvation, or cellular senescence, marked increases (5- to 20-fold) were seen in the expression levels of cyclin D2 mRNA and protein. Indirect immunofluorescence studies showed that cyclin D2 protein localized to the nucleus in G0, suggesting a nuclear function for cyclin D2 in quiescent cells. Cyclin D2 was also found to be associated with the cyclin-dependent kinases CDK2 and CDK4 but not CDK6 during growth arrest. Cyclin D2-CDK2 complexes increased in amounts but were inactive as histone H1 kinases in quiescent cells. Transient transfection and needle microinjection of cyclin D2 expression constructs demonstrated that overexpression of cyclin D2 protein efficiently inhibited cell cycle progression and DNA synthesis. These data suggest that in addition to a role in promoting cell cycle progression through phosphorylation of retinoblastoma family proteins in some cell systems, cyclin D2 may contribute to the induction and/or maintenance of a nonproliferative state, possibly through sequestration of the CDK2 catalytic subunit.

scholarly journals Heat shock protein 27 promotes cell cycle progression by down-regulating E2F transcription factor 4 and retinoblastoma family protein p130

2018 ◽  
Vol 293 (41) ◽  
pp. 15815-15826 ◽  
Author(s):  
Ah-Mee Park ◽  
Ikuo Tsunoda ◽  
Osamu Yoshie
Keyword(s):  
Cell Cycle ◽  
Heat Shock ◽  
Heat Shock Protein ◽  
Cellular Senescence ◽  
Cell Cycle Progression ◽  
Heat Shock Protein 27 ◽  
Serum Starvation ◽  
Cell Cycle Gene ◽  
Cycle Progression ◽  
Human Lung Fibroblast

Heat shock protein 27 (HSP27) protects cells under stress. Here, we demonstrate that HSP27 also promotes cell cycle progression of MRC-5 human lung fibroblast cells. Serum starvation for 24 h induced G1 arrest in these cells, and upon serum refeeding, the cells initiated cell cycle progression accompanied by an increase in HSP27 protein levels. HSP27 levels peaked at 12 h, and transcriptional up-regulation of six G2/M-related genes (CCNA2, CCNB1, CCNB2, CDC25C, CDCA3, and CDK1) peaked at 24–48 h. siRNA-mediated HSP27 silencing in proliferating MRC-5 cells induced G2 arrest coinciding with down-regulation of these six genes. Of note, the promoters of all of these genes have the cell cycle–dependent element and/or the cell cycle gene-homology region. These promoter regions are known to be bound by the E2F family proteins (E2F-1 to E2F-8) and retinoblastoma (RB) family proteins (RB1, p107, and p130), among which E2F-4 and p130 were strongly up-regulated in HSP27-knockdown cells. E2F-4 or p130 knockdown concomitant with the HSP27 knockdown rescued MRC-5 cells from G2 arrest and up-regulated the six cell cycle genes. Moreover, we observed cellular senescence in MRC-5 cells on day 3 after the HSP27 knockdown, as evidenced by increased senescence-associated β-gal activity and up-regulated inflammatory cytokines. The cellular senescence was also suppressed by the concomitant knockdown of E2F-4/HSP27 or p130/HSP27. Our findings indicate that HSP27 promotes cell cycle progression of MRC-5 cells by suppressing expression of the transcriptional repressors E2F-4 and p130.

scholarly journals A novel form of Deleted in breast cancer 1 (DBC1) lacking the N-terminal domain does not bind SIRT1 and is dynamically regulated in vivo

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Leonardo Santos ◽  
Laura Colman ◽  
Paola Contreras ◽  
Claudia C. Chini ◽  
Adriana Carlomagno ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cell Cycle ◽  
Liver Regeneration ◽  
Partial Hepatectomy ◽  
Normal Cell ◽  
Cell Cycle Progression ◽  
Cycle Progression ◽  
Quiescent Cells ◽  
Normal Cell Cycle

Abstract The protein Deleted in Breast Cancer-1 is a regulator of several transcription factors and epigenetic regulators, including HDAC3, Rev-erb-alpha, PARP1 and SIRT1. It is well known that DBC1 regulates its targets, including SIRT1, by protein-protein interaction. However, little is known about how DBC1 biological activity is regulated. In this work, we show that in quiescent cells DBC1 is proteolytically cleaved, producing a protein (DN-DBC1) that misses the S1-like domain and no longer binds to SIRT1. DN-DBC1 is also found in vivo in mouse and human tissues. Interestingly, DN-DBC1 is cleared once quiescent cells re-enter to the cell cycle. Using a model of liver regeneration after partial hepatectomy, we found that DN-DBC1 is down-regulated in vivo during regeneration. In fact, WT mice show a decrease in SIRT1 activity during liver regeneration, coincidentally with DN-DBC1 downregulation and the appearance of full length DBC1. This effect on SIRT1 activity was not observed in DBC1 KO mice. Finally, we found that DBC1 KO mice have altered cell cycle progression and liver regeneration after partial hepatectomy, suggesting that DBC1/DN-DBC1 transitions play a role in normal cell cycle progression in vivo after cells leave quiescence. We propose that quiescent cells express DN-DBC1, which either replaces or coexist with the full-length protein, and that restoring of DBC1 is required for normal cell cycle progression in vitro and in vivo. Our results describe for the first time in vivo a naturally occurring form of DBC1, which does not bind SIRT1 and is dynamically regulated, thus contributing to redefine the knowledge about its function.

