PTB-associated splicing factor regulates growth factor-stimulated gene expression in mammalian cells

An insulin-like growth factor I (IGF-I) response element (IGFRE) in the porcine P-450 cholesterol side-chain cleavage gene (P450scc) binds two transcription factors, Sp1 and polypyrimidine tract-binding protein-associated splicing factor (PSF). In this study, we investigated expression of these transcription factors in mouse Y1 adrenal cells, a cell line that does not increase P450scc expression in response to IGF-I. Western blot analysis showed a greater expression of PSF in Y1 cells when compared with a mouse fibroblast cell line (NWTb3) in which IGF-I stimulates the P450scc IGFRE. The two cell lines expressed Sp1 equally, and IGF-I did not increase expression of either transcription factor. Chromatin immunoprecipitation analysis with Y1 chromatin confirmed that PSF and Sp1 bound to the IGFRE. When increasing amounts of Sp1 were expressed in Y1 cells, the IGFRE became responsive to IGF-I. Moreover, a mutant oligonucleotide IGFRE reporter construct that lacks PSF binding was responsive to IGF-I. In conclusion, Y1 adrenal cells are a physiological example of PSF repression of growth factor-stimulated (IGF-I) gene expression (P450scc). The dynamic nature of this repression is consistent with PSF functioning as a regulator of growth factor-stimulated gene expression in mammalian cells.

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The role of insulin-like growth factor 2 receptor-mediated homeobox gene expression in human placental apoptosis, and its implications in idiopathic fetal growth restriction

MHR Basic science of reproductive medicine ◽

10.1093/molehr/gaz047 ◽

2019 ◽

Vol 25 (9) ◽

pp. 572-585 ◽

Cited By ~ 1

Author(s):

Lynda K Harris ◽

Priyadarshini Pantham ◽

Hannah E J Yong ◽

Anita Pratt ◽

Anthony J Borg ◽

...

Keyword(s):

Gene Expression ◽

Transcription Factors ◽

Growth Factor ◽

Cell Growth ◽

Cell Line ◽

Gene Transcription ◽

Fetal Growth ◽

Fetal Growth Restriction ◽

Homeobox Gene ◽

Trophoblast Cell

Abstract Fetal growth restriction (FGR) is caused by poor placental development and function early in gestation. It is well known that placentas from women with FGR exhibit reduced cell growth, elevated levels of apoptosis and perturbed expression of the growth factors, cytokines and the homeobox gene family of transcription factors. Previous studies have reported that insulin-like growth factor-2 (IGF2) interacts with its receptor-2 (IGF2R) to regulate villous trophoblast survival and apoptosis. In this study, we hypothesized that human placental IGF2R-mediated homeobox gene expression is altered in FGR and contributes to abnormal trophoblast function. This study was designed to determine the association between IGF2R, homeobox gene expression and cell survival in pregnancies affected by FGR. Third trimester placentas were collected from FGR-affected pregnancies (n = 29) and gestation matched with control pregnancies (n = 30). Functional analyses were then performed in vitro using term placental explants (n = 4) and BeWo trophoblast cells. mRNA expression was determined by real-time PCR, while protein expression was examined by immunoblotting and immunohistochemistry. siRNA transfection was used to silence IGF2R expression in placental explants and the BeWo cell-line. cDNA arrays were used to screen for downstream targets of IGF2R, specifically homeobox gene transcription factors and apoptosis-related genes. Functional effects of silencing IGF2R were then verified by β-hCG ELISA, caspase activity assays and a real-time electrical cell-impedance assay for differentiation, apoptosis and cell growth potential, respectively. IGF2R expression was significantly decreased in placentas from pregnancies complicated by idiopathic FGR (P < 0.05 versus control). siRNA-mediated IGF2R knockdown in term placental explants and the trophoblast cell line BeWo resulted in altered expression of homeobox gene transcription factors, including increased expression of distal-less homeobox gene 5 (DLX5), and decreased expression of H2.0-Like Homeobox 1 (HLX) (P < 0.05 versus control). Knockdown of IGF2R transcription increased the expression and activity of caspase-6 and caspase-8 in placental explants, decreased BeWo proliferation and increased BeWo differentiation (all P < 0.05 compared to respective controls). This is the first study linking IGF2R placental expression with changes in the expression of homeobox genes that control cellular signalling pathways responsible for increased trophoblast cell apoptosis, which is a characteristic feature of FGR.

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Inhibition of cellular proliferation by the Wilms' tumor suppressor WT1 is associated with suppression of insulin-like growth factor I receptor gene expression.

