Human lactoferrin controls the level of retinoblastoma protein and its activityThis paper is one of a selection of papers published in this Special Issue, entitled 7th International Conference on Lactoferrin: Structure, Function, and Applications, and has undergone the Journal's usual peer review process.

2006 ◽  
Vol 84 (3) ◽  
pp. 345-350 ◽  
Author(s):  
Hee-Joung Son ◽  
Shin-Hee Lee ◽  
Sang-Yun Choi
Keyword(s):  
Cell Cycle ◽  
Cell Growth ◽  
Kinase Inhibitor ◽  
Peer Review Process ◽  
Cell Cycle Control ◽  
Retinoblastoma Protein ◽  
Cyclin Dependent Kinase ◽  
Antiproliferative Effects ◽  
Cyclin Dependent Kinase Inhibitor ◽  
Selection Of

Lactoferrin (Lf) has been implicated in the regulation of cell growth. However, the molecular mechanism underlying this effect remains to be elucidated. In this study, we show that Lf is involved in the cell cycle control system in a variety of cell lines, through retinoblastoma protein (Rb) - mediated growth arrest. We observed that Lf induces the expression of Rb, a signal mediator of cell cycle control, and that a majority of this Lf-induced Rb persists in a hypophosphorylated form. In addition, we determined that Lf specifically augments the level of a cyclin-dependent kinase inhibitor, p21, but not p27. Upon treatment with Lf, H1299 cells expressing defective p53 effected an augmentation of endogenous p21 levels, which may contribute to the accumulation of hypophosphorylated Rb. A substantial quantity of active Rb binds more efficiently to E2F1 in cells that express Lf and consequently blocks the expression of an E2F1-responsive gene, thereby suggesting that Lf plays a crucial role in the inhibition of tumor cell growth. Therefore, we conclude that the antiproliferative effects of Lf can likely be attributed to the elevated levels of hypophosphorylated Rb.

scholarly journals Down-Regulation of CK2α Leads toUp-Regulation of the Cyclin-Dependent Kinase Inhibitor p27KIP1 in Conditions Unfavorable for the Growth of Myoblast Cells

2020 ◽  
Vol 54 (6) ◽  
pp. 1177-1198
Keyword(s):  
Cell Cycle ◽  
Transcription Factor ◽  
Cell Growth ◽  
Knockout Mouse ◽  
Cell Cycle Progression ◽  
Molecular Mechanisms ◽  
Kinase Inhibitor ◽  
Cyclin Dependent Kinase ◽  
Cycle Progression ◽  
Cyclin Dependent Kinase Inhibitor

BACKGROUND/AIMS: Compelling evidence indicates that CK2α, which is one of the two catalytic isoforms of protein kinase CK2, is required for cell viability and plays an important role in cell proliferation and differentiation. While much is known on CK2 in the context of disease states, particularly cancer, its critical role in non-cancerous cell growth has not been extensively investigated. METHODS: In the present study, we have employed a cell line derived from rat heart with inducible down-regulation of CK2α and CK2α-knockout mouse tissue to identify CK2-mediated molecular mechanisms regulating cell growth. For this, we have performed Incucyte® live-cell analysis and applied flow cytometry, western blot, immunoprecipitation, immunohistochemistry, RT-qPCR and luciferase-based methods. RESULTS: Here, we show that lack of CK2α results in significantly delayed cell cycle progression through G1, inhibition of cyclin E-CDK2 complex, decreased phosphorylation of Rb protein at S795, and inactivation of E2F transcription factor. These events are accompanied by nuclear accumulation and up-regulation of the cyclin-dependent kinase inhibitor p27KIP1 in cells and CK2α-knockout mouse tissues. We found that increased levels of p27KIP1 are mainly attributable to post-translational modifications, namely phosphorylation at S10 and T197 amino acid residues catalyzed by Dyrk1B and AMPK, respectively, as silencing of FoxO3A transcription factor, which activates CDKN1B the gene coding for p27KIP1, does not result in markedly decreased expression levels of the corresponding protein. Interestingly, simultaneous silencing of CK2α and p27KIP1 significantly impairs cell cycle progression without increasing cell death. CONCLUSION: Taken together, our study sheds light on the molecular mechanisms controlling cell cycle progression through G1 phase when myoblasts proliferation potential is impaired by CK2α depletion. Our results suggest that elevated levels of p27KIP1,which follows CK2α depletion, contribute to delay the G1-to-S phase transition. Effects seen when p27KIP1 is down-regulated are independent of CK2α and reflect the protective role exerted by p27KIP1 under unfavorable cell growth conditions.