Truncation in CCND1 mRNA 3′ UTR Is Associated with An Aggressive Phenotype and Chemoresistance

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 5287-5287
Author(s):  
Robert W Chen ◽  
Myo Htut ◽  
Britta Hoehn ◽  
Eamon Berge ◽  
William Robinson ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Protein Expression ◽  
Cyclin D1 ◽  
Cell Lines ◽  
Cell Cycle Progression ◽  
Serum Starvation ◽  
Cycle Progression ◽  
Serum Free ◽  
Aggressive Phenotype ◽  
Free Media

Abstract Mantle Cell Lymphoma (MCL) represents 5–10% of all non-Hodgkins lymphomas, making it an uncommon but difficult form of lymphoma to treat. It has the worst prognosis among the B cell lymphomas with median survival of three years. The genetic hallmark of MCL is the t(11,14)(q13;32) translocation causing amplification of cyclin D1 (CCND1). It is a well known cell cycle regulator. Multiple reports have shown a truncation in the cyclin D1 mRNA 3′ untranslated region. This truncation increases CCND1 protein expression by not only enhancing the half-life of CCND1 mRNA, but also evades microRNA regulation of mRNA translation. The dramatic overexpression of CCND1 mRNA and protein has been associated to poor clinical outcome in patients. We hypothesize that this truncation leads to a more aggressive phenotype and induces chemoresistance in MCL. We have identified 4 MCL cell lines (Granta-519, JVM-2, Jeko-1, and Z138) with different levels of the truncated CCND1 mRNA. We were able to show that Z138 and Jeko-1 have a much higher ratio of truncated CCND1 mRNA to the full length CCND1 mRNA as compared to Granta-519 and JVM-2. We were also able to show that this truncated mRNA leads to an increase in CCND1 protein expression. By using flow cytometry, we correlated the increase in CCND1 protein expression to faster cell cycle progression. We proposed that cell lines with increased CCND1 expression are phenotypically more aggressive, and would be able to continue cell cycle progression without serum support. We were able to arrest JVM-2 in G1 phase after 48 hours of serum starvation. However, we were not able to arrest cell cycle progression in Jeko-1 even after 96 hours of serum starvation. Western blot analysis shows that CCND1 protein expression is decreased in JVM-2 but remains unchanged in Jeko-1 with serum starvation. The same phenomenon was observed in Granta-519 and Z138. The MCL cell lines (Jeko-1 and Z-138) with more CCND1 protein expression were able to continue cell cycle progression in serum free media. The MCL cell lines (JVM-2 and Granta-519) with less CCND1 protein expression were not able to continue cell cycle progression in serum free media. This shows that CCND1 overexpression is associated with a more aggressive phenotype. We then treated the 4 MCL cell lines with varying concentrations of doxorubicin, a standard anthracycline chemotherapy used in the treatment of MCL patients. We used MTS assay to assess cell proliferation after treatment with doxorubicin. We found the IC 50 (inhibitory concentration 50%) of doxorubicin in these cell lines varied from 6nM to 600nM. The cell lines (Jeko-1 and Z-138) with more CCND1 protein expression have a much higher IC 50 as compared to the cell lines (JVM-2 and Granta-519) with less CCND1 protein expression. This demonstrates that CCND1 overexpression is associated with chemoresistance. We conclude truncation in CCND1 mRNA leads to increased CCND1 protein expression and faster cell cycle progression CCND1 overexpression is associated with an aggressive phenotype CCND1 overexpression is associated with chemoresistance.

scholarly journals Lamina-associated polypeptide 2α regulates cell cycle progression and differentiation via the retinoblastoma–E2F pathway

2006 ◽  
Vol 173 (1) ◽  
pp. 83-93 ◽  
Author(s):  
Daniela Dorner ◽  
Sylvia Vlcek ◽  
Nicole Foeger ◽  
Andreas Gajewski ◽  
Christian Makolm ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Target Genes ◽  
Serum Starvation ◽  
Dependent Manner ◽  
Cycle Progression ◽  
Promoter Sequences ◽  
Delayed Entry ◽  
Accelerated Proliferation

