bluuebunny/crossref_metadata_2025_split huggingface dataset:
Distribution of globin genes and histone variants in micrococcal nuclease‐generated subfractions of chromatin from Friend erythroleukemia cells at different malignant states
Authors: Leonardson Kathleen E. , Levy Stuart B. 
Published: May 2005

AbstractThe distribution of the α and β‐globin genes and histone variants was examined in micrococcal nuclease‐generated chromatin fractions of three Friend murine erythroleukemia cell types differing in malignant potential and inducibility to erythroid differentiation. A preferential concentration of globin gene sequences, as compared to satellite DNA, was noted in a physiological salt‐soluble, histone H1‐depleted, mononucleosomal chromatin fraction (Sup 120) in all Friend cell types, even those in which the globin gene was not capable of transcriptional activation by chemical induction. The level of globin gene enrichment in the Sup 120 fraction was highest in the most malignant and inducible cell type. The chemical induction of erythroid differentiation in this cell line did not change the distribution of globin genes in the chromatin fractions. The Sup 120 chromatin fraction prepared from mouse brain nuclei was not enriched in globin genes. Besides the previously reported low H2A.1/H2A.2 ratio [Blankstein and Levy: Nature 260:638–640, 1976], chromatin from the most tumorigenic cell type showed the lowest H2B.2 to H2B.1 ratio, highest levels of histone H4 acetylation, and the most pronounced change in relative amounts of two major electrophoretic bands of histone H1 variants as compared to the less malignant cell types. The histone variant content of the micrococcal nuclease‐generated chromatin fractions from the three Friend cell types reflected the core histone variant differences for the respective intact nuclei. However, the electrophoretic separation of mononucleosomes by size revealed several classes with different H2A variant ratios. The results demonstrate the existence of structural differences in globin gene and histone variants in erythroleukemia cell chromatin associated with distinguishable phenotypes during malignant cell progression.
Protected regions in the chicken α2(1) procollagen promoter in differentiated tissues
Authors: Truter Sharada L. , Parker M. Iqbal 
Published: May 2005

AbstractThe higher ordered structure of the chicken α2(I) procollagen gene was analyzed in chromatin isolated from expressing (lung) and nonexpressing (reticulocyte and erythrocyte) tissues. Digestion of DNA with methylation sensitive restriction endonucleases revealed that this gene was methylated in all tissues examined and that no differences existed in the promoter methylation patterns between expressing and nonexpressing tissues. DNAse 1 hypersensitive sites were located between 100–300 bp upstream from the transcription initiation site and within the first intron. These sites were also hypersensitive to the single‐strand specific S1 nuclease, implying that this region of the gene in the chromatin is either in an unfolded single‐stranded conformation or under severe conformational stress. These differences in the α2(1) chromatin structure were confirmed by the finding that the promoter was more accessible to restriction endonuclease digestion in the expressing tissues than in the nonexpressing tissues. Digestion of chromatin with Pst I and Sma I revealed that some of these sites in the promoter were differentially protected by DNA‐binding proteins in the two tissue types. These protected sites were located as far upstream as −1,600 and downstream within the first intron at +800.
Differential partition of anticoagulant heparan sulfate proteoglycans synthesized by endothelial and fibroblastic cell lines
Authors: de Agostini Ariane I. , Ramus Marie‐Andrée , Rosenberg Robert D. 
Published: May 2005

AbstractThe heparan sulfate proteoglycans that bind and activate antithrombin III (aHSPGs) are synthesized by endothelial cells as well as other nonvascular cells. We determined the amounts of cell surface–associated and soluble aHSPGs generated by the rat fat pad endothelial (RFP) cell line and the fibroblast (LTA) cell line. The RFP cells exhibit higher levels of cell surface–associated aHSPGs as compared to LTA cells, whereas LTA cells release larger amounts of soluble aHSPGs as compared to RFP cells. After confluence RFP cells show an increase in both cell surface–associated and soluble aHSPGs. In contrast, postconfluent LTA cells maintain a constant level of cell surface–associated and soluble aHSPGs. These observations indicate that different cells types can preferentially accumulate aHSPGs as cell surface–associated or soluble forms which could reflect alternate biological functions.
Inhibitors of tyrosine and ser/thr phosphatases modulate the heat shock response
Authors: Mivechi Nahid F. , Murai Toshimi , Hahn George M. 
Published: May 2005