Calcitonin Receptor-Mediated Growth Suppression of HEK-293 Cells Is Accompanied by Induction of p21WAF1/CIP1 and G2/M Arrest

1999 ◽  
Vol 13 (10) ◽  
pp. 1738-1750 ◽  
Author(s):  
Andreas Evdokiou ◽  
Liza-Jane Raggatt ◽  
Gerald J. Atkins ◽  
David M. Findlay
Keyword(s):  
Cell Cycle ◽  
Cell Growth ◽  
Antisense Oligonucleotide ◽  
Kinase Inhibitor ◽  
Cyclin Dependent Kinase ◽  
Hek 293 ◽  
Hek 293 Cells ◽  
Cyclin Dependent Kinase Inhibitor ◽  
293 Cells ◽  
Cdc2 Activity

Abstract We investigated the mechanisms by which calcitonin (CT) suppresses cellular proliferation, using HEK-293 cells stably transfected with either the rat C1a CT receptor (CTR) or the insert-negative form of the human CTR. CT treatment of clonal cell lines expressing either receptor type, but not untransfected HEK-293 cells, strongly suppressed cell growth in a concentration-dependent manner. The reduction in cell growth with CT treatment could not be attributed to cellular necrosis or apoptotic cell death, the latter assessed by both DNA fragmentation analysis and caspase 3 (CPP-32) assay. Growth inhibition was associated with an accumulation of cells in the G2 phase of the cell cycle. CT treatment of the human and rat CTR-expressing cell lines resulted in a rapid and sustained induction of mRNA encoding the cyclin-dependent kinase inhibitor, p21WAF1/CIP1, increased levels of which were maintained at least 48 h after initiation of treatment. Western blot analysis showed a rapid corresponding increase in p21WAF1/CIP1 protein, whereas protein levels of another member of the cyclin-dependent kinase inhibitor family, p27kip1, were unchanged. In parallel with the induction of p21, CT treatment reduced levels of p53 mRNA and protein. CT treatment resulted in a specific cell cycle block in G2, which was associated with inhibition of Cdc2/cyclin B kinase activity as measured by histone H1 phosphorylation. There was no evidence for p21 association with this complex despite the inhibition of Cdc2 activity. Evidence that p21 induction was causative of cell growth suppression was obtained from p21 antisense oligonucleotide experiments. Treatment with a p21 antisense oligonucleotide blocked induction of p21 expression and significantly reduced the CT-mediated growth inhibition. These observations suggest that p21 is required for the G2 arrest in response to CT, but argue against a direct role of p21 in the inhibition of Cdc2 activity. These studies suggest a novel regulation of cell cycle progression by CT and will provide a basis for detailed examination of the molecular mechanisms involved.

p21WAF1 Control of Epithelial Cell Cycle and Cell Fate

2002 ◽  
Vol 13 (6) ◽  
pp. 453-464 ◽  
Author(s):  
Wendy C. Weinberg ◽  
Mitchell F. Denning
Keyword(s):  
Cell Cycle ◽  
Epithelial Cell ◽  
Cell Fate ◽  
Cell Biology ◽  
Kinase Inhibitor ◽  
Growth Arrest ◽  
Nuclear Antigen ◽  
Central Position ◽  
Cyclin Dependent Kinase ◽  
Cyclin Dependent Kinase Inhibitor

As a broad-acting cyclin-dependent kinase inhibitor, p21WAF1 occupies a central position in the cell cycle regulation of self-renewing tissues such as oral mucosa and skin. In addition to regulating normal cell cycle progression decisions, p21WAF1 integrates genotoxic insults into growth arrest and apoptotic signaling pathways that ultimately determine cell fate. As a result of its complex interactions with cell cycle machinery and response to mutagenic agents, p21WAF1 also has stage-specific roles in epithelial carcinogenesis. Finally, a view is emerging of p21WAF1 as not merely a cyclin-dependent kinase inhibitor, but also as a direct participant in regulating genes involved in growth arrest, senescence, and aging, thus providing an additional layer of control over matters of the cell cycle. This review discusses these various roles played by p21WAF1 in cell cycle control, and attempts to relate these to epithelial cell biology, with special emphasis on keratinocytes. (Abbreviations used include the following: Brdu, 5-Bromo-2-deoxyuridine; cdk, cyclin-dependent kinase; EGF, epidermal growth factor; KIP, kinase inhibitor protein; PCNA, proliferating cell nuclear antigen; and TPA, 12-O-tetradecanoylphorbol-13-acetate.)

scholarly journals A comprehensive model for the proliferation–quiescence decision in response to endogenous DNA damage in human cells

2018 ◽  
Vol 115 (10) ◽  
pp. 2532-2537 ◽  
Author(s):  
Frank S. Heldt ◽  
Alexis R. Barr ◽  
Sam Cooper ◽  
Chris Bakal ◽  
Béla Novák
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Kinase Inhibitor ◽  
Human Cells ◽  
Cyclin Dependent Kinase ◽  
Restriction Point ◽  
Cyclin Dependent Kinase Inhibitor ◽  
Serum Stimulation ◽  
G1 Cells ◽  
External Stimuli