Lamina-associated polypeptide (LAP) 2α is a nonmembrane-bound LAP2 isoform that forms complexes with nucleoplasmic A-type lamins. In this study, we show that the overexpression of LAP2α in fibroblasts reduced proliferation and delayed entry into the cell cycle from a G0 arrest. In contrast, stable down-regulation of LAP2α by RNA interference accelerated proliferation and interfered with cell cycle exit upon serum starvation. The LAP2α-linked cell cycle phenotype is mediated by the retinoblastoma (Rb) protein because the LAP2α COOH terminus directly bound Rb, and overexpressed LAP2α inhibited E2F/Rb-dependent reporter gene activity in G1 phase in an Rb-dependent manner. Furthermore, LAP2α associated with promoter sequences in endogenous E2F/Rb-dependent target genes in vivo and negatively affected their expression. In addition, the expression of LAP2α in proliferating preadipocytes caused the accumulation of hypophosphorylated Rb, which is reminiscent of noncycling cells, and initiated partial differentiation into adipocytes. The effects of LAP2α on cell cycle progression and differentiation may be highly relevant for the cell- and tissue-specific phenotypes observed in laminopathic diseases.

scholarly journals p73 and p63 Sustain Cellular Growth by Transcriptional Activation of Cell Cycle Progression Genes

2009 ◽  
Vol 69 (22) ◽  
pp. 8563-8571 ◽  
Author(s):  
K. Lefkimmiatis ◽  
M. F. Caratozzolo ◽  
P. Merlo ◽  
A. M. D'Erchia ◽  
B. Navarro ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Transcriptional Activation ◽  
Cell Cycle Progression ◽  
Cellular Growth ◽  
Cycle Progression

scholarly journals Inhibition of p53-mediated growth arrest by overexpression of cyclin-dependent kinases.

1996 ◽  
Vol 16 (8) ◽  
pp. 4445-4455 ◽  
Author(s):  
K M Latham ◽  
S W Eastman ◽  
A Wong ◽  
P W Hinds
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Growth Arrest ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Aberrant Expression ◽  
Cycle Progression ◽  
Cyclin Dependent Kinases ◽  
Rat Fibroblasts ◽  
Wild Type P53

Rat fibroblasts transformed by a temperature-sensitive mutant of murine p53 undergo a reversible growth arrest in G1 at 32.5 degrees C, the temperature at which p53 adopts a wild-type conformation. The arrested cells contain inactive cyclin-dependent kinase 2 (cdk2) despite the presence of high levels of cyclin E and cdk-activating kinase activity. This is due in part to p53-dependent expression of the p2l cdk inhibitor. Upon shift to 39 degrees C, wild-type p53 is lost and cdk2 activation and pRb phosphorylation occur concomitantly with loss of p2l. This p53-mediated growth arrest can be abrogated by overexpression of cdk4 and cdk6 but not cdk2 or cyclins, leading to continuous proliferation of transfected cells in the presence of wild-type p53 and p2l. Kinase-inactive counterparts of cdk4 and cdk6 also rescue these cells from growth arrest, implicating a noncatalytic role for cdk4 and cdk6 in this resistance to p53-mediated growth arrest. Aberrant expression of these cell cycle kinases may thus result in an oncogenic interference with inhibitors of cell cycle progression.

scholarly journals EPO modulation of cell-cycle regulatory genes, and cell division, in primary bone marrow erythroblasts

Blood ◽  
2007 ◽  
Vol 110 (7) ◽  
pp. 2361-2370 ◽  
Author(s):  
Jing Fang ◽  
Madhu Menon ◽  
William Kapelle ◽  
Olga Bogacheva ◽  
Oleg Bogachev ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Bone Marrow ◽  
Cell Cycle Progression ◽  
S Phase ◽  
Regulatory Genes ◽  
Primary System ◽  
Cyclin D2 ◽  
Cycle Progression ◽  
Cyclin G2 ◽  
Cell Cycle Regulatory Genes

Erythropoietin (EPO's) actions on erythroblasts are ascribed largely to survival effects. Certain studies, however, point to EPO-regulated proliferation. To investigate this problem in a primary system, KitposCD71high erythroblasts were prepared from murine bone marrow, and were first used in the array-based discovery of EPO-modulated cell-cycle regulators. Five cell-cycle progression factors were rapidly up-modulated: nuclear protein 1 (Nupr1), G1 to S phase transition 1 (Gspt1), early growth response 1 (Egr1), Ngfi-A binding protein 2 (Nab2), and cyclin D2. In contrast, inhibitory cyclin G2, p27/Cdkn1b, and B-cell leukemia/lymphoma 6 (Bcl6) were sharply down-modulated. For CYCLIN G2, ectopic expression also proved to selectively attenuate EPO-dependent UT7epo cell-cycle progression at S-phase. As analyzed in primary erythroblasts expressing minimal EPO receptor alleles, EPO repression of cyclin G2 and Bcl6, and induction of cyclin D2, were determined to depend on PY343 (and Stat5) signals. Furthermore, erythroblasts expressing a on PY-null EPOR-HM allele were abnormally distributed in G0/G1. During differentiation divisions, EPOR-HM Ter119pos erythroblasts conversely accumulated in S-phase and faltered in an apparent EPO-directed transition to G0/G1. EPO/EPOR signals therefore control the expression of select cell-cycle regulatory genes that are proposed to modulate stage-specific decisions for erythroblast cell-cycle progression.

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