Down-regulation Of P27 Kip1 Expression Research Articles

Nanog induces suppression of senescence through downregulation of p27KIP1 expression

A comprehensive analysis of the molecular network of cellular factors establishing and maintaining pluripotency as well as self renewal of pluripotent stem cells is key for further progress in understanding basic stem cell biology. Nanog is necessary for the natural induction of pluripotency in early mammalian development but dispensable for both its maintenance and its artificial induction. To gain further insight into the molecular activity of Nanog, we analyzed the outcomes of Nanog gain-of-function in various cell models employing a recently developed biologically active recombinant cell-permeant protein, Nanog-TAT. We found that Nanog enhances the proliferation of both NIH 3T3 and primary fibroblast cells. Nanog transduction into primary fibroblasts results in suppression of senescence-associated β-galactosidase activity. Investigation of cell cycle factors revealed that transient activation of Nanog correlates with consistent downregulation of the cell cycle inhibitor p27KIP1 (also known as CDKN1B). By performing chromatin immunoprecipitation analysis, we confirmed bona fide Nanog-binding sites upstream of the p27KIP1 gene, establishing a direct link between physical occupancy and functional regulation. Our data demonstrates that Nanog enhances proliferation of fibroblasts through transcriptional regulation of cell cycle inhibitor p27 gene.

Nanog induces suppression of senescence through downregulation of p27KIP1 expression.

ABSTRACTA comprehensive analysis of the molecular network of cellular factors establishing and maintaining pluripotency as well as self renewal of pluripotent stem cells is key for further progress in understanding basic stem cell biology. Nanog is necessary for the natural induction of pluripotency in early mammalian development but dispensable for both its maintenance and its artificial induction. To gain further insight into the molecular activity of Nanog, we analyzed the outcomes of Nanog gain-of-function in various cell models employing a recently developed biologically active recombinant cell-permeant protein, Nanog-TAT. We found that Nanog enhances the proliferation of both NIH 3T3 and primary fibroblast cells. Nanog transduction into primary fibroblasts results in suppression of senescence-associated β-galactosidase activity. Investigation of cell cycle factors revealed that transient activation of Nanog correlates with consistent downregulation of the cell cycle inhibitor p27KIP1 (also known as CDKN1B). By performing chromatin immunoprecipitation analysis, we confirmed bona fide Nanog-binding sites upstream of the p27KIP1 gene, establishing a direct link between physical occupancy and functional regulation. Our data demonstrates that Nanog enhances proliferation of fibroblasts through transcriptional regulation of cell cycle inhibitor p27 gene.

Activation of Notch3 promotes pulmonary arterial smooth muscle cells proliferation via Hes1/p27Kip1 signaling pathway

Activation of the Notch3 cascade is involved in the development of pulmonary arterial hypertension by stimulating the proliferation of vascular smooth muscle cells. However, the detailed molecular mechanisms underlying this effect are still unclear. The present study aims to address this issue. We demonstrated that over-expression of intracellular domain of the Notch3 receptor (NICD3) by adenovirus transfection dramatically induced proliferation of primary cultured pulmonary artery smooth muscle cells. This was accompanied with up-regulation of Hes1 protein and down-regulation of p27Kip1 protein. More importantly, we observed that prior silencing of Hes1 with siRNA blocked NICD3 over-expression-induced p27Kip1 reduction and cell proliferation. The present study suggests that Hes1 lies downstream of NICD3 and particularly mediates Notch3 signaling-induced proliferation of pulmonary arterial smooth muscle cells by down-regulation of p27Kip1 expression.

IL-7 splicing variant IL-7δ5 induces human breast cancer cell proliferation via activation of PI3K/Akt pathway

Various tumor cells express interleukin 7 (IL-7) and IL-7 variants. IL-7 has been confirmed to stimulate solid tumor cell proliferation. However, the effect of IL-7 variants on tumor cell proliferation remains unclear. In this study, we evaluated the role of IL-7δ5 (an IL-7 variant lacking exon 5) on proliferation and cell cycle progression of human MDA-MB-231 and MCF-7 breast cancer cells. The results showed that IL-7δ5 promoted cell proliferation and cell cycle progression from G1 phase to G2/M phase, associated with upregulation of cyclin D1 expression and the downregulation of p27kip1 expression. Mechanistically, we found that IL-7δ5 induced the activation of Akt. Inhibition of PI3K/Akt pathway by LY294002 reversed the proliferation and cell cycle progression of MDA-MB-231 and MCF-7 cells induced by IL-7δ5. In conclusion, our findings demonstrate that IL-7δ5 variant induces human breast cancer cell proliferation and cell cycle progression via activation of PI3K/Akt pathway. Thus, IL-7δ5 may be a potential target for human breast cancer therapeutics intervention.

Increase in Ara-C cytotoxicity in the presence of valproate, a histone deacetylase inhibitor, is associated with the concurrent expression of cyclin D1 and p27 Kip1 in acute myeloblastic leukemia cells

The effects of valproate and butyrate were investigated in an acute myeloblastic cell line (OCI/AML-2) on cytotoxicity, cell cycle profile and expression of cell cycle regulating proteins in the presence of cytarabine (Ara-C) and etoposide. As a single agent valproate and butyrate inhibited AML cell growth but did not significantly induce cell death. A dramatic increase in cytotoxicity was observed when combining valproate or butyrate with Ara-C, whereas, co-addition of them with etoposide had much smaller effect on cell death. Valproate induced a clear G1 phase arrest and up-regulated cyclin D1 expression in the presence of Ara-C and etoposide. In addition, valporate was able to block the Ara-C-induced down-regulation of p27 Kip1 expression but not that induced by etoposide.

