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Tourigny MR, Ursini-Siegel J, Lee H, Toellner KM, Cunningham AF, Franklin DS, Ely S, Chen M, Qin XF, Xiong Y, MacLennan ICM, Chen-Kiang S. CDK inhibitor p18(INK4c) is required for the generation of functional plasma cells. Immunity 2002; 17:179-89. [PMID: 12196289 DOI: 10.1016/s1074-7613(02)00364-3] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
B cell terminal differentiation is associated with the onset of high-level antibody secretion and cell cycle arrest. Here the cyclin-dependent kinase (CDK) inhibitor p18(INK4c) is shown to be required within B cells for both terminating cell proliferation and differentiation of functional plasma cells. In its absence, B cells hyperproliferate in germinal centers and extrafollicular foci in response to T-dependent antigens but serum antibody titers are severely reduced, despite unimpaired germinal center formation, class switch recombination, variable region-directed hypermutation, and differentiation to antibody-containing plasmacytoid cells. The novel link between cell cycle control and plasma cell differentiation may, at least in part, relate to p18(INK4c) inhibition of CDK6. Cell cycle arrest mediated by p18(INK4C) is therefore requisite for the generation of functional plasma cells.
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Affiliation(s)
- Michelle R Tourigny
- Department of Pathology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA
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52
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Lazaro JB, Bailey PJ, Lassar AB. Cyclin D-cdk4 activity modulates the subnuclear localization and interaction of MEF2 with SRC-family coactivators during skeletal muscle differentiation. Genes Dev 2002; 16:1792-805. [PMID: 12130539 PMCID: PMC186397 DOI: 10.1101/gad.u-9988r] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Prior work has indicated that D-type cyclin-cdk4 complexes, which are only active in proliferating cells, can suppress the skeletal muscle differentiation program in proliferating myoblasts. In this study, we show that cyclin D-cdk activity can block the activity of the MEF2 family of transcriptional regulators, which are crucial regulators of skeletal muscle gene expression. We have found that cyclin D-cdk activity blocks the association of MEF2C with the coactivator protein GRIP-1 and thereby inhibits the activity of MEF2. During skeletal muscle differentiation, GRIP-1 is localized to punctate nuclear structures and can apparently tether MEF2 to such structures. Cotransfection of GRIP-1 can both potentiate the transcriptional activity of a Gal4-MEF2C construct and induce MEF2C localization to punctate nuclear structures. Consistent with the absence of punctate nuclear GRIP-1 in proliferating myoblasts, we have found that ectopic cyclin D-cdk4 expression disrupts the localization of both GRIP-1 and MEF2C to these punctate subnuclear structures. Our findings indicate that cyclin D-cdk4 activity represses skeletal muscle differentiation in proliferating cells by blocking the association of MEF2 with the coactivator GRIP-1 and concomitantly disrupts the association of these factors with punctate nuclear subdomains within the cell.
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Affiliation(s)
- Jean-Bernard Lazaro
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
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53
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Abstract
The cell cycle behavior of hematopoietic cells varies from extended quiescence to spectacular proliferation. Cell cycle regulators choreograph these transitions through variation in the makeup of cyclin-dependent kinase (cdk)-containing complexes and through alteration in protein expression levels and subcellular localization. The mechanisms through which cell cycle regulators couple proliferation, differentiation and survival is coming into sharper focus. Cdk-inhibitors, once thought of solely in terms of a checkpoint function on cycling, are now known to interact directly with proteins and pathways central to differentiation and apoptosis. By shuttling between binding partners committed to discrete functional pathways, cell cycle regulators may directly coordinate proliferation with differentiation, migration and apoptosis.
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Affiliation(s)
- Richard A Steinman
- Department of Medicine and Pharmacology, E1052 BST, 200 Lothrop Street, Pittsburgh, Pennsylvania, PA 15213, USA.
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54
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Leshem Y, Halevy O. Phosphorylation of pRb is required for HGF-induced muscle cell proliferation and is p27kip1-dependent. J Cell Physiol 2002; 191:173-82. [PMID: 12064460 DOI: 10.1002/jcp.10089] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Hepatocyte growth factor (HGF) plays a crucial role in the differentiation of skeletal muscle cells, where a process in which the retinoblastoma protein (pRb) has been implicated. We addressed the role of pRb in HGF-mediated effects on the proliferation and differentiation of adult skeletal muscle myoblasts. HGF shifted pRb to its hyperphosphorylation forms and increased the transactivation of E2F1, a transcription factor required for S phase entry. A constitutively active pRb mutant blocked HGF-dependent pRb phosphorylation and transactivation of E2F1 and increased cell proliferation. Accordingly, this mutant reversed the inhibitory effects of HGF on the expression of the cyclin-dependent kinase (CDK) inhibitor p27 and myogenic differentiation markers. HGF-mediated pRb phosphorylation was reversed by ectopic expression of p27, but neither the myogenic regulatory factor, MEF2, nor the myogenic inhibitory protein Twist had that effect. These results suggest that in response to HGF signaling, there is a decrease in p27 expression that results in an accumulation of hyperphosphorylated Rb protein, and subsequent progression of myoblasts into the G1 phase of the cell cycle.
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MESH Headings
- Animals
- Animals, Newborn
- Avian Proteins
- Cell Cycle Proteins/metabolism
- Cell Differentiation/drug effects
- Cell Differentiation/physiology
- Cell Division/drug effects
- Cell Division/physiology
- Cells, Cultured
- Chickens
- Cyclin-Dependent Kinase Inhibitor p27
- DNA-Binding Proteins
- E2F Transcription Factors
- E2F1 Transcription Factor
- G1 Phase/drug effects
- G1 Phase/physiology
- Hepatocyte Growth Factor/genetics
- Hepatocyte Growth Factor/metabolism
- Hepatocyte Growth Factor/pharmacology
- MEF2 Transcription Factors
- Muscle Fibers, Skeletal/cytology
- Muscle Fibers, Skeletal/drug effects
- Muscle Fibers, Skeletal/metabolism
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/growth & development
- Muscle, Skeletal/metabolism
- Mutation/drug effects
- Mutation/physiology
- Myogenic Regulatory Factors/drug effects
- Myogenic Regulatory Factors/genetics
- Myogenic Regulatory Factors/metabolism
- Phosphorylation/drug effects
- Promoter Regions, Genetic/drug effects
- Promoter Regions, Genetic/genetics
- Retinoblastoma Protein/drug effects
- Retinoblastoma Protein/genetics
- Retinoblastoma Protein/metabolism
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Tumor Suppressor Proteins/metabolism
- Twist-Related Protein 1
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Affiliation(s)
- Yael Leshem
- Department of Animal Sciences, The Hebrew University of Jerusalem, Rehovot, Israel
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55
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Cossins J, Vernon AE, Zhang Y, Philpott A, Jones PH. Hes6 regulates myogenic differentiation. Development 2002; 129:2195-207. [PMID: 11959828 DOI: 10.1242/dev.129.9.2195] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Hes6 is a basic helix-loop-helix transcription factor homologous to Drosophila Enhancer of Split (EoS) proteins. It is known to promote neural differentiation and to bind to Hes1, a related protein that is part of the Notch signalling pathway, affecting Hes1-regulated transcription. We show that Hes6 is expressed in the murine embryonic myotome and is induced on C2C12 myoblast differentiation in vitro. Hes6 binds DNA containing the Enhancer of Split E box (ESE) motif, the preferred binding site of Drosophila EoS proteins, and represses transcription of an ESE box reporter. When overexpressed in C2C12 cells, Hes6 impairs normal differentiation, causing a decrease in the induction of the cyclin-dependent kinase inhibitor, p21Cip1, and an increase in the number of cells that can be recruited back into the cell cycle after differentiation in culture. In Xenopus embryos, Hes6 is co-expressed with MyoD in early myogenic development. Microinjection of Hes6 RNA in vivo in Xenopus embryos results in an expansion of the myotome, but suppression of terminal muscle differentiation and disruption of somite formation at the tailbud stage. Analysis of Hes6 mutants indicates that the DNA-binding activity of Hes6 is not essential for its myogenic phenotype, but that protein-protein interactions are. Thus, we demonstrate a novel role for Hes6 in multiple stages of muscle formation.
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Affiliation(s)
- Judy Cossins
- Cancer Research UK, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford, UK
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56
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Zhu Y, Lee HC, Zhang L. An examination of heme action in gene expression: heme and heme deficiency affect the expression of diverse genes in erythroid k562 and neuronal PC12 cells. DNA Cell Biol 2002; 21:333-46. [PMID: 12042072 DOI: 10.1089/104454902753759744] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The aim of this study was to identify key genes whose expression is altered by heme and heme deficiency in the human erythroleukemia K562 cells and in the NGF-induced rat pheochromocytoma neuronal PC12 cells, respectively. By quantitative RT-PCR, Northern blotting, and Western blotting analyses, we found that the expression of the CDK inhibitors p18 and p21 was upregulated at the early and late stages of heme-induced erythroid differentiation of K562 cells, respectively, while the expression of cyclin D1 was downregulated. Data from succinyl acetone and desferrioxamine treatments suggest that these effects of heme in K562 cells were specific. Further, by microarray expression analysis, we found that inhibition of heme synthesis by succinyl acetone in NGF-induced PC12 cells drastically altered the expression of several groups of important neuronal genes, including the structural genes encoding neurofilament proteins and synaptic vesicle proteins, regulatory genes encoding signaling components beta-arrestin and p38 MAPK, and stress-response genes encoding hsp70. These results show that heme and heme deficiency affect the expression of diverse genes in a cell-type specific manner in mammalian cells, and that heme, although needed at different levels, is critical for both erythropoiesis and neurogenesis. These studies provide insights into how heme may act to control diverse regulatory processes in mammals.