AbstractFollowing heat shock the expression of heat shock genes is regulated by the heat shock transcription factor, HSF, known to bind to arrays of the heat shock element, NGAAN, upstream of the heat shock genes. Phosphorylation of HSF is necessary for its activation. We report that the treatment of Chinese hamster HA‐1 cells with 250 nM of okadaic acid (OA), a ser/thr phosphatase inhibitor, leads to an increase in activated HSF after heat shock. This is followed by the activation of the transcription of heat shock genes as assayed by the increase in the synthesis of β‐galactosidase in an HA‐1 cell line containing the heat shock promoter ligated to the β‐galactosidase gene. To investigate the specificity of OA, we used other phosphatase inhibitors. We found that treatment of HA‐1 cells with 500 μM of sodium vanadate, an inhibitor of tyr/phosphatases, resulted in a three to fivefold reduction in HSF activation and binding to the heat shock element following heat shock. Such reduction in HSF activation virtually abolished β‐galactosidase induction. Reduced HSP synthesis was further confirmed by SDS‐PAGE and Western blot analysis using anti–HSP‐70 and 28 antibodies. Sodium vanadate treatment of heat shocked cells greatly reduced levels of thermotolerance. These results show that ser/thr and specifically tyr/phosphatase inhibitors modulate the signal transduction pathway of HSF activation.
2,3,7,8‐Tetrachlorodibenzo‐p‐dioxin inhibits differentiation of normal diploid rat osteoblasts in vitro
Authors: Gierthy John F. , Silkworth J. B. , Tassinari Melissa , Stein Gary S. , Lian Jane B. 
Published: May 2005

AbstractThe influence of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD), a potent halogenated aromatic hydrocarbon, on the development of bone tissue‐like organization in primary cultures of normal diploid calvarial‐derived rat osteoblasts was examined. Initially, when placed in culture, these cells actively proliferate while expressing genes associated with biosynthesis of the bone extracellular matrix. Then, post‐proliferatively, genes are expressed that render the osteoblast competent for extracellular matrix mineralization and maintenance of structural as well as functional properties of the mature bone‐cell phenotype. Our results indicate that, in the presence of TCDD, proliferation of osteoblasts was not inhibited but post‐confluent formation of multicellular nodules that develop bone tissue‐like organization was dramatically suppressed. Consistent with TCDD‐mediated abrogation of bone nodule formation, expression of alkaline phosphatase and osteocalcin was not upregulated post‐proliferatively. These findings are discussed within the context of TCDD effects on estrogens and vitamin D‐responsive developmental gene expression during osteoblast differentiation and, from a broader biological perspective, on steroid hormone control of differentiation.
Localization of erythropoietin mRNA in the rat kidney by polymerase chain reaction
Authors: da Silva Jean‐Louis , Schwartzman Michal L. , Goodman Alvin , Levere Richard D. , Abraham Nader G. 
Published: May 2005

AbstractErythropoietin (Epo) is a glycoprotein secreted by kidney cells which plays an important role in the regulation of erythropoiesis. Localization of the Epo production by immunohistochemical studies and in situ hybridization has not been definitively established and is still a matter of controversy. Epo and glyceraldehyde 3‐dehydrogenase (GAPDH) mRNA levels were determined in total RNA isolated from control and CoCl2‐treated rats using a coupled reverse transcriptase/polymerase chain reaction method (RT/PCR). As indicated by the amount of amplification product, Epo mRNA levels were several‐fold higher in CoCl2‐treated rat kidney. In contrast, GAPDH mRNA levels were similar in control and CoCl2‐treated rats. This RT/PCR method was also used to assess the level of Epo and GAPDH mRNA in microdissected nephron segments. All nephron segments tested lacked any detectable levels of Epo mRNA in either control or CoCl2‐treated rats. On the other hand, peritubular cells (capillary fraction: afferent/efferent arteriole, vasa recta) were the only cells where the Epo mRNA was detected. Using a specific primer for GAPDH, the RT/PCR method could identify GAPDH mRNA in all microdissected nephron segments where the Epo mRNA was not expressed. Thus, a combination of microdissected nephron segments and RT/PCR enabled us to detect GAPDH mRNA populations in all nephron segments, whereas the failure to detect Epo mRNA in all segments but the capillary fraction, is due to the specific and localized expression of the Epo gene to this fraction.
Guanine nucleotide binding regulatory proteins in liver from obese humans with and without type II diabetes: Evidence for altered “cross‐talk” between the insulin receptor and Gi‐proteins
Authors: Caro José F. , Raju Madhu S. , Caro Maricelina , Lynch Christopher J. , Poulos John , Exton John H. , Thakkar Jay K. 
Published: May 2005

