N-Myc and the cyclin-dependent kinase inhibitors p18Ink4c and p27Kip1 coordinately regulate cerebellar development.
Ontology highlight
ABSTRACT:
SUBMITTER: Zindy F
PROVIDER: S-EPMC1518798 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Mutations in the MEN1 gene are associated with the multiple endocrine neoplasia syndrome type 1 (MEN1), which is characterized by parathyroid hyperplasia and tumors of the pituitary and pancreatic islets. The mechanism by which MEN1 acts as a tumor suppressor is unclear. We have recently shown that menin, the MEN1 protein product, interacts with mixed lineage leukemia (MLL) family proteins in a histone methyltransferase complex including Ash2, Rbbp5, and WDR5. Here, we show that menin directly regulates expression of the cyclin-dependent kinase inhibitors p27Kip1 and p18Ink4c. Menin activates transcription by means of a mechanism involving recruitment of MLL to the p27Kip1 and p18Ink4c promoters and coding regions. Loss of function of either MLL or menin results in down-regulation of p27Kip1 and p18Ink4c expression and deregulated cell growth. These findings suggest that regulation of cyclin-dependent kinase inhibitor transcription by cooperative interaction between menin and MLL plays a central role in menin's activity as a tumor suppressor.
| S-EPMC545577 | biostudies-literature
Project description:Cyclin D and cyclin-dependent kinase 4 (cdk4) are overexpressed in a variety of tumors, but their levels are not accurate indicators of oncogenic activity because an accessory factor such as p27(Kip1) is required to assemble this unstable dimer. Additionally, tyrosine (Y) phosphorylation of p27 (pY88) is required to activate cdk4, acting as an "on/off switch." We identified two SH3 recruitment domains within p27 that modulate pY88, thereby modulating cdk4 activity. Via an SH3-PXXP interaction screen, we identified Brk (breast tumor-related kinase) as a high-affinity p27 kinase. Modulation of Brk in breast cancer cells modulates pY88 and increases resistance to the cdk4 inhibitor PD 0332991. An alternatively spliced form of Brk (Alt Brk) which contains its SH3 domain blocks pY88 and acts as an endogenous cdk4 inhibitor, identifying a potentially targetable regulatory region within p27. Brk is overexpressed in 60% of breast carcinomas, suggesting that this facilitates cell cycle progression by modulating cdk4 through p27 Y phosphorylation. p27 has been considered a tumor suppressor, but our data strengthen the idea that it should also be considered an oncoprotein, responsible for cyclin D-cdk4 activity.
| S-EPMC4387217 | biostudies-literature
Project description:The transcriptional regulating protein of 132 kDa (TReP-132) has been identified in steroidogenic tissues, where it acts as a coactivator of steroidogenic factor 1 (SF-1). We show here that TReP-132 plays a role in the control of cell proliferation. In human HeLa cells, TReP-132 knockdown by using small interfering RNA resulted in increased G(1)-->S cell cycle progression. The growth-inhibitory effects of TReP-132 was further shown to be mediated by induction of G(1) cyclin-dependent kinase inhibitors p21(WAF1) (p21) and p27(KIP1) (p27) expression levels. As a consequence, G(1) cyclin/cyclin-dependent kinase activities and pRB phosphorylation were markedly reduced, and cell cycle progression was blocked in the G(1) phase. The stimulatory effect of TReP-132 on p21 and p27 gene transcription involved interaction of TReP-132 with the transcription factor Sp1 at proximal Sp1-binding sites in their promoters. Moreover, in different breast tumor cell lines, endogenous TReP-132 expression was positively related with a lower proliferation rate. In addition, TReP-132 knockdown resulted in enhanced cell proliferation and lowered p21 and p27 mRNA levels in the steroid-responsive and nonresponsive T-47D and MDA-MB-231 cell lines, respectively. Finally, a statistic profiling of human breast tumor samples highlighted that expression of TReP-132 is correlated with p21 and p27 levels and is associated with lower tumor incidence and aggressiveness. Together, these results identify TReP-132 as a basal cell cycle regulatory protein acting, at least in part, by interacting with Sp1 to activate the p21 and p27 gene promoters.