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Affiliation(s)
- Yonghua Zhu
- Department of Biochemistry, NYU School of Medicine, New York, NY 10016, USA
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57
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Kulkarni MS, Daggett JL, Bender TP, Kuehl WM, Bergsagel PL, Williams ME. Frequent inactivation of the cyclin-dependent kinase inhibitor p18 by homozygous deletion in multiple myeloma cell lines: ectopic p18 expression inhibits growth and induces apoptosis. Leukemia 2002; 16:127-34. [PMID: 11840272 DOI: 10.1038/sj.leu.2402328] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2001] [Accepted: 07/27/2001] [Indexed: 11/08/2022]
Abstract
Multiple myeloma (MM) is a clonal neoplasm of plasma cells which offers an excellent model to study multistep molecular oncogenesis. In 20-25% of primary tumors and cell lines examined, cyclin D1 is overexpressed due to the translocation t(11;14)(q13;q32). We have characterized cyclin-dependent kinase inhibitor p15 (CDKN2B), p16 (CDKN2A) and p18 (CDKN2C) deletions in cyclin D1-expressing and non-expressing MM cell lines. p18 was found to be frequently deleted (38%); in some cases p18 deletions coexisted with hemizygous p16 deletion. To examine the function of p18 as a putative tumor suppressor in myeloma cells, a zinc-inducible p18 construct was stably transfected into KMS12, a MM cell line with biallelic p18 and monoallelic p16 deletions as well as cyclin D1 overexpression. Ectopic expression of p18 caused 40-45% growth suppression as determined by trypan blue exclusion and MTS assays. p18 induction also resulted in apoptosis, suggesting that inhibition of the cyclin D1/CDK/pRb pathway in these tumor cells could be a crucial step toward the induction of tumor regression via apoptotic cell death. This cell cycle pathway is thus frequently mutated and provides a potentially novel target for gene therapeutic or pharmacologic approaches to human myeloma.
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Affiliation(s)
- M S Kulkarni
- Department of Internal Medicine, University of Virginia School of Medicine, Charlottesville, VA, USA
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58
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Chapter 3 Interactions between the cell cycle and the myogenic program. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s1569-1799(02)11003-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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59
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Huppertz B, Tews DS, Kaufmann P. Apoptosis and syncytial fusion in human placental trophoblast and skeletal muscle. INTERNATIONAL REVIEW OF CYTOLOGY 2001; 205:215-53. [PMID: 11336392 DOI: 10.1016/s0074-7696(01)05005-7] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Skeletal muscle fibers and placental villous trophoblast are the main representatives of syncytia in the human. Both syncytia are derived from fusion of mononucleated stem cells, show a high degree of differentiation, and have lost their generative potency. Consequently, for their growth both depend on fusion of additional stem cells. There is evidence that syncytial fusion is directly or indirectly related to apoptotic events: As early as in the differentiated stages of the mononucleated stem cells, initiation stages of the apoptosis cascade have been observed. After syncytial fusion progression of the cascade is retarded or blocked by a variety of mechanisms. In this review we emphasize the links between apoptosis cascade, differentiation pathways and syncytial fusion. It needs to be elucidated whether these processes simply take place in parallel, both temporally and spatially, or whether there are causal connections between apoptosis cascade and syncytial fusion. Based on recent data obtained for placental villous trophoblast, it is tempting to speculate that early molecular mechanisms of the apoptosis cascade are involved in differentiation and syncytial fusion. Data obtained in skeletal muscles support this assumption and reveal a considerable degree of homology in genesis, maintenance and turnover of both tissues.
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Affiliation(s)
- B Huppertz
- Department of Anatomy, University Hospital, Aachen, Germany
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60
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Steinman RA, Lu Y, Yaroslavskiy B, Stehle C. Cell cycle-independent upregulation of p27Kip1 by p21Waf1 in K562 cells. Oncogene 2001; 20:6524-30. [PMID: 11641776 DOI: 10.1038/sj.onc.1204800] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2001] [Revised: 06/26/2001] [Accepted: 07/05/2001] [Indexed: 11/08/2022]
Abstract
Cellular differentiation frequently involves sequential peaks in the expression of cyclin-dependent kinase inhibitors (cdki's). For example, an increase in levels of the cdki p27Kip1 follows upregulation of p21Waf1 in several cell types induced to differentiate by diverse stimuli. In this study, we have investigated whether p21Waf1 expression itself, rather than the differentiating agent, could be increasing p27Kip1 protein levels. We used an inducible p21Waf1 expression vector in a K562 leukemic cell model which we had previously shown to initiate differentiation following p21Waf1 upregulation. The current study reports that p21Waf1 upregulated p27Kip1 protein without altering p27Kip1 mRNA levels. This effect did not depend on G1-phase arrest-the increase in p27Kip1 occurred at all phases of the cell cycle. p21Waf1-expressing extracts inhibited phosphorylation of p27Kip1 on threonine-187, leading to decreased ubiquitination and decreased proteasomal destruction of p27Kip1. In K562 cells, upregulation of p27Kip1 by p21Waf1 during differentiation facilitated an ordered transition between these two cdki's, each of which may distinctly influence the differentiation process.
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Affiliation(s)
- R A Steinman
- Department of Medicine, University of Pittsburgh School of Medicine, 200 Lothrop Street, Pittsburgh, PA 15213, USA.
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61
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Kovalev GI, Franklin DS, Coffield VM, Xiong Y, Su L. An important role of CDK inhibitor p18(INK4c) in modulating antigen receptor-mediated T cell proliferation. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2001; 167:3285-92. [PMID: 11544316 PMCID: PMC4435948 DOI: 10.4049/jimmunol.167.6.3285] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The inhibitors of cyclin-dependent kinase (CDK) 4 (INK4) bind CDK4/6 to prevent their association with D-cyclins and G(1) cell cycle initiation and progression. We report here that among the seven CDK inhibitors, p18(INK4c) played an important role in modulating TCR-mediated T cell proliferation. Loss of p18(INK4c) in T cells led to hyperproliferation in response to CD3 stimulation. p18(INK4c)-null mice developed lymphoproliferative disorder and T cell lymphomas. Expression of IL-2, IL-2R-alpha, and the major G(1) cell cycle regulatory proteins was not altered in p18-null T cells. Both FK506 and rapamycin efficiently inhibited proliferation of p18-null T cells. In activated T cells, p18(INK4c) remained constant, and preferentially associated with and inhibited CDK6 but not CDK4. We propose that p18(INK4c) sets an inhibitory threshold in T cells and one function of CD28 costimulation is to counteract the p18(INK4c) inhibitory activity on CDK6-cyclin D complexes. The p18(INK4c) protein may provide a novel target to modulate T cell immunity.
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Affiliation(s)
- Grigoriy I. Kovalev
- Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina, Chapel Hill, NC 27599
- Department of Microbiology and Immunology, School of Medicine, University of North Carolina, Chapel Hill, NC 27599
| | - David S. Franklin
- Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina, Chapel Hill, NC 27599
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, NC 27599
| | - V. McNeil Coffield
- Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina, Chapel Hill, NC 27599
- Department of Microbiology and Immunology, School of Medicine, University of North Carolina, Chapel Hill, NC 27599
| | - Yue Xiong
- Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina, Chapel Hill, NC 27599
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, NC 27599
| | - Lishan Su
- Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina, Chapel Hill, NC 27599
- Department of Microbiology and Immunology, School of Medicine, University of North Carolina, Chapel Hill, NC 27599
- Address correspondence and reprint requests to Dr. Lishan Su, Lineberger Comprehensive Cancer Center, Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27599.
