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  • 1
    Electronic Resource
    Electronic Resource
    The osteocalcin gene: a model for multiple parameters of skeletal-specific transcriptional control (1997)
    Springer
    Molecular biology reports 24 (1997), S. 185-196 
    Details
    ISSN: 1573-4978
    Keywords: chromatin structure ; differentiation ; nuclear matrix ; osteoblast ; transcription ; vitamin D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Influences of promoter regulatory elements that are responsive to basal and tissue-restricted transactivation factors, steroid hormones, growth factors and other physiologic mediators has provided the basis for understanding regulatory mechanisms contributing to developmental expression of osteocalcin, tissue specificity and biological activity (reviewed in [1–3]). These regulatory elements and cognate transcription factors support postproliferative transcriptional activation and steroid hormone (e.g. vitamin D) enhancement at the onset of extracellular matrix mineralization during osteoblast differentiation. Three parameters of nuclear structure contribute to osteocalcin gene transcriptional control. The linear representation of promoter elements provides competency for physiological responsiveness within the contexts of developmental as well as phenotype-dependent regulation. Chromatin structure and nucleosome organization reduce distances between independent regulatory elements providing a basis for integrating components of transcriptional control. The nuclear matrix supports gene expression by imposing physical constraints on chromatin related to three dimensional genomic organization. In addition, the nuclear matrix facilitates gene localization as well as the concentration and targeting of transcription factors. Several lines of evidence are presented which are consistent with involvement of multiple levels of nuclear architecture in tissue-specific gene expression during differentiation. Growth factor and steroid hormone responsive modifications in chromatin structure, nucleosome organization and the nuclear matrix are considered which influence transcription of the bone tissue-specific osteocalcin gene during progressive expression of the osteoblast phenotype.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006803615430
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  • 2
    Electronic Resource
    Electronic Resource
    The integrated activities of IRF-2 (HiNF-M), CDP/cut (HiNF-D) and H4TF-2 (HiNF-P) regulate transcription of a cell cycle controlled human histone H4 gene: mechanistic differences between distinct H4 genes (1998)
    Springer
    Molecular biology reports 25 (1998), S. 1-12 
    Details
    ISSN: 1573-4978
    Keywords: histone H4 ; cell cycle ; interferon regulatory factor ; homeodomain protein ; transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Maximal transcription of a prototypical cell cycle controlled histone H4 gene requires a proliferation-specific in vivo genomic protein/DNA interaction element, Site II. Three sequence-specific transcription factors interact with overlapping recognition motifs within Site II: interferon regulatory factor IRF-2 (HiNF-M), the putative H4 subtype-specific protein H4TF-2 (HiNF-P), and HiNF-D which represents a complex of the homeodomain protein CDP/cut, CDC2, cyclin A and pRB. However, natural sequence variation in the Site II sequences of different human H4 genes abolishes binding of specific trans-acting factors; the functional consequences of these variations have not been investigated. To address the precise contribution of H4 promoter factors to the level of H4 gene transcription, we performed a systematic mutational analysis of Site II transcriptional motifs. These mutants were tested for ability to bind each of the Site II cognate proteins, and subsequently evaluated for ability to confer H4 transcriptional activity using chimeric H4 promoter/CAT fusion constructs in different cell types. We also analyzed the effect of over-expressing IRF-2 on CAT reporter gene expression driven by mutant H4 promoters and assessed H4 transcriptional control in cells nullizygous for IRF-1 and IRF-2. Our results show that the recognition sequence for IRF-2 (HiNF-M) is the dominant component of Site II and modulates H4 gene transcription levels by 3 fold. However, the overlapping recognition sequences for IRF-2 (HiNF-M), H4TF-2 (HiNF-P) and CDP/cut (HiNF-D) together modulate H4 gene transcription levels by at least an order of magnitude. Thus, maximal activation of H4 gene transcription during the cell cycle in vivo requires the integrated activities of multiple transcription factors at Site II. We postulate that the composite organization of Site II supports responsiveness to multiple signalling pathways modulating the activities of H4 gene transcription factors during the cell cycle. Variations in Site II sequences among different H4 genes may accomodate differential regulation of H4 gene expression in cells and tissues with unique phenotypic properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006888731301
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  • 3
    Electronic Resource
    Electronic Resource