| S-EPMC1140623 | biostudies-literature
Project description:Induction of potent T-cell memory is the goal of vaccinations, but the molecular mechanisms that regulate the formation of memory CD8 T cells are not well understood. Despite the recognition that controls of cellular proliferation and apoptosis govern the number of memory T cells, the cell cycle regulatory mechanisms that control these key cellular processes in CD8 T cells during an immune response are poorly defined. Here, we have identified the cyclin-dependent kinase inhibitor p27(Kip1) as a critical regulator of the CD8 T-cell homeostasis at all phases of the T-cell response to an acute viral infection in mice. By acting as a timer for cell cycle exit, p27(Kip1) curtailed the programmed expansion of interleukin-2-producing memory precursors and markedly limited the magnitude and quality of CD8 T-cell memory. In the absence of p27(Kip1), CD8 T cells showed superior recall responses shortly after vaccination with recombinant Listeria monocytogenes. Additionally, we show that p27(Kip1) constrains proliferative renewal of memory CD8 T cells, especially of the effector memory subset. These findings provide critical insights into the cell cycle regulation of CD8 T-cell homeostasis and suggest that modulation of p27(Kip1) could bolster vaccine-induced T-cell memory and protective immunity.
| S-EPMC2953046 | biostudies-literature
Project description:Cyclin-dependent kinase 5 (Cdk5) is a serine/threonine kinase, and its kinase activity is dependent upon its association with either of the activating subunits p35 or p39, which are mainly expressed in neurons. We previously reported that Cdk5 knockout (KO) mice exhibit perinatal lethality, defective neuronal migration, and abnormal positioning of neurons in the facial motor nucleus and inferior olive in the hindbrain and Purkinje cells (PCs) in the cerebellum. In this study, we focused on the analysis of the role of Cdk5 in cerebellar development. For this purpose we generated midbrain-hindbrain-specific Cdk5 conditional knockout (MHB-Cdk5 KO) mice because the cerebellum develops postnatally, whereas Cdk5 KO mice die perinatally. Histological analysis of the MHB-Cdk5 KO mice revealed a significant size reduction of the cerebellum. In addition, profound disturbance of inward migration of granule cells (GC) was observed in the developing cerebellum. A normal dendritic development of the Purkinje cells (PCs) was disturbed in MHB-Cdk5 KO mice. Cultured Cdk5-null PCs showed similar dendritic abnormalities. These results indicate that Cdk5/p35 plays an important role in neuronal migration of PCs and GCs and dendrite formation of PCs in cerebellar development.
| S-EPMC3540197 | biostudies-literature
Project description:Rapamycin is a macrolide antibiotic that inhibits vascular smooth muscle cell proliferation and migration and that is used clinically on drug-eluting stents to inhibit in-stent restenosis. Although inhibition of cell migration is an asset in preventing restenosis, it also leads to impaired stent endothelialization, a significant limitation of current drug-eluting stent technology that necessitates prolonged antiplatelet therapy. We measured the ability of rapamycin to inhibit the migration of human umbilical vein endothelial cells (HUVECs) and human coronary artery endothelial cells (HCAEC) toward the chemoattractant vascular endothelial cell growth factor. Although acute administration of rapamycin had no effect, exposure for 24 h inhibited HUVEC and HCAEC migration. Disruption of the mTORC2 via small interfering RNA was also effective in inhibiting HCAEC migration. Treatment of HCAECs for this period with rapamycin produced an increase in the cyclin-dependent kinase inhibitor p27(Kip), through a decrease in the targeting of the protein for degradation by phosphorylation at Thr(187). ECs isolated from a knock-in mouse expressing p27(Kip1) with a mutation of this residue to an alanine, blocking this phosphorylation, exhibited reduced migration compared with wild-type controls. Silencing of p27(Kip1) with small interfering RNA blocked the effects of rapamycin on migration and tube formation as well as RhoA activation and cytoskeletal reorganization. We conclude that prolonged exposure of ECs to rapamycin increases p27(Kip1) and in turn inhibits RhoA activation, blocking cell migration and differentiation. These data elucidate the molecular mechanism underlying regulation of p27(Kip1) protein and cell migration by rapamycin.
| S-EPMC2852937 | biostudies-literature
Project description:MLL, involved in many chromosomal translocations associated with acute myeloid and lymphoid leukemia, has >50 known partner genes with which it is able to form in-frame fusions. Characterizing important downstream target genes of MLL and of MLL fusion proteins may provide rational therapeutic strategies for the treatment of MLL-associated leukemia. We explored downstream target genes of the most prevalent MLL fusion protein, MLL-AF4. To this end, we developed inducible MLL-AF4 fusion cell lines in different backgrounds. Overexpression of MLL-AF4 does not lead to increased proliferation in either cell line, but rather, cell growth was slowed compared with similar cell lines inducibly expressing truncated MLL. We found that in the MLL-AF4-induced cell lines, the expression of the cyclin-dependent kinase inhibitor gene CDKN1B was dramatically changed at both the RNA and protein (p27kip1) levels. In contrast, the expression levels of CDKN1A (p21) and CDKN2A (p16) were unchanged. To explore whether CDKN1B might be a direct target of MLL and of MLL-AF4, we used chromatin immunoprecipitation (ChIP) assays and luciferase reporter gene assays. MLL-AF4 binds to the CDKN1B promoter in vivo and regulates CDKN1B promoter activity. Further, we confirmed CDKN1B promoter binding by ChIP in MLL-AF4 as well as in MLL-AF9 leukemia cell lines. Our results suggest that CDKN1B is a downstream target of MLL and of MLL-AF4, and that, depending on the background cell type, MLL-AF4 inhibits or activates CDKN1B expression. This finding may have implications in terms of leukemia stem cell resistance to chemotherapy in MLL-AF4 leukemias.