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62
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Negishi Y, Ui N, Nakajima M, Kawashima K, Maruyama K, Takizawa T, Endo H. p21Cip-1/SDI-1/WAF-1 gene is involved in chondrogenic differentiation of ATDC5 cells in vitro. J Biol Chem 2001; 276:33249-56. [PMID: 11406616 DOI: 10.1074/jbc.m010127200] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Development of skeletal cartilage is characterized with coupling growth arrest and cell differentiation. Here, to understand the cyclin-dependent kinase inhibitors involved in the progression of chondrogenic differentiation, we examined changes in the expression levels of cyclin-dependent kinase inhibitor members using mouse ATDC5 prechondrocytes as a widely used in vitro model of cartilage differentiation. Up-regulation of p21 and p27 mRNA was observed following a decrease in growth rate of prechondrocytes, and both transcripts subsequently accumulated during chondrogenic differentiation; p15, p18, and p19 mRNA, in contrast, did not change during differentiation. Only the up-regulation of p21 mRNA during differentiation was prevented by the continuous treatment of early chondrogenic inhibitor, parathyroid hormone, indicating a close correlation between differentiation and p21 induction in ATDC5 cells. Therefore, to examine the role of p21 during chondrogenesis, we established stable cell lines overexpressing full-length p21 antisense RNA in ATDC5. The reduction of endogenous p21 in these cell lines caused inhibition of early chondrogenic differentiation in ATDC5, indicating that p21 gene plays an important role in this process of the cells in vitro. Furthermore, the level of p21 protein and p21.CDK2 complexes transiently increased during differentiation, but not in undifferentiated cells, leading to a decrease in CDK2-associated kinase. However, differentiation-dependent expressed p21 protein was degraded by a proteasome-dependent pathway. Thus, the progression of chondrogenic differentiation requires down-regulation of CDK2-associated kinase with an increase in p21 protein and subsequent degradation of this protein by a proteasomal pathway.
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Affiliation(s)
- Y Negishi
- Department of Physiological Chemistry, Faculty of Pharmaceutical Sciences, Teikyo University, Sagamiko, Kanagawa 199-0195, Japan.
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63
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Wainwright LJ, Lasorella A, Iavarone A. Distinct mechanisms of cell cycle arrest control the decision between differentiation and senescence in human neuroblastoma cells. Proc Natl Acad Sci U S A 2001; 98:9396-400. [PMID: 11481496 PMCID: PMC55432 DOI: 10.1073/pnas.161288698] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Retinoic acid (RA) induces cell cycle arrest and differentiation of human neuroblastoma (NB) cells. Typically, NB cells differentiate along the neuronal lineage, but quiescent, "flat" cell types frequently have been described after treatment with differentiating agents. Two indistinguishable subclones of the cell line SK-N-SH, SK-N-SH-N (SH-N) and SK-N-SH-F (SH-F), display dramatically different responses to RA. In SH-N, RA induces neuronal differentiation, but in SH-F it transforms the small neuroblastic cells into large, flattened, epithelium-like cells. Here we analyze the mechanistic basis for the different effects of RA in the two NB subclones. First, we show that the flattened RA-treated SH-F expresses markers of cells undergoing replicative senescence. Inhibition of DNA synthesis by RA is significantly more rapid in SH-F than in SH-N. SH-F, which expresses basal amounts of p16(INK4A), responds to RA with elevation of p18(INK4C), marked down-regulation of cyclin D1, and swift inhibition of cyclin D-dependent kinases (cdks). Conversely, after addition of RA, SH-N retains cell cycling due to high expression of cyclin D1, the absence of Ink4 inhibitors, and accumulation of p21(Cip1). These changes result in sustained cdk activity. Accordingly, overexpression of p21(Cip1) but not p16(INK4A) induces neuronal differentiation of untreated NB cells. We propose that rapid inhibition of cdks by RA in NB leads to early cell cycle arrest, prevents neuronal differentiation, and results in a senescence-like state.
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Affiliation(s)
- L J Wainwright
- Department of Neurology, Developmental and Molecular Biology and Comprehensive Cancer Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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64
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Schrantz N, Beney GE, Auffredou MT, Bourgeade MF, Leca G, Vazquez A. The expression of p18INK4 and p27kip1 cyclin-dependent kinase inhibitors is regulated differently during human B cell differentiation. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 165:4346-52. [PMID: 11035070 DOI: 10.4049/jimmunol.165.8.4346] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Cell cycle progression is under the control of cyclin-dependent kinases (cdks), the activity of which is dependent on the expression of specific cdk inhibitors. In this paper we report that the two cdk inhibitors, p27(Kip1) and p18(INK4c), are differently expressed and control different steps of human B lymphocyte activation. Resting B cells contain large amounts of p27(Kip1) and no p18(INK4c). In vitro stimulation by Staphylococcus aureus Cowan 1 strain or CD40 ligand associated with IL-10 and IL-2 induces a rapid decrease in p27(Kip1) expression combined with cell cycle entry and progression. In contrast, in vitro Ig production correlates with specific expression of p18(INK4c) and early G(1) arrest. This G(1) arrest is associated with inhibition of cyclin D3/cdk6-mediated retinoblastoma protein phosphorylation by p18(INK4c). A similar contrasting pattern of p18(INK4c) and p27(Kip1) expression is observed both in B cells activated in vivo and in various leukemic cells. Expression of p18(INK4c) was also detected in various Ig-secreting cell lines in which both maximum Ig secretion and specific p18(INK4c) expression were observed during the G(1) phase. Our study shows that p27(Kip1) and p18(INK4c) have different roles in B cell activation; p27(Kip1) is involved in the control of cell cycle entry, and p18(INK4c) is involved in the subsequent early G(1) arrest necessary for terminal B lymphocyte differentiation.
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Affiliation(s)
- N Schrantz
- Institut National de la Santé et de la Recherche Médicale, Unité 131, and Centre de Recherche Claude Bernard, Clamart, France
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65
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Shimizu T, Awai N, Takeda K. Complex regulation of CDKs and G1 arrest during the granulocytic differentiation of human myeloblastic leukemia ML-1 cells. Oncogene 2000; 19:4640-6. [PMID: 11030153 DOI: 10.1038/sj.onc.1203821] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We previously reported that all-trans retinoic acid (ATRA) and granulocyte-macrophage colony-stimulating factor (GM-CSF) synergistically induced granulocytic differentiation in human myeloblastic leukemia ML-1 cells. The combination of these agents also suppressed DNA-synthesis. In the present study, we investigated the suppression of cyclin dependent kinase (CDK) activities resulting in G1 arrest in differentiated ML-1 cells. We show that treatment of ML-1 cells with ATRA plus GMCSF results in G1 arrest and suppression of CDK activities. Protein levels of the G1 CDKs were essentially unchanged during this time. However, we observed an increase in CDK2-bound p27 and CDK4-bound p18, and a decrease in CDK6-bound cyclin D3. These results suggest that complex regulation of CDKs play a key role in G1 arrest of ML-1 after treatment with ATRA and GM-CSF. We also showed that an increase in CDK2-bound p27 and CDK4-bound p18 are caused by treatment with ATRA and a decrease in CDK6-bound cyclin D3 is induced synergistically by treatment with both reagents. Furthermore, we propose that the changes in binding of p18 and cyclin D3 to CDKs are due to changes at the protein expression level and that the increase in p27 binding to CDK2 is due to a novel mechanism.
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Affiliation(s)
- T Shimizu
- Department of Hygiene-chemistry, Faculty of Pharmaceutical Sciences, Science University of Tokyo, Japan
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66
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Franklin DS, Godfrey VL, O'Brien DA, Deng C, Xiong Y. Functional collaboration between different cyclin-dependent kinase inhibitors suppresses tumor growth with distinct tissue specificity. Mol Cell Biol 2000; 20:6147-58. [PMID: 10913196 PMCID: PMC86090 DOI: 10.1128/mcb.20.16.6147-6158.2000] [Citation(s) in RCA: 210] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The presence of two families of seven distinct mammalian cyclin-dependent kinase (CDK) inhibitor genes is thought to mediate the complexity of connecting a variety of cellular processes to the cell cycle control pathway. The distinct pattern of tissue expression of CDK inhibitor genes suggests that they may function as tumor suppressors with different tissue specificities. To test this hypothesis, we have characterized two strains of double mutant mice lacking either p18(INK4c) and p27(KIP1) or p18(INK4c) and p21(CIP1/WAF1). Loss of both p18 and p27 function resulted in the spontaneous development by 3 months of age of at least eight different types of hyperplastic tissues and/or tumors in the pituitary, adrenals, thyroid, parathyroid, testes, pancreas, duodenum, and stomach. Six of these hyperplastic tissues and tumors were in endocrine organs, and several types of tumors routinely developed within the same animal, a phenotype reminiscent of that seen in combined human multiple endocrine neoplasia syndromes. The p18-p21 double null mice, on the other hand, developed pituitary adenomas, multifocal gastric neuroendocrine hyperplasia, and lung bronchioalveolar tumors later in life. G(1) CDK2 and CDK4 kinase activities were increased in both normal and neoplastic tissues derived from mice lacking individual CDK inhibitors and were synergistically stimulated by the simultaneous loss of two CDK inhibitors. This indicates that an increase in G(1) CDK kinase activity is a critical step during but is not sufficient for tumor growth. Our results suggest that functional collaborations between distinct CDK inhibitor genes are tissue specific and confer yet another level of regulation in cell growth control and tumor suppression.