    Nuclear architecture supports integration of physiological regulatory signals for transcription of cell growth and tissue-specific genes during osteoblast differentiation (1994)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 55 (1994), S. 4-15 
    Details
    ISSN: 0730-2312
    Keywords: nucleus ; gene expression ; cell growth ; osteoblast ; nucleosome ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: During the past several years it has become increasingly evident that the three-dimensional organization of the nucleus plays a critical role in transcriptional control. The principal theme of this prospect will be the contribution of nuclear structure to the regulation of gene expression as functionally related to development and maintenance of the osteoblast phenotype during establishment of bone tissue-like organization. The contributions of nuclear structure as it regulates and is regulated by the progressive developmental expression of cell growth and bone cell related genes will be examined. We will consider signalling mechanisms that integrate the complex and interdependent responsiveness to physiological mediators of osteoblast proliferation and differentiation. The focus will be on the involvement of the nuclear matrix, chromatin structure, and nucleosome organization in transcriptional control of cell growth and bone cell related genes. Findings are presented which are consistent with involvement of nuclear structure in gene regulatory mechanisms which support osteoblast differentiation by addressing four principal questions: (1) Does the representation of nuclear matrix proteins reflect the developmental stage-specific requirements for modifications in transcription during osteoblast differentiation? (2) Are developmental stage-specific transcription factors components of nuclear matrix proteins? (3) Can the nuclear matrix facilitate interrelationships between physiological regulatory signals that control transcription and the integration of activities of multiple promoter regulatory elements? (4) Are alterations in gene expression and cell phenotypic properties in transformed osteoblasts and osteosarcoma cells reflected by modifications in nuclear matrix proteins? There is a striking representation of nuclear matrix proteins unique to cells, tissues as well as developmental stages of differentiation, and tissue organization. Together with selective association of regulatory molecules with the nuclear matrix in a growth and differentiation-specific manner, there is a potential for application of nuclear matrix proteins in tumor diagnosis, assessment of tumor progression, and prognosis of therapies where properties of the transformed state of cells is modified. It is realistic to consider the utilization of nuclear matrix proteins for targeting regions of cell nuclei and specific genomic domains on the basis of developmental phenotypic properties or tissue pathology. © 1994 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240550103
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  • 4
    Electronic Resource
    Electronic Resource
    Bone tissue-specific transcription of the osteocalcin gene: Role of an activator osteoblast-specific complex and suppressor hox proteins that bind the OC box (1996)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 61 (1996), S. 310-324 
    Details
    ISSN: 0730-2312
    Keywords: osteocalcin ; transcriptional regulation ; homeodomain protein ; Msx ; bone-specific ; OC box ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Bone-specific expression of the osteocalcin gene is transcriptionally controlled. Deletion analysis of osteocalcin promoter sequences by transient transfection of osseous (ROS 17/2.8) and nonosseous (R2 fibroblast) cells revealed that the most proximal 108 nucleotides are sufficient to confer tissue-specific expression. By gel mobility shift assays with wild-type and mutated oligonucleotides and nuclear extracts from several different cell lines we identified a novel transcription factor complex which exhibits sequence-specific interactions with the primary transcriptional element, the OC box (nt -99 to -76). This OC box binding protein (OCBP) is present only in osteoblast-like cells. Methylation interference demonstrated association of the factor with OC box sequences overlapping the Msx homeodomain consensus binding site. By assaying several mutations of the OC box, both in gel shift and transient transfection studies using ROS 17/2.8, we show the following. First, binding of OCBP correlates with osteocalcin promoter activity in ROS 17/2.8 cells. Increased binding leads to a 2-3-fold increase in transcription, while decreased binding results in transcription 30-40% of control. Second, homeodomain protein binding suppresses transcription. However, Msx expression is critical for full development of the bone phenotype as determined by antisense studies. Last, we show that one of the mutations of the OC box permits expression of osteocalcin in non-osseous cell lines. In summary, we demonstrate association of at least two classes of tissue-restricted transcription factors with the OC box element, the OCBP and Msx proteins, supporting the concept that these sequences contribute to defining tissue specificity. © 1996 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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