Deregulated Expression of the Homeobox Gene Cux-1 in Transgenic Mice Results in Downregulation of p27kip1 Expression during Nephrogenesis, Glomerular Abnormalities, and Multiorgan Hyperplasia

Cux-1 is a murine homeobox gene that is highly expressed in the developing kidney with expression restricted to the nephrogenic zone. Cux-1 is highly expressed in cyst epithelium of polycystic kidneys from C57BL/6J-cpk/cpk mice, but not in kidneys isolated from age-matched phenotypically normal littermates. To further elucidate the role of Cux-1 in renal development, we generated transgenic mice expressing Cux-1 under the control of the CMV immediate early gene promoter. Mice constitutively expressing Cux-1 developed multiorgan hyperplasia and organomegaly, but not an overall increase in body size. Transgenic kidneys were enlarged 50% by 6 weeks of age, with the increased growth primarily restricted to the cortex. Proliferating cells were found in proximal and distal tubule epithelium throughout the cortex, and the squamous epithelium that normally lines Bowman's capsule was replaced with proximal tubule epithelium. However, the total number of nephrons was not increased. In the developing kidneys of transgenic mice, Cux-1 was ectopically expressed in more highly differentiated tubules and glomeruli, and this was associated with reduced expression of the cyclin kinase inhibitor, p27. Transient transfection experiments revealed that Cux-1 is an inhibitor of p27 promoter activity. These results suggest that Cux-1 regulates cell proliferation during early nephrogenesis by inhibiting expression of p27.

Down-regulation of p27Kip1 expression is required for development and function of T cells.

The proliferation of T cells is regulated in a development-dependent manner, but it has been unclear whether proliferation is essential for T cell differentiation. The cyclin-dependent kinase inhibitor p27(Kip1) is abundant throughout development in cells of the T cell lineage, with the exception of late stage CD4(-)CD8(-) thymocytes and activated mature T cells, both of which show a high rate of proliferation. The role of down-regulation of p27(Kip1) expression in T cell development and function has now been investigated by the generation and characterization of three strains of p27 transgenic mice that express the transgene at various levels specifically in the T cell lineage. The numbers of thymocytes at CD4(+)CD8(+), CD4(+)CD8(-), and CD4(-)CD8(+) stages of development as well as those of mature T cells in peripheral lymphoid tissues were reduced in transgenic mice in a manner dependent on the level of p27(Kip1) expression. The development of thymocytes in the transgenic strain in which p27(Kip1) is most abundant (p27-Tg(high) mice) appeared to be blocked at the CD4(-)CD8(-)CD25(+)CD44(low) stage. Peripheral T cells from p27-Tg(high) mice exhibited a reduced ability to proliferate in response to mitogenic stimulation compared with wild-type T cells. Moreover, Ag-induced formation of germinal centers and Ig production were defective in p27-Tg(high) mice. These results suggest that down-regulation of p27(Kip1) expression is required for the development, proliferation, and immunoresponsiveness of T cells.

CD28 induces cell cycle progression by IL-2-independent down-regulation of p27kip1 expression in human peripheral T lymphocytes

CD28 induces cell cycle progression by IL-2-independent down-regulation of p27kip1 expression in human peripheral T lymphocytes

BPV-4 E8 transforms NIH3T3 cells, up-regulates cyclin A and cyclin A-associated kinase activity and de-regulates expression of the cdk inhibitor p27Kip1.

The E8 open reading frame of Bovine papillomavirus type 4 (BPV-4) encodes a small (42 amino acid) hydrophobic polypeptide localized to cellular membranes and capable of conferring an anchorage-independent (AI) growth phenotype on primary bovine cells co-transfected with BPV-4 E7 ORF and an activated ras gene. To further study the function of E8 independently of other viral gene products, we have expressed it in the murine fibroblast cell line, NIH3T3. Cells expressing E8 are capable of AI growth and escape growth arrest after serum withdrawal. E8 deregulates cyclin A expression, induces transactivation of the human cyclin A gene promoter and increases endogenous protein levels in cells maintained in short-term suspension culture and in low-serum (LS). Both these culture conditions promote downregulation of cyclin A in control cells. In LS growth conditions E8 permits sustained cyclin A-associated kinase activity but not cyclin E-cdk2 activity. Cyclin A-cdk2 activity and, in part, cyclin A gene expression are regulated by the cdk inhibitor p27Kip1. Expression of this cdk inhibitor is also de-regulated in E8 cells, with high levels being detected under all culture conditions tested. These data suggest that the ability of BPV-4 E8 to transform NIH3T3 cells is associated with upregulation of cyclin A-associated kinase activity and de-regulated expression of the cdk inhibitor p27Kip1 and does not rely on down-regulation of p27Kip1 expression. Analysis of E8 mutants indicate that the hydrophilic 'tail' of the molecule (residues 31-42) is required for cell transformation, as assessed by anchorage-independent growth, while a form of E8 with expression restricted to the Endoplasmic Reticulum/cis-Golgi membranes by addition of a 'KDEL' retention signal revealed that the sub-cellular localization is an important determinant of E8 biological activity.