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Affiliation(s)
- D S Franklin
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7295, USA
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67
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Chu CY, Lim RW. Involvement of p27(kip1) and cyclin D3 in the regulation of cdk2 activity during skeletal muscle differentiation. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1497:175-85. [PMID: 10903422 DOI: 10.1016/s0167-4889(00)00064-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Terminal myogenic differentiation involves an irreversible transition from a proliferative state to a post-mitotic quiescent state. We showed here that in addition to the previously reported down regulation of G(1)-related cyclin-associated kinase activities, this transition was also accompanied by an extensive reorganization of the cyclin-cdk complexes, including a dramatic shift of cdk2 from cyclin A to cyclin D3. Moreover, the inhibition of cdk activity also correlated with an increase in the expression of the p27(kip1) cdk inhibitor and in its association with the cyclin-cdk2 complexes. Since depletion of p27 substantially reduced the cdk inhibitor activity present in differentiated muscle cells, we believe that the increase in p27 expression along with the reorganization of the cyclin-cdk2 complexes may play an important role in the inhibition of cdk2 activity during the differentiation process.
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Affiliation(s)
- C Y Chu
- Department of Pharmacology, University of Missouri-Columbia, MO 65212, Columbia, USA
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68
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Latres E, Malumbres M, Sotillo R, Martín J, Ortega S, Martín-Caballero J, Flores JM, Cordón-Cardo C, Barbacid M. Limited overlapping roles of P15(INK4b) and P18(INK4c) cell cycle inhibitors in proliferation and tumorigenesis. EMBO J 2000; 19:3496-506. [PMID: 10880462 PMCID: PMC313938 DOI: 10.1093/emboj/19.13.3496] [Citation(s) in RCA: 201] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Entry of quiescent cells into the cell cycle is driven by the cyclin D-dependent kinases Cdk4 and Cdk6. These kinases are negatively regulated by the INK4 cell cycle inhibitors. We report the generation of mice defective in P15(INK4b) and P18(INK4c). Ablation of these genes, either alone or in combination, does not abrogate cell contact inhibition or senescence of mouse embryo fibroblasts in culture. However, loss of P15(INK4b), but not of P18(INK4c), confers proliferative advantage to these cells and makes them more sensitive to transformation by H-ras oncogenes. In vivo, ablation of P15(INK4b) and P18(INK4c) genes results in lymphoproliferative disorders and tumor formation. Mice lacking P18(INK4c) have deregulated epithelial cell growth leading to the formation of cysts, mostly in the cortical region of the kidneys and the mammary epithelium. Loss of both P15(INK4b) and P18(INK4c) does not result in significantly distinct phenotypic manifestations except for the appearance of cysts in additional tissues. These results indicate that P15(INK4b) and P18(IKN4c) are tumor suppressor proteins that act in different cellular lineages and/or pathways with limited compensatory roles.
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Affiliation(s)
- E Latres
- Molecular Oncology Program, Centro Nacional de Investigaciones Oncológicas Carlos III, 28220 Majadahonda, Centro Nacional de Biotecnología, CSIC, Campus Universidad Autónoma and Departamento de Patología Animal II, Facultad de Veterinar
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69
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Leshem Y, Spicer DB, Gal-Levi R, Halevy O. Hepatocyte growth factor (HGF) inhibits skeletal muscle cell differentiation: a role for the bHLH protein twist and the cdk inhibitor p27. J Cell Physiol 2000; 184:101-9. [PMID: 10825239 DOI: 10.1002/(sici)1097-4652(200007)184:1<101::aid-jcp11>3.0.co;2-d] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Hepatocyte growth factor (HGF) plays a crucial role in regulating the differentiation of both fetal and adult skeletal myoblasts. This study aimed at defining the intracellular factors that mediate the effect of HGF on adult myoblast differentiation. HGF increased Twist expression while decreasing p27(kip1) protein levels and not affecting the induction of p21(Cip1/Waf1) in satellite cells. Like HGF, overexpression of Twist did not affect p21 expression while inhibiting muscle-specific proteins. Both ectopic Twist-antisense (Twist-AS) and p27 partially rescued the effects of HGF on bromodeoxyuridine (BrdU) incorporation and myosin heavy chain (MHC) expression in muscle satellite cells; the two plasmids together effected full rescue, suggesting that HGF independently regulates these two factors to mediate its effects. Ectopic p27 promoted differentiation in the presence of HGF by blocking the induction of Twist. Using Twist-AS to lower Twist levels restored the HGF-dependent reduction of p27 and MHC. In the presence of ectopic HGF, satellite cells formed thin mononuclear myotubes. Neither ectopic p27, Twist-AS, or their combination reversed this change in cell morphology, suggesting that HGF acts through additional mediators to inhibit downstream events during myogenesis. Taken together, the results suggest that the effects of HGF on muscle cell proliferation and differentiation are mediated through changes in the expression levels of the myogenic-inhibitory basic helix-loop-helix (bHLH) protein Twist and the cell-cycle inhibitor p27.
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Affiliation(s)
- Y Leshem
- Department of Animal Sciences, The Hebrew University of Jerusalem, Rehovot, Israel
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70
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Han E, Hilsenbeck SG, Richardson A, Nelson JF. cDNA expression arrays reveal incomplete reversal of age-related changes in gene expression by calorie restriction. Mech Ageing Dev 2000; 115:157-74. [PMID: 10906510 DOI: 10.1016/s0047-6374(00)00119-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Calorie restriction (CR) extends life span and retards many age-related cellular and molecular changes in laboratory rodents. However, neither the breadth of its effects, its underlying mechanisms, nor the limits of its action is fully understood. Expression levels of 588 genes in livers from 3- and 24-month-old ad libitum-fed (AL), and 24-month-old CR (60% of AL intake) male C57BL/6J mice (four per group) were measured. Six genes met the statistical criteria for differential expression in old AL compared to young AL mice. Only one of these age-related changes was attenuated by CR. Four additional gene products, that did not change with age in AL mice, were differentially expressed in old CR compared to old AL mice. Northern and RT-PCR analyses confirmed differential expression of four of the six candidate genes identified by the array results. Many of the identified genes have not previously been reported to be affected by CR or aging. Some of the age-related changes in gene expression are consistent with an increased vulnerability of the aged liver to carcinogenic or other insults, with only partial protection against insult by CR. Incomplete reversal by CR of age-related changes in gene expression provides a potentially important path for probing the limits of CR action. These results also show the importance of independent confirmation in expression array profiling of age-related changes in gene expression.
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Affiliation(s)
- E Han
- Department of Physiology, The University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA.
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71
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Dobashi Y, Shoji M, Kitagawa M, Noguchi T, Kameya T. Simultaneous suppression of cdc2 and cdk2 activities induces neuronal differentiation of PC12 cells. J Biol Chem 2000; 275:12572-80. [PMID: 10777547 DOI: 10.1074/jbc.275.17.12572] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The involvement of cdc2 and cdk2 during neuronal differentiation in rat pheochromocytoma PC12 cells was examined. When PC12 cells were cultured with nerve growth factor (NGF), expression of cdc2 decreased significantly after day 5, while expression of cdk2 decreased gradually after day 7. Cells overexpressing cdc2 or cdk2 were resistant to NGF-induced differentiation and growth suppression, and maintained high cdc2 or cdk2 kinase activity, respectively, during NGF treatment. In contrast, the NGF-treated parental cells showed a marked decline in these kinase activities after day 3. When PC12 cells were treated with specific inhibitors of cdc2/cdk2 (butyrolactone-I, olomoucin), they showed marked neurite extension and up-regulation of microtubule-associated protein 2 expression. In addition, treatment with mixtures of antisense oligonucleotides for cdc2 and cdk2 resulted in down-regulation of both cdc2 and cdk2 kinase activities as well as significant neurite outgrowth and up-regulation of microtubule-associated protein 2 expression. However, neurite outgrowth was not observed in cells treated with either single antisense oligonucleotide, or antisense cdc2 + cdk4 or cdk2 + cdk4 oligonucleotide mixtures. These results suggest that simultaneous down-regulation of cdc2 and cdk2 activity is sufficient and necessary for neuronal differentiation in PC12 cells.
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Affiliation(s)
- Y Dobashi
- Department of Pathology, Kitasato University School of Medicine, 1-15-1, Kitasato, Sagamihara, Kanagawa 228-8555, Japan.
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72
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Mal A, Chattopadhyay D, Ghosh MK, Poon RY, Hunter T, Harter ML. p21 and retinoblastoma protein control the absence of DNA replication in terminally differentiated muscle cells. J Cell Biol 2000; 149:281-92. [PMID: 10769022 PMCID: PMC2175169 DOI: 10.1083/jcb.149.2.281] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/1999] [Accepted: 03/10/2000] [Indexed: 01/10/2023] Open
Abstract
During differentiation, skeletal muscle cells withdraw from the cell cycle and fuse into multinucleated myotubes. Unlike quiescent cells, however, these cells cannot be induced to reenter S phase by means of growth factor stimulation. The studies reported here document that both the retinoblastoma protein (Rb) and the cyclin-dependent kinase (cdk) inhibitor p21 contribute to this unresponsiveness. We show that the inactivation of Rb and p21 through the binding of the adenovirus E1A protein leads to the induction of DNA replication in differentiated muscle cells. Moreover, inactivation of p21 by E1A results in the restoration of cyclin E-cdk2 activity, a kinase made nonfunctional by the binding of p21 and whose protein levels in differentiated muscle cells is relatively low in amount. We also show that restoration of kinase activity leads to the phosphorylation of Rb but that this in itself is not sufficient for allowing differentiated muscle cells to reenter the cell cycle. All the results obtained are consistent with the fact that Rb is functioning downstream of p21 and that the activities of these two proteins may be linked in sustaining the postmitotic state.