AbstractA novel pathway for physiological “cross‐talk” between the insulin receptor and the regulatory Gi‐protein has been demonstrated. We tested the hypothesis that a coupling defect between Gi and the insulin receptor is present in the liver of obese patients with and without type li diabetes. Insulin 1 × 10−9 M (∼ ED50) and 1 × 10−7 M (Max) inhibited pertussis toxin‐catalyzed ADP ribosylation of Gi in human liver plasma membranes from lean and obese nondiabetic patients. However, 1 × 10−7 M insulin was without effect in membranes from patients with type II diabetes. This coupling defect was not intrinsic to Gi, since Mg2+ and GTPγS inhibited pertussis toxin‐catalyzed ADP ribosylation in both diabetic and nondiabetic patients. Binding of insulin of the α‐subunit and activation of the tyrosine kinase intrinsic to the β‐subunit of the insulin receptor are not responsible for the coupling defect. 125I insulin binding is the same in obese patients with or without diabetes. Tyrosine kinase of the insulin receptor is decreased in diabetes. However, a monoclonal antibody to the insulin receptor (MA‐20) at equimolar concentrations with insulin equally inhibits pertussis toxin‐catalyzed ADP ribosylation of Gi without activating tyrosine kinase or insulin receptor autophosphorylation. Immunodetection of G‐proteins suggested that Gi3α was normal in diabetes and Gi1‐2α was decreased by 40% in the diabetic group as compared to the obese nondiabetic group but was normal when compared to the lean non diabetic group. We conclude that the novel pathway of insulin signaling involving the regulatory Gi proteins via biochemical mechanisms not directly involving the tyrosine kinase of the insulin receptor is altered in obese type II diabetes and offers a new target for the search of the mechanism(s) of insulin resistance.
Absence of transforming growth factor‐β responsiveness in the tamoxifen growth‐inhibited human breast cancer cell line CAMA‐1
Authors: Ji Hongjun , Stout Laurence E. , Zhang Qingqing , Zhang Ruoping , Leung Helen T. , Leung Benjamin S. 
Published: May 2005

AbstractTamoxifen has been an effective antiestrogen in suppressing breast cancer growth which is estrogen‐responsive or dependent. Early studies have provided circumstantial evidence that transforming growth factor‐β (TGF‐β) may be an autocrine mediator of tamoxifen action. Therefore, it is both fundamentally important and clinically relevant to investigate the relationship between tamoxifen and TGF‐β. In this study, we demonstrated that CAMA‐1 cells, which are sensitive to tamoxifen inhibition, did not respond to TGF‐β growth inhibition. The type I and II TGF‐β receptors were undetectable by the radio‐ligand affinity labeling technique. Despite the presence of a normal TGF‐β type II receptor gene, the mRNA transcript of the gene was undetectable by the extremely sensitive Intron‐differential RNA/PCR method. The possibility that the lack of TGF‐β receptors might be intimately linked to the absence of normal retinoblastoma (Rb) gene products, as suggested by previous studies of retinoblastoma cells, was further investigated. The lack of TGF‐β receptor expression was found due to reasons other than the absence, deletion or abnormality of the Rb gene because a normal Rb gene and its hyper‐ and hypo‐phosphorylated protein products were detected in CAMA‐1 cells. In conclusion, our results suggest that the TGF‐β system is not obligatory for antiestrogen growth inhibition of CAMA‐1 cells.
Marrow stromal cell commitment to mineralization under the effect of a prolyl hydroxylase inhibitor
Authors: Klein Benjamin Y. , Gal Irena , Segal David 
Published: May 2005