Human cells that suffer mild DNA damage can enter a reversible state of growth arrest known as quiescence. This decision to temporarily exit the cell cycle is essential to prevent the propagation of mutations, and most cancer cells harbor defects in the underlying control system. Here we present a mechanistic mathematical model to study the proliferation–quiescence decision in nontransformed human cells. We show that two bistable switches, the restriction point (RP) and the G1/S transition, mediate this decision by integrating DNA damage and mitogen signals. In particular, our data suggest that the cyclin-dependent kinase inhibitor p21 (Cip1/Waf1), which is expressed in response to DNA damage, promotes quiescence by blocking positive feedback loops that facilitate G1 progression downstream of serum stimulation. Intriguingly, cells exploit bistability in the RP to convert graded p21 and mitogen signals into an all-or-nothing cell-cycle response. The same mechanism creates a window of opportunity where G1 cells that have passed the RP can revert to quiescence if exposed to DNA damage. We present experimental evidence that cells gradually lose this ability to revert to quiescence as they progress through G1 and that the onset of rapid p21 degradation at the G1/S transition prevents this response altogether, insulating S phase from mild, endogenous DNA damage. Thus, two bistable switches conspire in the early cell cycle to provide both sensitivity and robustness to external stimuli.

345 GENE EXPRESSION IN OOCYTES AFTER MEIOTIC INHIBITION WITH THE CYCLIN-DEPENDENT KINASE INHIBITOR BUTYROLACTONE I

2010 ◽  
Vol 22 (1) ◽  
pp. 329
Author(s):  
C. L. V. Leal ◽  
S. Mamo ◽  
T. Fair ◽  
P. Lonergan
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Relative Abundance ◽  
Kinase Inhibitor ◽  
Expression Profiles ◽  
Cyclin Dependent Kinase ◽  
Oocyte Competence ◽  
Cyclin Dependent Kinase Inhibitor ◽  
Bovine Oocytes

Once removed from the follicle, mammalian oocytes resume meiosis spontaneously and progress through breakdown of the germinal vesicle to the matured state at metaphase II. The ability to reversibly inhibit such meiotic resumption has been reported and is a potentially useful method for studying developmental competence acquisition in oocytes as well as in some cases allowing flexibility in an IVF system where oocytes are collected from distant locations or on different days. The aim of the present study was to determine the effect of temporary inhibition of meiotic resumption using the cyclin-dependent kinase inhibitor butyrolactone I (BLI) on gene expression in bovine oocytes. Immature bovine oocytes were recovered from the ovaries of slaughtered heifers at a commercial abattoir and assigned to 1 of 4 groups: (1) Control: immature oocytes were collected either immediately or (2) after IVM for 24 h in TCM-199 containing 10 ng mL-1 EGF and 10% (v/v) FCS, (3) Inhibited oocytes collected either 24 h after incubation in the presence of 100 μM BLI in TCM-199 with 3 mg mL-1 BSA or (4) after meiotic inhibition for 24 h followed by in vitro maturation. All cultures were carried out at 38.5°C under 5% CO2 in air and maximum humidity. For mRNA relative abundance analysis, cumulus cells were removed and pools of 10 denuded oocytes were snap frozen in liquid nitrogen and stored at -80°C until use. A total of 42 transcripts, previously reported to be related to cell cycle regulation and/or oocyte competence were evaluated by quantitative real time PCR. Differences in relative abundance were analyzed by ANOVA and Student’s t-test. The majority of transcripts were downregulated (P < 0.05) after IVM in control oocytes (23 out of 42) and the same pattern was observed in inhibited oocytes that were allowed to mature. Twelve transcripts remained stable (P > 0.05) after IVM in control oocytes; of these, only two (PTTG1 and INHBA) did not show the same pattern in inhibited and matured oocytes. Few genes (7) were upregulated after IVM in control oocytes (P < 0.05) and of these, three (PLAT1, RBP1, and INHBB) were not upregulated in inhibited oocytes after IVM. Inhibited oocytes showed similar levels of expression (P > 0.05) as immature control oocytes, except for two genes (LUM and INHBB), which were increased in these oocytes (P < 0.05). The expression profiles of cell cycle genes were mostly unaffected by the BLI treatment. The few genes affected were previously reported as competence-related and could be useful markers of oocyte competence following pretreatment. In conclusion, the changes occurring in transcript abundance during oocyte maturation in vitro were to a large extent mirrored following inhibition of meiotic resumption prior to IVM and subsequent release from inhibition and maturation. CLV Leal was supported by CNPq, Brazil (PDE 201487/2007-1); Supported by Science Foundation Ireland (07/SRC/B1156).

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