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Affiliation(s)
- Asoke Mal
- Department of Molecular Biology, Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, Ohio 44195
| | - Debasis Chattopadhyay
- Department of Molecular Biology, Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, Ohio 44195
| | - Mrinal K. Ghosh
- Department of Molecular Biology, Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, Ohio 44195
| | - Randy Y.C. Poon
- Department of Biochemistry, The Hong Kong University of Science and Technology, Kowloon, Hong Kong
| | - Tony Hunter
- The Salk Institute, La Jolla, California 92037
| | - Marian L. Harter
- Department of Molecular Biology, Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, Ohio 44195
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73
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Swarbrick A, Lee CS, Sutherland RL, Musgrove EA. Cooperation of p27(Kip1) and p18(INK4c) in progestin-mediated cell cycle arrest in T-47D breast cancer cells. Mol Cell Biol 2000; 20:2581-91. [PMID: 10713180 PMCID: PMC85474 DOI: 10.1128/mcb.20.7.2581-2591.2000] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/1999] [Accepted: 01/10/2000] [Indexed: 02/07/2023] Open
Abstract
The steroid hormone progesterone regulates proliferation and differentiation in the mammary gland and uterus by cell cycle phase-specific actions. The long-term effect of progestins on T-47D breast cancer cells is inhibition of cellular proliferation. This is accompanied by decreased G(1) cyclin-dependent kinase (CDK) activities, redistribution of the CDK inhibitor p27(Kip1) among these CDK complexes, and alterations in the elution profile of cyclin E-Cdk2 upon gel filtration chromatography, such that high-molecular-weight complexes predominate. This study aimed to determine the relative contribution of CDK inhibitors to these events. Following progestin treatment, the majority of cyclin E- and D-CDK complexes were bound to p27(Kip1) and few were bound to p21(Cip1). In vitro, recombinant His(6)-p27 could quantitatively reproduce the effects on cyclin E-Cdk2 kinase activity and the shift in molecular weight observed following progestin treatment. In contrast, cyclin D-Cdk4 was not inhibited by His(6)-p27 in vitro or p27(Kip1) in vivo. However, an increase in the expression of the Cdk4/6 inhibitor p18(INK4c) and its extensive association with Cdk4 and Cdk6 were apparent following progestin treatment. Recombinant p18(INK4c) led to the reassortment of cyclin-CDK-CDK inhibitor complexes in vitro, with consequent decrease in cyclin E-Cdk2 activity. These results suggest a concerted model of progestin action whereby p27(Kip1) and p18(INK4c) cooperate to inhibit cyclin E-Cdk2 and Cdk4. Since similar models have been developed for growth inhibition by transforming growth factor beta and during adipogenesis, interaction between the Cip/Kip and INK4 families of inhibitors may be a common theme in physiological growth arrest and differentiation.
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Affiliation(s)
- A Swarbrick
- Cancer Research Program, Garvan Institute of Medical Research, St. Vincent's Hospital, Sydney, New South Wales 2010, Australia
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74
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Thullberg M, Bartkova J, Khan S, Hansen K, Rönnstrand L, Lukas J, Strauss M, Bartek J. Distinct versus redundant properties among members of the INK4 family of cyclin-dependent kinase inhibitors. FEBS Lett 2000; 470:161-6. [PMID: 10734227 DOI: 10.1016/s0014-5793(00)01307-7] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
p16(INK4a), p15(INK4b), p18(INK4c) and p19(INK4d) comprise a family of cyclin-dependent kinase inhibitors and tumor suppressors. We report that the INK4 proteins share the ability to arrest cells in G1, and interact with CDK4 or CDK6 with similar avidity. In contrast, only p18 and particularly p19 are phosphorylated in vivo, and each of the human INK4 proteins shows unique expression patterns dependent on cell and tissue type, and differentiation stage. Thus, the INK4 proteins harbor redundant as well as non-overlapping properties, suggesting distinct regulatory modes, and diverse roles for the individual INK4 family members in cell cycle control, cellular differentiation, and multistep oncogenesis.
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Affiliation(s)
- M Thullberg
- Institute of Cancer Biology, Danish Cancer Society, Strandboulevarden 49, DK-2100, Copenhagen, Denmark
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75
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Affiliation(s)
- M F Roussel
- Department of Tumor Cell Biology, St Jude Children's Research Hospital, 322 North Lauderdale, Memphis, Tennessee, TN 38105, USA
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76
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Morrison RF, Farmer SR. Role of PPARgamma in regulating a cascade expression of cyclin-dependent kinase inhibitors, p18(INK4c) and p21(Waf1/Cip1), during adipogenesis. J Biol Chem 1999; 274:17088-97. [PMID: 10358062 DOI: 10.1074/jbc.274.24.17088] [Citation(s) in RCA: 232] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Molecular mechanisms coupling growth arrest and cell differentiation were examined during adipogenesis. Data are presented that document a cascade expression of members of two independent families of cyclin-dependent kinase inhibitors that define distinct states of growth arrest during 3T3-L1 preadipocyte differentiation. Exit from the cell cycle into a pre-differentiation state of post-mitotic growth arrest was characterized by significant increases in p21 and p27. During onset of irreversible growth arrest associated with terminal differentiation, the level of p21 declined with a concomitant, dramatic increase in p18 and a sustained level of p27. The expression of p18 and p21, regulated at the level of protein and mRNA accumulation, was directly coupled to differentiation. Stable cell lines were engineered to express adipogenic transcription factors to examine the active role of trans-acting elements in regulating these cell cycle inhibitors. Ectopic expression of peroxisome proliferator-activated receptor (PPAR) gamma in non-precursor fibroblastic cell lines resulted in conversion to adipocytes and a coordinated increase in p18 and p21 mRNA and protein expression in a PPARgamma ligand-associated manner. These data demonstrate a role for PPARgamma in mediating the differentiation-dependent cascade expression of cyclin-dependent kinase inhibitors, thereby providing a molecular mechanism coupling growth arrest and adipocyte differentiation.
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Affiliation(s)
- R F Morrison
- Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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77
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Abstract
Space travel and extending human lifespan are two of the many advances of the twentieth century. However, both of these scientific wonders exact a price for their gains; i.e. deleterious effects on normal physiological processes. For example, both old age and prolonged microgravity travel are associated with atrophy in heart, muscle, and bone. The underlying signal transduction pathways, the control mechanisms for the processes of proliferation, differentiation, and apoptosis, may prove to be similarly altered in both old age and microgravity travel. We suggest that the mechanical events involved in space travel provide a telescopic compression of lifespan changes in these tissues; if so, space travel provides an excellent opportunity to investigate how long-term degeneration occurs on Earth. With the aid of biochip technology for multi-factorial analysis, a platform can be generated to create therapeutic modalities to contain, retard, reduce, or prevent this tissue atrophy, either in space or on Earth.
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Affiliation(s)
- E Wang
- The Bloomfield Center For Research in Aging, Lady Davis Institute for Medical Research, Montréal, Québec, Canada
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78
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Tian JQ, Quaroni A. Involvement of p21(WAF1/Cip1) and p27(Kip1) in intestinal epithelial cell differentiation. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:C1245-58. [PMID: 10362586 DOI: 10.1152/ajpcell.1999.276.6.c1245] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Using the conditionally immortalized human cell line tsFHI, we have investigated the role of cyclin-dependent kinase inhibitors (CKIs) in intestinal epithelial cell differentiation. Expression of cyclins, cyclin-dependent kinases (Cdk), and CKIs was examined under conditions promoting growth, growth arrest, or expression of differentiated traits. Formation of complexes among cell cycle regulatory proteins and their kinase activities were also investigated. The tsFHI cells express three CKIs: p16, p21, and p27. With differentiation, p21 and p27 were strongly induced, but with different kinetics: the p21 increase was rapid but transient and the p27 increase was delayed but sustained. Our results suggest that the function of p16 is primarily to inhibit cyclin D-associated kinases, making tsFHI cells dependent on cyclin E-Cdk2 for pRb phosphorylation and G1/S progression. Furthermore, they indicate that p21 is the main CKI involved in irreversible growth arrest during the early stages of cell differentiation in association with D-type cyclins, cyclin E, and Cdk2, whereas p27 may induce or stabilize expression of differentiated traits acting independently of cyclin-Cdk function.
