1,721,072 research outputs found
Expression of cell-cycle-dependent genes in phytohemagglutinin-stimulated human lymphocytes.
No full textWe have investigated the expression of certain cell-cycle-dependent genes in human peripheral blood mononuclear cells (PBMC) stimulated by phytohemagglutinin (PHA). The genes studied had been previously identified as cell-cycle dependent in other cell types from different species and were induced by different mitogens. One of these genes (2F1) and the gene for the interleukin 2 receptor were induced by PHA even in cultures partially depleted of accessory cells where the lymphocytes grew in size but failed to enter S phase. The other genes (c-myc, 4F1, JE-3, and KC-1) were induced only in complete cultures of PBMC stimulated by PHA. These results confirm the dissociation between growth in size and cell DNA replication that can occur during cell-cycle progression. Moreover, the time course of appearance of detectable levels of RNA for these genes suggests that they may be used as markers of cell-cycle progression in the transition of lymphocytes from G0 to S phase
Effect of interleukin-2 on the expression of cell cycle genes in human T lymphocytes.
No full textWe have studied the expression of seven cell cycle-dependent genes in phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells, in macrophage-depleted cultures and in macrophage-depleted cultures plus Interleukin-2 (IL-2). The expression of all seven genes is increased in PHA stimulated peripheral cells. Only two (2F1 and the IL-2 receptor) are increased in PHA-stimulated macrophage depleted cultures. Addition of IL-2 to these cultures increased the RNA levels of four genes (KC-1, c-myc, beta-actin and IL-2R), but has no effect on three others (4F1, 2F1, and JE-3). The results indicate that the expression of these cell cycle genes is regulated by different components of the mitogenic stimulus
Human gene for proliferating cell nuclear antigen has pseudogenes and localizes to chromosome 20.
No full textWe have isolated from a human genomic library a pseudogene of the proliferating cell nuclear antigen (PCNA) gene. Its sequence shows a 78% similarity with the human PCNA/cDNA. The PCNA gene is located on human chromosome 20, while the pseudogene maps to chromosome region Xpter in equilibrium Xq13. An additional locus detected by the full-length PCNA cDNA, but not by intron probes, segregates concordantly with chromosome region 6p12 in equilibrium 6pter and probably represents a second pseudogene
An antibody that specifically recognizes a phosphorylated IGF-IR
No full textThe IGF-I receptor (IGF-IR) plays an important role in cell growth control, in malignant transformation, and in cell survival. Its role in human cancer has been firmerly established. High level of IGF-IR in breast cancer is highly correlated with ipsilateral breast tumor recurrence following lumpectomy and radiation therapy. IGF-IR signaling occurs upon activation by its ligands, that induce autophosphorylation of the receptor at several tyrosine residues.. Phosphorylation of tyrosine residue at position 1316 (Y1316) is necessary for tumor formation in nude mice, although not essential for IGF-I-induced mitogenesis.
We generated a rabbit polyclonal antibody that specifically recognizes a phosphorylated IGF-IR. This antibody (anti-pY1316/IGF-IR) do not crossreact with a phosphorylated Insulin receptor, and do not recognizes a C-terminus-truncated IGF-IR nor a mutant IGF-IR having the Y1316 replaced with phenylalanine (Y1316F).
The anti-pY1316/IGF-IR antibody can be used in immunohistchemistry and can be applied for the detection of activated IGF-IRs in human tumor sections. Analyses of Y1316-IGF-IR phosphorylation level are in progress to establish whether this parameter may have a prognostic value in human breast cancer
Inhibition of cellular proliferation by antisense oligodeoxynucleotides to PCNA cyclin.