AbstractMitochondrial response to the effect of a hydroxylase (PH) inhibitor was tested in marrow stromal cells during stimulation of osteoprogenitor cell (OPC) differentiation. The rationale for this was to explore pathways of regulatory interactions between procollagen synthesis and mitochondrial respiration that could be linked to the commitment of OPCs to mineralization. Stimulated OPCs exposed to the PH inhibitor cis‐hydroxyproline (cis‐HP), compared to the noninhibiting isomer trans‐HP, for 11 days showed a dose‐dependent decrease in cell proliferation, the surviving cells showed increased alkaline phosphatase activity. Trans‐HP did not influence the cis‐HP effect on ALP and on proliferation arrest. Short time exposures, 2–3 days, to cis‐HP at different periods suggested that Days 0–3 and 3–5 were critical for the commitment to Day 21 mineralization of OPCs. On Days 0–3 cells were most sensitive to cis‐HP, since on Day 11, 8 days after removal of cis‐HP, they were too scarce to be counted by the staining method. However, the presence of 5.0 mM cis‐HP in the cultures during Days 3–5 has induced on Day 21 close to 24‐fold more mineralization/cell than controls, compared to the trans‐HP effect, which was only close to 3‐fold. The presence of cis‐HP in the cultures on Days 0–3 has augmented the mitochondrial Day 3 retention of rhodamine 123 (Rho) in the stromal cells, relative to controls, compared to the presence of trans‐HP. However, the presence of cis‐HP during Days 3–5 or 3–6 resulted in lower Day 5 Rho retention, relative to controls, which was not significantly different from the retention that resulted from trans‐HP. Since Rho retention is related to the final result of aerobic respiration level, these results are interpreted as a cis‐HP inhibitory effect on procollagen peptidyl‐proline hydroxylation, which may in turn release oxygen surpluses, to be available for mitochondrial consumption. The fall in Rho retention responses to cis‐HP between Days 0–3 and 3–5 is suggesting either abrupt decrease in proline hydroxylation or poor mitochondrial sensitivity to oxygen in Day 3–5 cultures.
Multiple molecular levels of cell cycle regulation
Authors: Pardee A. B. 
Published: May 2005

AbstractThe objective of this brief review is to stress the importance of multiple levels of molecular regulation of complex processes such as cell growth and to illustrate their derangements as they occur in cancer cells. One major research emphasis today is the regulation of transcription by binding of transactivating proteins to promoter motifs. Another focus is on the multiple roles of protein phosphorylations in signal transduction pathways. Evidence is strong, however, that major controls exist at numerous other molecular levels as well (Fig. 1). These include pre‐mRNA processing, pre‐mRNA degradation, mRNA degradation, control of translation, permanent protein modifications, protein degradation, reversible covalent protein alterations, noncovalent interactions with small molecules and with other proteins, and effects of relocations into cell compartments. These controls are exhibited in all biological processes. A few illustrative examples are briefly discussed, which come mainly from our researches in the area of cell cycle regulation and its derangement in cancer.
Uncoordinate regulation of collagenase, stromelysin, and tissue inhibitor of metalloproteinases genes by prostaglandin E2: Selective enhancement of collagenase gene expression in human dermal fibroblasts in culture
Authors: Mauviel Alain , Halcin Cynthia , Vasiloudes Panayiotis , Parks William C. , Kurkinen Markku , Uitto Jouni 
Published: May 2005

AbstractThe degradative effects of interleukin‐1 (IL‐1) on the extracellular matrix of connective tissue are mediated primarily by metalloproteinases and prostaglandins. Clinical observations suggest that these effects can be prevented, to some extent, by the use of non‐steroidal anti‐inflammatory drugs. We have examined the role of prostaglandin E2 (PGE2) in IL‐1‐induced gene expression by human skin fibroblasts in culture. Incubation of confluent fibroblast cultures with varying concentrations (0.01–1.0 μg/ml) of PGE2 led to a dose‐dependent elevation of collagenase mRNA steady‐state levels, the promoter activity, and the secretion of the protein, whereas relatively little effect was observed on stromelysin and TIMP gene expression. Exogenous PGE2 had no additive or synergistic effect with IL‐1 on collagenase gene expression. Furthermore, commonly used non‐steroidal anti‐inflammatory drugs (indomethacin, acetyl salicylic acid and ibuprofen), at doses which block prostaglandin synthesis in cultured fibroblasts, failed to counteract IL‐1‐induced collagenase and stromelysin gene expression, nor did they affect TIMP expression. Although the effects of PGE2 did not potentiate those of IL‐1 on collagenase gene expression in vitro, one could speculate that massive production of PGE2 by connective tissue cells in vivo in response to inflammatory mediators such as IL‐1 or tumor necrosis factor‐α, could lead to sustained expression of collagenase in connective tissue cells after clearance of the growth factors.
Subnuclear distribution of the vitamin D receptor
Authors: Bidwell Joseph P. , van Wijnen André J. , Fey Edward G. , Merriman Harold , Penman Sheldon , Stein Janet L. , Stein Gary S. , Lian Jane B. 
Published: May 2005