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Affiliation(s)
- J Q Tian
- Section of Physiology, Cornell University, Ithaca, New York 14853, USA
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79
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Studzinski GP, Harrison LE. Differentiation-related changes in the cell cycle traverse. INTERNATIONAL REVIEW OF CYTOLOGY 1999; 189:1-58. [PMID: 10333577 DOI: 10.1016/s0074-7696(08)61384-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
This review examines recent developments relating to the interface between cell proliferation and differentiation. It is suggested that the mechanism responsible for this transition is more akin to a "dimmer" than to a "switch," that it is more useful to refer to early and late stages of differentiation rather than to "terminal" differentiation, and examples of the reversibility of differentiation are provided. An outline of the established paradigm of cell cycle regulation is followed by summaries of recent studies that suggest that this paradigm is overly simplified and should be interpreted in the context of different cell types. The role of inhibitors of cyclin-dependent kinases in differentiation is discussed, but the data are still inconclusive. An increasing interest in the changes in G2/M transition during differentiation is illustrated by examples of polyploidization during differentiation, such as megakaryocyte maturation. Although the retinoblastoma protein is currently maintaining its prominent role in control of proliferation and differentiation, it is anticipated that equally important regulators will be discovered and provide an explanation at the molecular level for the gradual transition from proliferation to differentiation.
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Affiliation(s)
- G P Studzinski
- Department of Pathology and Laboratory Medicine, University of Medicine and Dentistry, New Jersey Medical School, Newark 07103, USA
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80
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Subcellular and Cell-Cycle Expression Profiles of CDK-Inhibitors in Normal Differentiating Myeloid Cells. Blood 1999. [DOI: 10.1182/blood.v93.9.2907] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
A central question in hematopoiesis is how cell-cycling behavior changes during the emergence of the differentiated state. To further understand what genetic regulators might couple proliferation status to differentiation, we studied the expression of the cell-cycle inhibitors p21 and p27 during the in vitro differentiation of normal CD34+ blast cells along the myeloid lineage. We find p27 but not p21 to be expressed in freshly harvested resting CD34+ cells. Thereafter, p21 levels peak concurrent with cellular proliferation and then decline in expression as cells undergo terminal differentiation. In contrast, p27 levels are fairly constant but the subcellular localization of p27 changes from nuclear expression to predominantly cytoplasmic expression and finally to perinuclear localization at progressive stages of differentiation. This report discusses the implications of these findings.
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81
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Abstract
A central question in hematopoiesis is how cell-cycling behavior changes during the emergence of the differentiated state. To further understand what genetic regulators might couple proliferation status to differentiation, we studied the expression of the cell-cycle inhibitors p21 and p27 during the in vitro differentiation of normal CD34+ blast cells along the myeloid lineage. We find p27 but not p21 to be expressed in freshly harvested resting CD34+ cells. Thereafter, p21 levels peak concurrent with cellular proliferation and then decline in expression as cells undergo terminal differentiation. In contrast, p27 levels are fairly constant but the subcellular localization of p27 changes from nuclear expression to predominantly cytoplasmic expression and finally to perinuclear localization at progressive stages of differentiation. This report discusses the implications of these findings.
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82
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Cuenda A, Cohen P. Stress-activated protein kinase-2/p38 and a rapamycin-sensitive pathway are required for C2C12 myogenesis. J Biol Chem 1999; 274:4341-6. [PMID: 9933636 DOI: 10.1074/jbc.274.7.4341] [Citation(s) in RCA: 269] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The differentiation of C2C12 myoblasts to myotubes was found to be accompanied by a strong activation of p70 S6 kinase and the mitogen-activated protein kinase (MAPK) family member SAPK2/p38, without significant activation of p42 MAPK and only slight activation of SAPK1/JNK and protein kinase Balpha. Consistent with these findings, SB 203580 (a specific inhibitor of SAPK2/p38) or rapamycin (which blocks the activation of p70 S6 kinase) prevented the formation of multinucleated myotubes, as well as the expression of muscle-specific proteins that included SAPK3 (another MAPK family member). PD 098059 (which prevents the activation of p42 MAPK) had no effect on myotube formation. Surprisingly, the slow activation of p70 S6 kinase during differentiation was not only prevented by rapamycin but also by SB 203580, and the activation of MAPKAP kinase-2 (an in vivo substrate of SAPK2/p38) was not only prevented by SB 203580 but also by rapamycin. In contrast, the acute activation of p70 S6 kinase in C2C12 myoblasts induced by phorbol esters was unaffected by SB 203580 and the acute activation of MAPKAP kinase-2 induced by anisomycin was unaffected by rapamycin. These results show for the first time that SAPK2/p38 plays an essential role in C2C12 cell differentiation.
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Affiliation(s)
- A Cuenda
- MRC Protein Phosphorylation Unit, Department of Biochemistry, University of Dundee, MSI/WTB Complex, Dow Street, Dundee DD1 5EH, United Kingdom.
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83
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Ruas M, Peters G. The p16INK4a/CDKN2A tumor suppressor and its relatives. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1378:F115-77. [PMID: 9823374 DOI: 10.1016/s0304-419x(98)00017-1] [Citation(s) in RCA: 338] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- M Ruas
- Imperial Cancer Research Fund, London, UK
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84
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Abstract
The selective degradation of many short-lived proteins in eukaryotic cells is carried out by the ubiquitin system. In this pathway, proteins are targeted for degradation by covalent ligation to ubiquitin, a highly conserved small protein. Ubiquitin-mediated degradation of regulatory proteins plays important roles in the control of numerous processes, including cell-cycle progression, signal transduction, transcriptional regulation, receptor down-regulation, and endocytosis. The ubiquitin system has been implicated in the immune response, development, and programmed cell death. Abnormalities in ubiquitin-mediated processes have been shown to cause pathological conditions, including malignant transformation. In this review we discuss recent information on functions and mechanisms of the ubiquitin system. Since the selectivity of protein degradation is determined mainly at the stage of ligation to ubiquitin, special attention is focused on what we know, and would like to know, about the mode of action of ubiquitin-protein ligation systems and about signals in proteins recognized by these systems.
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Affiliation(s)
- A Hershko
- Unit of Biochemistry, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
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85
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Franklin DS, Godfrey VL, Lee H, Kovalev GI, Schoonhoven R, Chen-Kiang S, Su L, Xiong Y. CDK inhibitors p18(INK4c) and p27(Kip1) mediate two separate pathways to collaboratively suppress pituitary tumorigenesis. Genes Dev 1998; 12:2899-911. [PMID: 9744866 PMCID: PMC317173 DOI: 10.1101/gad.12.18.2899] [Citation(s) in RCA: 294] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/1998] [Accepted: 07/31/1998] [Indexed: 11/25/2022]
Abstract
INK4 and CIP/KIP are two distinct families of cyclin-dependent kinase (CDK) inhibitors implicated in mediating a wide range of cell growth control signals. We have created p18(INK4c)-deficient mice. These mice develop gigantism and widespread organomegaly. The pituitary gland, spleen, and thymus are disproportionately enlarged and hyperplastic. T and B lymphocytes develop normally in p18-deficient mice, but both exhibit increased cellularity and a higher proliferative rate upon mitogenic stimulation. Loss of p18, like that of p27, but not other CDK inhibitor genes, leads to a gradual progression from intermediate lobe pituitary hyperplasia in young mice to an adenoma by 10 months of age with a nearly complete penetrance. Mice lacking both p18 and p27, like mice chimeric for Rb deficiency, invariably died from pituitary adenomas by 3 months. Hence, p18 and p27 mediate two separate pathways to collaboratively suppress pituitary tumorigenesis, likely by controlling the function of Rb.
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Affiliation(s)
- D S Franklin
- Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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86
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Soos TJ, Park M, Kiyokawa H, Koff A. Regulation of the cell cycle by CDK inhibitors. Results Probl Cell Differ 1998; 22:111-31. [PMID: 9670321 DOI: 10.1007/978-3-540-69686-5_5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- T J Soos
- Program in Molecular Biology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA
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87
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Watanabe G, Pena P, Shambaugh GE, Haines GK, Pestell RG. Regulation of cyclin dependent kinase inhibitor proteins during neonatal cerebella development. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1998; 108:77-87. [PMID: 9693786 DOI: 10.1016/s0165-3806(98)00032-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The cyclin dependent kinase holoenzymes (CDKs), composed of catalytic (cdk) and regulatory (cyclin) subunits, promote cellular proliferation and are inhibited by cyclin dependent kinase inhibitor proteins (CDKIs). The CDKIs include the Ink4 family (p15Ink4b, p16Ink4a, p18Ink4c, p19Ink4d) and the KIP family (p21Cip1 and p27Kip1). The sustained induction of p21 and p18 during myogenesis implicates these CDKI in maintaining cellular differentiation. Herein we examined the CDK (cyclin D1, cdk5) and CDKI expression profiles during the first 24 days of postnatal rat cerebella development. Cdk5 abundance increased and cyclin D1 decreased from day 9 through to adulthood. The CDKIs increased transiently during differentiation. p27 increased 20-fold between days 4 and 24, whereas p21 rose twofold between 6 to 11 days. p19, p18 and p16 increased approximately two- to threefold, falling to low levels in the adult. Immunostaining of cyclin D1 was localized in the external granular cells, whereas p27, was found primarily in the Purkinje cells. The period of maximal differentiation between days 9 to 13 was associated with a change in p21 and p16 staining from the external granular and Purkinje cells to a primarily Purkinje cell distribution. Protein-calorie malnutrition, which was previously shown to arrest rat cerebella development, reduced cyclin D1 kinase activity and p27 levels. However, p16 and p21 levels were unchanged. We conclude that the CDKIs are induced with distinct kinetics in specific cell types and respond differentially to growth factors during cerebella development, suggesting discrete roles for these proteins in normal cerebella development.
