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  • 1990-1994  (3)
  • histone  (2)
  • ROS 17/2.8  (1)
  • 1
    ISSN: 0730-2312
    Keywords: intracellular Ca2+ ; 1β25-(OH)2D3 ; ROS 17/2.8 ; OC mRNA ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We have previously shown that one of the rapid nongenomic actions of 1α,25-dihydroxyvitamin D3 (1α,25-(OH)2D3), the increase in intracellular calcium (Ca2+), accompanies the increased osteocalcin (OC) mRNA steady-state levels in rat osteosarcoma cells. To determine the functional significance of the nongenomic actions, we have measured changes in intracellular Ca2+ as an indicator of the rapid effects and have assessed the effect of inhibition of the rapid increase in cellular Ca2+ by the inactive epimer, 1β,25-dihydroxyvitamin D3 (1β,25-(OH)2D3) on OC mRNA steady-state levels and transcription. 1β,25-dihydroxyvitamin D3 inhibited 1α,25-(OH)2D3 induced increases in intracellular Ca2+ and OC mRNA transcription at 1 hr and OC mRNA steady state levels at 3 hr. 1β,25-Dihydroxyvitamin D3 did not alter the binding of the vitamin D receptor complex to the vitamin D responsive element of the OC gene. The results demonstrate the functional importance of the rapid, nongenomic actions of 1α,25-(OH)2D3 in the genomic activation of the OC gene by the hormone in rat osteoblast-like cells, perhaps by modifying subtle structural and/or functional properties of the vitamin D-receptor DNA complex or by affecting other protein DNA interactions that support OC gene transcription. © 1992 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 47 (1991), S. 184-196 
    ISSN: 0730-2312
    Keywords: glucocorticoid ; transcription ; mRNA stability ; histone ; differentiation ; bone development ; osteoblast ; promoter factors ; collagen ; osteosarcoma cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The influence of dexamethasone on expression of the osteocalcin gene which encodes the most abundant non-collagenous and only reported bone-specific protein was examined in ROS 17/2.8 osteosarcoma cells which express a broad spectrum of genes related to bone formation. Consistent with previous reports, quantitation of cellular osteocalcin mRNA levels by Northern blot analysis, osteocalcin gene transcription by activity of the osteocalcin gene promoter fused to a chloramphenicol acetyl-transferase (CAT) mRNA coding sequence following transfection into ROS 17/2.8 cells, and osteocalcin biosynthesis by radioimmunoassay indicate that dexamethasone in a concentration range of 10-6 to 10-9 M only modestly modifies basal levels of osteocalcin gene expression. However, dexamethasone significantly inhibits these parameters of the vitamin D-induced upregulation of osteocalcin gene expression in both proliferating and in confluent ROS 17/2.8 cells. In this study, we observed that the extent to which abrogation of the vitamin D response occurs is dependent on basal levels of osteocalcin gene expression as reflected by a complete inhibition of the vitamin D-induced upregulation in a ROS 17/2.8K subline with low basal expression and only a partial reduction of the vitamin D stimulation in a ROS 17/2.8C subline with eightfold higher levels of basal expression. This effect of glucocorticoid appears to be at the transcriptional and post-transcriptional levels as demonstrated by a parallel decline in the cellular representation of osteocalcin mRNA, osteocalcin gene promoter activity, and osteocalcin biosynthesis. The complexity of the glucocorticoid effect on vitamin D-mediated transcriptional properties of the osteocalcin gene is indicated by persistence of sequence-specific protein-DNA interactions at two principal osteocalcin gene promoter regulatory elements, the osteocalcin (CCAAT) box which modulates basal level of transcription, and the vitamin D responsive element, where vitamin D-mediated enhancement of osteocalcin gene transcription is controlled.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0730-2312
    Keywords: phosphorylation ; cell cycle ; proliferation ; transcription ; histone ; development ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Cell cycle regulated gene expression was studied by analyzing protein/DNA interactions occurring at the H4-Site II transcriptional element of H4 histone genes using several approaches. We show that this key proximal promoter element interacts with at least three distinct sequence-specific DNA binding activities, designated HiNF-D, HiNF-M, and HiNF-P. HiNF-D binds to an extended series of nucleotides, whereas HiNF-M and HiNF-P recognize sequences internal to the HiNF-D binding domain. Gel retardation assays show that HiNF-D and HiNF-M each are represented by two distinct protein/DNA complexes involving the same DNA binding activity. These results suggest that these factors are subject to post-translational modifications. Dephosphorylation experiments in vitro suggest that both electrophoretic mobility and DNA binding activities of HiNF-D and HiNF-M are sensitive to phosphatase activity. We deduce that these factors may require a basal level of phosphorylation for sequence specific binding to H4-Site II and may represent phosphoproteins occurring in putative hyper- and hypo-phosphorylated forms. Based on dramatic fluctuations in the ratio of the two distinct HiNF-D species both during hepatic development and the cell cycle in normal diploid cells, we postulate that this modification of HiNF-D is related to the cell cycle. However, in several tumor-derived and transformed cell types the putative hyperphosphorylated form of HiNF-D is constitutively present. These data suggest that deregulation of a phosphatase-sensitive post-translational modification required for HiNF-D binding is a molecular event that reflects abrogation of a mechanism controlling cell proliferation. Thus, phosphorylation and dephosphosphorylation of histone promoter factors may provide a basis for modulation of protein/DNA interactions and H4 histone gene transcription during the cell cycle and at the onset of quiescence and differentiation.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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