| S-EPMC1236570 | biostudies-literature
Project description:Cyclin-dependent kinases (CDK) regulate cell cycle progression. During tumor development, altered expression and availability of CDKs strongly contribute to impaired cell proliferation, a hallmark of cancer. In recent years, targeted inhibition of CDKs has shown considerable therapeutic benefit in a variety of tumor entities. Their success is reflected in clinical approvals of specific CDK4/6 inhibitors for breast cancer. This review provides a detailed insight into the molecular mechanisms of CDKs as well as a general overview of CDK inhibition. It also summarizes the latest research approaches and current advances in the treatment of head and neck cancer with CDK inhibitors. Instead of monotherapies, combination therapies with CDK inhibitors may especially provide promising results in tumor therapy. Indeed, recent studies have shown a synergistic effect of CDK inhibition together with chemo- and radio- and immunotherapy in cancer treatment to overcome tumor evasion, which may lead to a renaissance of CDK inhibitors.
| S-EPMC8773807 | biostudies-literature
Project description:Cyclin-dependent kinases (CDKs) have been considered promising drug targets for a number of years, but most CDK inhibitors have failed rigorous clinical testing. Recent studies demonstrating clear anticancer efficacy and reduced toxicity of CDK4/6 inhibitors such as palbociclib and multi-CDK inhibitors such as dinaciclib have rejuvenated the field. Favorable results with palbociclib and its recent U.S. Food and Drug Administration approval demonstrate that CDK inhibitors with narrow selectivity profiles can have clinical utility for therapy based on individual tumor genetics. A brief overview of results obtained with ATP-competitive inhibitors such as palbociclib and dinaciclib is presented, followed by a compilation of new avenues that have been pursued toward the development of novel, non-ATP-competitive CDK inhibitors. These creative ways to develop CDK inhibitors are presented along with crystal structures of these agents complexed with CDK2 to highlight differences in their binding sites and mechanisms of action. The recent successes of CDK inhibitors in the clinic, combined with the potential for structure-based routes to the development of non-ATP-competitive CDK inhibitors, and evidence that CDK inhibitors may have use in suppressing chromosomal instability and in synthetic lethal drug combinations inspire optimism that CDK inhibitors will become important weapons in the fight against cancer.
| S-EPMC4613943 | biostudies-literature
Project description:Cyclin-dependent kinase 5 (Cdk5) plays a key role in the development of the mammalian nervous system; it phosphorylates a number of targeted proteins involved in neuronal migration during development to synaptic activity in the mature nervous system. Its role in the initial stages of neuronal commitment and differentiation of neural stem cells (NSCs), however, is poorly understood. In this study, we show that Cdk5 phosphorylation of p27(Kip1) at Thr187 is crucial to neural differentiation because 1) neurogenesis is specifically suppressed by transfection of p27(Kip1) siRNA into Cdk5(+/+) NSCs; 2) reduced neuronal differentiation in Cdk5(-/-) compared with Cdk5(+/+) NSCs; 3) Cdk5(+/+) NSCs, whose differentiation is inhibited by a nonphosphorylatable mutant, p27/Thr187A, are rescued by cotransfection of a phosphorylation-mimicking mutant, p27/Thr187D; and 4) transfection of mutant p27(Kip1) (p27/187A) into Cdk5(+/+) NSCs inhibits differentiation. These data suggest that Cdk5 regulates the neural differentiation of NSCs by phosphorylation of p27(Kip1) at theThr187 site. Additional experiments exploring the role of Ser10 phosphorylation by Cdk5 suggest that together with Thr187 phosphorylation, Ser10 phosphorylation by Cdk5 promotes neurite outgrowth as neurons differentiate. Cdk5 phosphorylation of p27(Kip1), a modular molecule, may regulate the progress of neuronal differentiation from cell cycle arrest through differentiation, neurite outgrowth, and migration.
| S-EPMC2954124 | biostudies-literature