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Affiliation(s)
- G Watanabe
- Albert Einstein Cancer Center, Department of Medicine, Bronx, NY 10461, USA
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88
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Blais A, Labrie Y, Pouliot F, Lachance Y, Labrie C. Structure of the gene encoding the human cyclin-dependent kinase inhibitor p18 and mutational analysis in breast cancer. Biochem Biophys Res Commun 1998; 247:146-53. [PMID: 9636670 DOI: 10.1006/bbrc.1998.8497] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The cyclin-dependent kinase (CDK) inhibitor p18 blocks progression of the cell cycle by associating with the cyclin D-dependent kinases CDK6 and CDK4. To better understand the regulation of p18 gene expression, we isolated full-length cDNA clones from a human BT-20 breast cancer cell cDNA library. These clones were then used to isolate the human gene from a human genomic DNA library. The human p18 gene spans at least 7.5 kb and is composed of three exons, two of which encode the p18 protein. The genomic clone we isolated contained 5 kb of putative promotor sequence which directed expression of the luciferase reporter gene in transient transfection experiments. The longest cDNA that we isolated from BT-20 cells contained 2103 nucleotides which corresponds to the size of the major RNA transcript detected by Northern analysis in these cells. Transcription start sites mapping to the 5' end of the putative full-length cDNA were identified by ribonuclease protection assays. A novel polymorphism was identified in the 3' untranslated region of BT-20 cell cDNA clones that contained the previously described codon 72 mutation. The codon 72 mutation was also detected in 3 of 35 breast tumors analyzed using a mismatch PCR/RFLP strategy.
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Affiliation(s)
- A Blais
- Laboratory of Molecular Endocrinology, CHUL Research Center, University Hospital of Quebec, Canada
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89
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Arora T, Jelinek DF. Differential myeloma cell responsiveness to interferon-alpha correlates with differential induction of p19(INK4d) and cyclin D2 expression. J Biol Chem 1998; 273:11799-805. [PMID: 9565604 DOI: 10.1074/jbc.273.19.11799] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Interferon-alpha (IFN-alpha) has been used as therapy for the treatment of a variety of viral diseases and malignancies including multiple myeloma. The effectiveness of interferon-alpha in treating multiple myeloma, however, has been somewhat variable, and the mechanism(s) accounting for this is not well understood. As a means to examine the basis for the differential effectiveness of this cytokine, we have analyzed IFN-alpha-mediated modulation of the cell cycle in two human myeloma cell lines. These two cell lines, ANBL-6 and KAS-6/1, display dramatically different outcomes in response to this cytokine. Although IFN-alpha inhibited the growth of ANBL-6 cells by blocking cell cycle progression from G0/G1 to S phase, IFN-alpha stimulated cell cycle progression in KAS-6/1 cells. Moreover, the effects of IFN-alpha on cell cycle progression correlated with the phosphorylation status of the retinoblastoma protein. Of interest, IFN-alpha increased cyclin D2 expression and cyclin-dependent kinase activity in the KAS-6/1 cells but not in the ANBL-6 cells. To determine whether the differential effects of IFN-alpha on myeloma cell cycle progression could also result from differences in the expression of cyclin-dependent kinase inhibitors, we examined the effects of IFN-alpha on the induction of cyclin-dependent kinase inhibitors with broad regulatory function (p21 and p27) and those with specificity for G1-associated cyclin-cyclin-dependent kinase complexes (p15, p16, p18, and p19). Although we failed to detect an effect of IFN-alpha on expression levels of p21, p15, p16, or p18, IFN-alpha treatment of the ANBL-6 cell line resulted in induction of p19 expression, whereas it was without effect on the KAS-6/1 cell line. These results suggest that heterogeneity in IFN-alpha-mediated growth effects in myeloma cells correlates with differential induction of cyclin D2 and p19(INK4d) expression.
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Affiliation(s)
- T Arora
- Department of Immunology, Mayo Clinic/Foundation, Rochester, Minnesota 55905, USA
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90
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Walsh K. Coordinate regulation of cell cycle and apoptosis during myogenesis. PROGRESS IN CELL CYCLE RESEARCH 1998; 3:53-8. [PMID: 9552406 DOI: 10.1007/978-1-4615-5371-7_5] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
During myogenesis, precursor cells irreversibly withdraw from the cell cycle as they differentiate into mature myotubes. The state of myocyte differentiation also influences the propensity of these cells to undergo apoptosis. Proliferative precursor cells are far more susceptible to apoptotic cell death than are terminally differentiated myotubes. The upregulation of the cdk inhibitor p21 and the dephosphorylation of pRb are critical regulatory events that establish both the post-mitotic and apoptosis-resistant states. The coordinate regulation of cell proliferation and death provides the organism with a mechanism to control the deposition of muscle mass during embryonic development.
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Affiliation(s)
- K Walsh
- Division of Cardiovascular Research, St. Elizabeth's Medical Center, Boston, MA, USA
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91
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Englaro W, Bertolotto C, Buscà R, Brunet A, Pagès G, Ortonne JP, Ballotti R. Inhibition of the mitogen-activated protein kinase pathway triggers B16 melanoma cell differentiation. J Biol Chem 1998; 273:9966-70. [PMID: 9545341 DOI: 10.1074/jbc.273.16.9966] [Citation(s) in RCA: 157] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In B16 melanoma cells, mitogen-activated protein (MAP) kinases are activated during cAMP-induced melanogenesis (Englaro, W., Rezzonico, R., Durand-Clément, M., Lallemand, D., Ortonne, J. P., and Ballotti, R. (1995) J. Biol. Chem. 270, 24315-24320). To establish the role of the MAP kinases in melanogenesis, we studied the effects of a specific MAP kinase kinase (MEK) inhibitor PD 98059 on different melanogenic parameters. We showed that PD 98059 inhibits the activation of MAP kinase extracellular signal-regulated kinase 1 by cAMP, but does not impair the effects of cAMP either on the morphological differentiation, characterized by an increase in dendrite outgrowth, or on the up-regulation of tyrosinase that is the key enzyme in melanogenesis. On the contrary, PD 98059 promotes by itself cell dendricity and increases the tyrosinase amount and activity. Moreover, down-regulation of the MAP kinase pathway by PD 98059, or with dominant negative mutants of p21(ras) and MEK, triggers a stimulation of the tyrosinase promoter activity and enhances the effect of cAMP on this parameter. Conversely, activation of the MAP kinase pathway, using constitutive active mutants of p21(ras) and MEK, leads to an inhibition of basal and cAMP-induced tyrosinase gene transcription. These results demonstrate that the MAP kinase pathway activation is not required for cAMP-induced melanogenesis. Furthermore, the inhibition of this pathway induces B16 melanoma cell differentiation, while a sustained activation impairs the melanogenic effect of cAMP-elevating agents.
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Affiliation(s)
- W Englaro
- INSERM U-385, Faculté de médecine, Avenue de Valombrose, 06107 Nice Cedex 2, France
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92
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Abstract
Depletion of guanine nucleotide pools after inhibition of inosine monophosphate dehydrogenase (IMPDH) potently inhibits DNA synthesis by arresting cells in G1 and has been shown to induce the differentiation of cultured myeloid and erythroid cell lines, as well as chronic granulocytic leukemic cells after blast transformation. Inhibitors of IMPDH are also highly effective as immunosuppressive agents. The mechanism underlying these pleiotropic effects of depletion of guanine nucleotides is unknown. We have examined the effects of mycophenolic acid (MPA), a potent IMPDH inhibitor, on the cell cycle progression of activated normal human T lymphocytes. MPA treatment resulted in the inhibition of pRb phosphorylation and cell entry into S phase. The expression of cyclin D3, a major component of the cyclin-dependent kinase (CDK) activity required for pRb phosphorylation, was completely abrogated by MPA treatment of T cells activated by interleukin-2 (IL-2) and leucoagglutinin (PHA-L), whereas the expression of cyclin D2, CDK6, and CDK4 was more mildly attenuated. The direct kinase activity of a complex immunoprecipitated with anti-CDK6 antibody was also inhibited. In addition, MPA prevented the IL-2–induced elimination of p27Kip1, a CDK inhibitor, and resulted in the retention of high levels of p27Kip1 in IL-2/PHA-L–treated T cells bound to CDK2. These results indicate that inhibition of the de novo synthesis of guanine nucleotides blocks the transition of normal peripheral blood T lymphocytes from G0 to S phase in early- to mid-G1 and that this cell cycle arrest results from inhibition of the induction of cyclin D/CDK6 kinase and the elimination of p27Kip1 inhibitory activity.