Molecular and Cellular Biology ◽

10.1128/mcb.15.7.3516 ◽

1995 ◽

Vol 15 (7) ◽

pp. 3516-3522 ◽

Cited By ~ 76

Author(s):

H Werner ◽

Z Shen-Orr ◽

F J Rauscher ◽

J F Morris ◽

C T Roberts ◽

...

Keyword(s):

Gene Expression ◽

Growth Factor ◽

Tumor Suppressor ◽

Cell Line ◽

Cellular Proliferation ◽

Wilms Tumor ◽

Gene Promoter ◽

R Gene ◽

Factor I ◽

Igf I

We have investigated the regulation of the insulin-like growth factor I receptor (IGF-I-R) gene promoter by the Wilms' tumor suppressor WT1 in intact cells. The levels of endogenous IGF-I-R mRNA and the activity of IGF-I-R gene promoter fragments in luciferase reporter constructs were found to be significantly higher in G401 cells (a Wilms' tumor-derived cell line lacking detectable WT1 mRNA) than in 293 cells (a human embryonic kidney cell line which expresses significant levels of WT1 mRNA). To study whether WT1 could suppress the expression of the endogenous IGF-I-R gene, WT1-negative G401 cells were stably transfected with a WT1 expression vector. Expression of WT1 mRNA in G401 cells resulted in a significant decrease in the rate of cellular proliferation, which was associated with a reduction in the levels of IGF-I-R mRNA, promoter activity, and ligand binding and with a reduction in IGF-I-stimulated cellular proliferation, thymidine incorporation, and anchorage-independent growth. These data suggest that a major aspect of the action of the WT1 tumor suppressor is the repression of IGF-I-R gene expression.

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Regulation of insulin-like growth factor-I gene expression by growth factors in cultured vascular smooth muscle cells

Journal of Endocrinology ◽

10.1677/joe.0.1250381 ◽

1990 ◽

Vol 125 (3) ◽

pp. 381-386 ◽

Cited By ~ 50

Author(s):

K. E. Bornfeldt ◽

H. J. Arnqvist ◽

G. Norstedt

Keyword(s):

Gene Expression ◽

Smooth Muscle ◽

Growth Factor ◽

Smooth Muscle Cells ◽

Muscle Cells ◽

Basic Fgf ◽

Aortic Smooth Muscle ◽

Factor I ◽

Igf I ◽

I Gene

ABSTRACT The aim of this investigation was to study the regulation of insulin-like growth factor-I (IGF-I) gene expression in cultured rat aortic smooth muscle cells. Near-confluent cells were deprived of serum for 24 h and then exposed to IGF-I, insulin, serum, basic fibroblast growth factor (basic FGF), platelet-derived growth factor (PDGF-BB; consisting of B-chain homodimer) or GH for 24 h. Levels of IGF-I mRNA were measured by solution hybridization. The level of IGF-I mRNA was markedly decreased by 10% (v/v) newborn calf serum (78 ± 4 (s.e.m.) % decrease), 1 nmol basic FGF/1 (53 ± 8%), and 1 nmol PDGF-BB/1 (40 ± 3%) when measured after 24 h. The effect of PDGF-BB was significant after 6 h and became more marked after 24 h. GH (1 nmol/l or 0.1 μmol/l or insulin (1 nmol/l had no effect after 24 h, whereas IGF-I (1 nmol/l and insulin (10 μmol/l increased IGF-I mRNA 64 ± 20% and 46±14% respectively. The increase caused by IGF-I was demonstrated after 3 h, and was most marked after 24 h. Using Northern blot analysis of cultured aortic smooth muscle cells, IGF-I transcripts of 7-4, 1.7 and 1.1–0.8 kilobases were observed. Exposure of the cells to 10% serum, 1 nmol basic FGF/1 or 1 nmol PDGF-BB/1 for 48 h increased the cell number by 104 ±7%, 64 ± 3% and 61±22% respectively, while IGF-I, insulin and GH had little effect. In conclusion, IGF-I, and high concentrations of insulin, increased IGF-I mRNA in vascular smooth muscle cells, whereas factors which were stronger mitogens decreased IGF-I gene expression. Journal of Endocrinology (1990) 125, 381–386

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Insulin-like growth factor-I signaling is modified during chondrocyte differentiation

Journal of Endocrinology ◽

10.1677/joe.1.05873 ◽

2004 ◽

Vol 183 (3) ◽

pp. 477-486 ◽

Cited By ~ 56

Author(s):

Chanika Phornphutkul ◽

Ke-Ying Wu ◽

Xu Yang ◽

Qian Chen ◽

Philip A Gruppuso

Keyword(s):