No full textThe proliferating cell nuclear antigen (PCNA or cyclin) is a nuclear protein recently identified as a cofactor of DNA polymerase delta. When exponentially growing Balb/c3T3 cells are exposed to antisense oligodeoxynucleotides to PCNA, both DNA synthesis and mitosis are completely suppressed. A corresponding sense oligodeoxynucleotide has no inhibitory effects. These experiments indicate that PCNA (cyclin) is important in cellular DNA synthesis and in cell cycle progressio
The IGF-I receptor in cell growth, transformation and apoptosis
No full textThe following brief summary is based on a recent
review by Rubin and Baserga w1x, and the reader is
referred to that review for extended references. A
simplified representation of the IGF system includes
3 receptors, 3 ligands and 6 IGF binding proteins
.IGFBPs.. The ligands are the mature IGF-I.70
aminoacids., the mature IGF-II.67 aminoacids. and
insulin. The receptors are the type I insulin-like
growth factor receptor.IGF-IR., the insulin receptor
.IR. and the IGF-II receptor .IGF-IIR.. In terms of
cellular proliferation, the IGF-IR is the most active of
the 3 receptors.see below.: it is activated by all 3
ligands, and, although it has several functional features
in common with the IR w2x, the b subunit of the
IGF-IR is 10 times more mitogenic than the beta
subunit of the IR w3x. Insulin at supraphysiological
concentrations also activates the IGF-IR; this is an
important point to remember, because when insulin is
used at mg concentrations, it exerts its mitogenic
stimulation through the IGF-IR w4x. Under appropriate
conditions, the IR is mitogenic
The IGF-I receptor in mitogenesis and transformation of mouse embryo cells: role of receptor number
No full textThe type 1 receptor for insulin-like growth factors (IGF-IR) plays an important role in the growth and transformation of several types of cells. We have investigated the role of IGF-IR number in IGF-I-mediated mitogenesis and transformation of mouse embryo fibroblasts. We have used R- cells (3T3-like cells originating from mouse embryos with a targeted disruption of the IGF-IR genes) transfected with a plasmid expressing the human IGF-IR cDNA to generate clones with receptor numbers ranging from zero to 10(6) receptors per cell. In this model, between 15,000 and 22,000 receptors per cell are sufficient to render mouse embryo cells competent to grow in serum-free medium supplemented solely with IGF-I. For growth in soft agar, 30,000 receptors per cell seem to be the minimum requirement. These experiments indicate that a small increment in the number of receptors per cell, well within the physiological range, can modulate the mitogenic and transforming activities of the IGF-IR in 3T3-like cells
Downregulation of the upstream binding factor1 by glycogen synthase kinase3beta in myeloid cells induced to differentiate.
No full textThe upstream binding factor 1 (UBF1), one of the proteins that regulate the activity of RNA polymerase I, is downregulated in 32D myeloid cells induced to differentiate into granulocytes, either by the type 1 insulin-like growth factor (IGF-1) or the granulocytic colony stimulating factor (G-CSF). Downregulation of UBF1 is largely due to protein degradation, while mRNA levels are not affected. Inhibition of UBF1 degradation by lithium chloride (LiCl)and lactacystin suggest a role of glycogen synthase kinase beta (GSK3beta) in a proteasome-dependent degradation of UBF. GSK3beta phosphorylates in vitro and in vivo the UBF protein, which has five putative motifs for phosphorylation by GSK3beta. Elimination and/or mutations of these motifs stabilize the UBF1 protein even in cells induced to differentiate. Conversely, a stably transfected, constitutively active GSK3beta accelerates the downregulation of UBF1. We show further that activation of the differentiating protein C/EPBalpha in 32D cells transformed by the oncogenic BCR/ABL protein causes downregulation of UBF1. Finally, inhibition of differentiation of myeloid cells by a dominant negative mutant of Stat3 stabilizes the UBF1 protein, while rapamycin-induced differentiation of myeloid cells downregulates UBF1 levels. Taken together, our results indicate that the induction of granulocytic differentiation in 32D murine myeloid cells causes the degradation of UBF1, via GSK3beta and the proteasome pathway. c 2006 Wiley-Liss, In
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