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93
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Phelps DE, Hsiao KM, Li Y, Hu N, Franklin DS, Westphal E, Lee EY, Xiong Y. Coupled transcriptional and translational control of cyclin-dependent kinase inhibitor p18INK4c expression during myogenesis. Mol Cell Biol 1998; 18:2334-43. [PMID: 9528803 PMCID: PMC121487 DOI: 10.1128/mcb.18.4.2334] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/1997] [Accepted: 01/22/1998] [Indexed: 02/07/2023] Open
Abstract
Terminal differentiation of many cell types involves permanent withdrawal from the cell division cycle. The p18INK4c protein, a member of the p16/INK4 cyclin-dependent kinase (CDK) inhibitor family, is induced more than 50-fold during myogenic differentiation of mouse C2C12 myoblasts to become the predominant CDK inhibitor complexed with CDK4 and CDK6 in terminally differentiated myotubes. We have found that the p18INK4c gene expresses two mRNA transcripts--a 2.4-kb transcript, p18(L), and a 1.2-kb transcript, p18(S). In proliferating C2C12 myoblasts, only the larger p18(L) transcript is expressed from an upstream promoter. As C2C12 cells are induced to differentiate into permanently arrested myotubes, the abundance of the p18(L) transcript decreases. The smaller p18(S) transcript expressed from a downstream promoter becomes detectable by 12 h postinduction and is the predominant transcript expressed in terminally differentiated myotubes. Both transcripts contain coding exons 2 and 3, but p18(L) uniquely contains an additional noncoding 1.2-kb exon, exon 1, corresponding exclusively to the 5' untranslated region (5' UTR). The expression pattern of the shorter p18(S) transcript, but not that of the longer p18(L) transcript, correlates with terminal differentiation of muscle, lung, liver, thymus, and eye lens cells during mouse embryo development. The presence of the long 5' UTR in exon 1 attenuated the translation of p18(L) transcript, while its absence from the shorter p18(S) transcript resulted in significantly more efficient translation of the p18 protein. Our results demonstrate that during terminal muscle cell differentiation, induction of the p18 protein is regulated by promoter switching coupled with translational control.
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Affiliation(s)
- D E Phelps
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, 27599-3280, USA
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94
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Affiliation(s)
- A Carnero
- Cold Spring Harbor Laboratory, NY 11724, USA
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95
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Affiliation(s)
- J P Brockes
- Ludwig Institute for Cancer Research, University College London, UK.
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96
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McDonald NQ, Peters G. Ankyrin for clues about the function of p16INK4a. NATURE STRUCTURAL BIOLOGY 1998; 5:85-8. [PMID: 9461066 DOI: 10.1038/nsb0298-85] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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97
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Abstract
Myogenic precursor cells withdraw irreversibly from the cell cycle as they differentiate into mature myotubes. Cell cycle exit occurs early during the differentiation program and is required for normal expression of the contractile phenotype. Differentiated myocytes also display a decreased propensity to undergo apoptotic cell death. The upregulation of the cyclin-dependent kinase inhibitor p21 and the dephosphorylation of retinoblastoma protein (pRb) appear to be critical regulatory events for the establishment of both the postmitotic and apoptosis-resistant states. The coordinated regulation of cell proliferation and death provides the developing embryo with a mechanism for controlling muscle mass and thereby the size of individual motor units.
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Affiliation(s)
- K Walsh
- Division of Cardiovascular Research, St Elizabeth's Medical Center, Tufts University School of Medicine, Boston, Massachusetts, USA.
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98
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Wang ZF, Sirotkin AM, Buchold GM, Skoultchi AI, Marzluff WF. The mouse histone H1 genes: gene organization and differential regulation. J Mol Biol 1997; 271:124-38. [PMID: 9300059 DOI: 10.1006/jmbi.1997.1166] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
There are six mouse histone H1 genes present in the histone gene cluster on mouse chromosome 13. These genes encode five histone H1 variants expressed in somatic cells, H1a to H1e, and the testis-specific H1t histone. Two of the genes that have not been assigned previously to the five somatic H1 subtypes have been identified as encoding the H1b and H1d subtypes. Three of the H1 genes, H1a, H1c and H1t, are present on an 80 kb segment of DNA that contains nine core histone genes. Two others, H1d and H1e, are present in a second patch, while the H1b gene is at least 500 kb away in a patch containing 14 core histone genes. The histone H1 genes are differentially expressed. All five genes for the somatic histone H1 proteins are expressed in exponentially growing cells. However, the levels of H1a, H1b and H1d mRNAs are greatly reduced in cells that are terminally differentiated or arrested in G0, while the H1c and H1e mRNAs continue to be expressed. In addition to the major RNA that ends at the stem-loop, the H1c gene expresses a longer, polyadenylated mRNA in differentiated cells, although in varying amounts. None of the other histone H1 genes encodes detectable amounts of polyadenylated mRNAs.
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Affiliation(s)
- Z F Wang
- Department of Biology, University of North Carolina at Chapel Hill 27599, USA
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99
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Features of Macrophage Differentiation Induced by p19INK4d, a Specific Inhibitor of Cyclin D–Dependent Kinases. Blood 1997. [DOI: 10.1182/blood.v90.1.126] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
AbstractThe mitogen-dependent induction of cyclin D–dependent kinase activity is required for cells to enter the DNA synthetic (S) phase of their division cycle. Immature 32Dcl3 myeloid cells (32D) proliferating in the presence of interleukin-3 (IL-3) normally express cyclins D2 and D3, which assemble into binary holoenzyme complexes with their catalytic subunits, CDK4 and CDK6. When 32D cells are switched to medium containing granulocyte colony-stimulating factor (G-CSF ) instead of IL-3, D-type cyclins are degraded and, in the absence of their associated kinase activity, the cells arrest in the first gap phase (G1 ) of the cell cycle and differentiate to neutrophils. We derived 32D cells in which the expression of p19INK4d, a specific polypeptide inhibitor of CDK4 and CDK6, is regulated by the heavy metal-inducible sheep metallothionein promoter. Induction of p19INK4d in response to zinc prolonged cell survival in the absence of growth factor treatment. When maintained in medium containing both IL-3 and zinc, these cells lost cyclin D–dependent kinase activity, underwent G1 phase arrest, and acquired certain morphologic, antigenic, and functional properties of mononuclear phagocytes. Cells induced to express p19INK4d did not synthesize receptors for macrophage colony-stimulating factor (M-CSF/CSF-1) and reverted to an immature myeloid phenotype when shifted back into medium containing IL-3 alone. These cells exhibited accelerated differentiation to neutrophils in response to G-CSF but also gave rise to macrophage-like cells when maintained in medium containing both G-CSF and zinc. Therefore, the acquisition of macrophage properties in response to zinc treatment neither depended upon IL-3 nor upon G1 phase arrest per se and instead reflects some ability of p19INK4d, and presumably cyclin D–dependent kinases, to affect myeloid differentiation.
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100
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Features of Macrophage Differentiation Induced by p19INK4d, a Specific Inhibitor of Cyclin D–Dependent Kinases. Blood 1997. [DOI: 10.1182/blood.v90.1.126.126_126_137] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The mitogen-dependent induction of cyclin D–dependent kinase activity is required for cells to enter the DNA synthetic (S) phase of their division cycle. Immature 32Dcl3 myeloid cells (32D) proliferating in the presence of interleukin-3 (IL-3) normally express cyclins D2 and D3, which assemble into binary holoenzyme complexes with their catalytic subunits, CDK4 and CDK6. When 32D cells are switched to medium containing granulocyte colony-stimulating factor (G-CSF ) instead of IL-3, D-type cyclins are degraded and, in the absence of their associated kinase activity, the cells arrest in the first gap phase (G1 ) of the cell cycle and differentiate to neutrophils. We derived 32D cells in which the expression of p19INK4d, a specific polypeptide inhibitor of CDK4 and CDK6, is regulated by the heavy metal-inducible sheep metallothionein promoter. Induction of p19INK4d in response to zinc prolonged cell survival in the absence of growth factor treatment. When maintained in medium containing both IL-3 and zinc, these cells lost cyclin D–dependent kinase activity, underwent G1 phase arrest, and acquired certain morphologic, antigenic, and functional properties of mononuclear phagocytes. Cells induced to express p19INK4d did not synthesize receptors for macrophage colony-stimulating factor (M-CSF/CSF-1) and reverted to an immature myeloid phenotype when shifted back into medium containing IL-3 alone. These cells exhibited accelerated differentiation to neutrophils in response to G-CSF but also gave rise to macrophage-like cells when maintained in medium containing both G-CSF and zinc. Therefore, the acquisition of macrophage properties in response to zinc treatment neither depended upon IL-3 nor upon G1 phase arrest per se and instead reflects some ability of p19INK4d, and presumably cyclin D–dependent kinases, to affect myeloid differentiation.
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