Growth Factor ◽

Cell Line ◽

Chondrocyte Differentiation ◽

Erk Pathway ◽

Insulin Like Growth Factor ◽

Erk Activation ◽

Atdc5 Cell ◽

Factor I ◽

Proliferation And Differentiation ◽

Igf I

Insulin-like growth factor-I (IGF-I) is a critical regulator of skeletal growth. While IGF-I has been shown to be a potent chondrocyte mitogen in vitro, its role in chondrocyte differentiation is less well characterized. We chose to study the action of IGF-I on an accepted model of chondrocyte differentiation, the ATDC5 cell line. Insulin concentrations sufficiently high to interact with the IGF-I receptor are routinely used to induce ATDC5 cells to differentiate. Therefore, we first examined the ability of IGF-I to promote chondrocyte differentiation at physiological concentrations. IGF-I could induce differentiation of these cells at concentrations below 10 nM. However, increasing IGF-I concentrations were less potent at inducing differentiation. We hypothesized that mitogenic effects of IGF-I might inhibit its differentiating effects. Indeed, the extracellular-signal-regulated kinase (ERK)-pathway inhibitor PD98059 inhibited ATDC5 cell DNA synthesis while enhancing differentiation. This suggested that the ability of IGF-I to promote both proliferation and differentiation might require that its signaling be modulated through the differentiation process. We therefore compared IGF-I-mediated ERK activation in proliferating and hypertrophic chondrocytes. IGF-I potently induced ERK activation in proliferating cells, but minimal ERK response was seen in hypertrophic cells. In contrast, IGF-I-mediated Akt activation was unchanged by differentiation, indicating intact upstream IGF-I receptor signaling. Similar findings were observed in the RCJ3.1C5.18 chondrogenic cell line and in primary chick chondrocytes. We conclude that IGF-I promotes both proliferation and differentiation of chondrocytes and that the differentiation effects of IGF-I may require uncoupling of signaling to the ERK pathway.

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Effect of exogenous chicken growth hormone (cGH) administration on insulin-like growth factor-I (IGF-I) gene expression in domestic fowl

Molecular and Cellular Endocrinology ◽

10.1016/0303-7207(95)96796-k ◽

1995 ◽

Vol 114 (1-2) ◽

pp. 157-166 ◽

Cited By ~ 29

Author(s):

G Rosselot

Keyword(s):

Gene Expression ◽

Growth Hormone ◽

Growth Factor ◽

Domestic Fowl ◽

Insulin Like Growth Factor ◽

Factor I ◽

Igf I ◽

Growth Factor I ◽

I Gene

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Integrated Genomic and Proteomic Analyses of Gene Expression in Mammalian Cells

Molecular & Cellular Proteomics ◽

10.1074/mcp.m400055-mcp200 ◽

2004 ◽

Vol 3 (10) ◽

pp. 960-969 ◽

Cited By ~ 507

Author(s):

Qiang Tian ◽

Serguei B. Stepaniants ◽

Mao Mao ◽

Lee Weng ◽

Megan C. Feetham ◽

...

Keyword(s):

Gene Expression ◽

Mammalian Cells ◽

Proteomic Analyses ◽

Expression In Mammalian Cells

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Gene expression in skeletal muscle

Biochemical Society Transactions ◽

10.1042/bst0300285 ◽

2002 ◽

Vol 30 (2) ◽

pp. 285-290 ◽

Cited By ~ 55

Author(s):

G. Goldspink

Keyword(s):

Gene Expression ◽

Growth Factor ◽

Molecular Motors ◽

Mechanical Activity ◽

Reading Frame ◽

Metabolic Genes ◽

Igf I ◽

Systemic Factors ◽

Repair Factor ◽

Qualitative Changes

Muscle has an intrinsic ability to change its mass and phenotype in response to activity. This process involves quantitative and qualitative changes in gene expression, including that of the myosin heavy chain isogenes that encode different types of molecular motors. This, and the differential expression of metabolic genes, results in altered fatigue resistance and power output. The regulation of muscle mass involves autocrine as well as systemic factors. We have cloned the cDNAs of local and systemic isoforms of insulin-like growth factor-I (IGF-I) from exercised muscle. Although different isoforms are derived from the IGF-I gene by alternative splicing, the RNA transcript of one of them is only detectable following injury and/or mechanical activity. Thus this protein has been called mechano growth factor (MGF). Because of a reading-frame shift, MGF has a different 3′ sequence and a different mode of action compared with systemic or liver IGF-I. Although MGF has been called a growth factor, it may be regulated as a local repair factor.

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