AbstractThe subnuclear distribution of the vitamin D receptor was investigated to begin addressing the contribution of nuclear architecture to vitamin D–responsive control of gene expression in ROS 17/2.8 rat osteosarcoma cells. The nuclear matrix is an anastomosing network of filaments that is functionally associated with DNA replication, transcription, and RNA processing. The representation of vitamin D receptor in the nuclear matrix and nonmatrix nuclear fractions was determined by the combined application of (1) sequence‐specific interactions with the vitamin D receptor binding element of the rat bone‐specific osteocalcin gene promoter and (2) Western blot analysis. Both methods confirmed the presence of vitamin D receptor in the nonmatrix nuclear fraction and the absence of detectable vitamin D receptors associated with the nuclear matrix. In contrast, these same nuclear matrix proteins preparations exhibited association with the general transcription factor AP‐1 and a bone tissue‐specific promoter binding factor NMP2. NMP‐2 exhibits recognition for a promoter domain contiguous to the vitamin D‐responsive element of the osteocalcin gene, although the vitamin D receptor does not appear to be a component of the nuclear matrix proteins. Interrelationships between nuclear matrix proteins and nonmatrix nuclear proteins, in mediating steroid hormone responsiveness of a vitamin D–regulated promoter, are therefore suggested.
Putative nuclear localization signals (NLS) in protein transcription factors
Authors: Boulikas Teni 
Published: May 2005

AbstractWe have recognized about ten distinct forms of strongly basic hexapeptides, containing at least four arginines and lysines, characteristic of nuclear proteins among all eukaryotic species, including yeast, plants, flies and mammals. These basic hexapeptides are considered to be different versions of a core nuclear localization signal, NLS. Core NLSs are present in nearly all nuclear proteins and absent from nearly all “nonassociated” cytoplasmic proteins that have been investigated. We suggest that the few (∼ 10%) protein factors lacking a typical NLS core peptide may enter the nucleus via their strong crosscomplexation with their protein factor partners that possess a core NLS. Those cytoplasmic proteins found to possess a NLS‐like peptide are either tightly associated with cell membrane proteins or are integral components of large cytoplasmic protein complexes. On the other hand, some versions of core NLSs are found in many cell membrane proteins and secreted proteins. It is hypothesized that in these cases the N‐terminal hydrophobic signal peptide of extracellular proteins and the internal hydrophobic domains of transmembrane proteins are stronger determinants for their subcellular localization. The position of core NLSs among homologous nuclear proteins may or may not be conserved; however, if lost from an homolgous site it appears elsewhere in the protein.This search provides a set of rules to our understanding of the nature of core nuclear localization signals: (1) Core NLS are proposed to consist most frequently of an hexapeptide with 4 arginines and lysines; (2) aspartic and glutamic acid residues as well as bulky amino acids (F, Y, W) need not to be present in this hexapeptide; (3) acidic residues and proline or glycine that break the α‐helix are frequently in the flanking region of this hexapeptide stretch; (4) hydrophobic residues ought not to be present in the core NLS flanking region allowing for the NLS to be exposed on the protein. In this study we attempt to classify putative core NLS from a wealth of nuclear protein transcription factors from diverse species into several categories, and we propose additional core NLS structures yet to be experimentally verified. © 1994 Wiley‐Liss, Inc.
Towards and understanding of nuclear morphogenesis
Authors: Georgatos Spyros D. 
Published: May 2005

AbstractIn the age of “virtual reality,” the imperfect microscopic silhouettes of cells and organelles are gradually being replaced by calligraphic computer drawings. In this context, textbooks and introductory slides often depict the cell nucleus as a smooth‐shaped, featureless object. However, in reality, the nuclei of different cells possess distinct sizes and morphological features which develop in a programmed fashion as each cell differentiates. To dissect this complex morphogenetic process, we need to identify the basic elements that determine nuclear architecture and the regulatory factors involved. Recently, clues about the identity of these components have been obtained both by systematic analysis and by serendipity. This review summarizes a few recent findings and ideas that may serve as a first forum for future discussions and, I hope, for further work on this topic. © 1994 Wiley‐Liss, Inc.