Interestingly, when the biological responses were compared with the binding affinities of the analogs to in-vitro translated human vitamin D receptor and with their ability to protect the receptor against partial proteolytic digestion, significant correlations were not observed. In human MG-63 osteosarcoma cells, quantification of cellular osteocalcin mRNA levels by Northern blot analysis and osteocalcin biosynthesis by radioimmunoassay indicated that most studied analogs at a concentration of 10 nm induced osteocalcin gene expression more efficiently than the parent compound, calcitriol.
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We have compared structure-function relationships of a series of new C-20 epimer (20-epi) vitamin D3 analogs with their. Many of these analogs exhibit lower calcemic effects than calcitriol and inhibit cell proliferation and enhance cell differentation more efficiently than calcitriol. Read moreĪ growing number of calcitriol (1alpha,25-dihydroxyvitamin D3) analogs have become available in recent years.
These results indicate that these two distinct coactivators are differentially involved in Vitamin D regulation of gene transcription during keratinocyte differentiation, suggesting that these coactivators are part of the means by which the temporal sequence of gene expression is regulated during the differentiation process. Both DRIP205 and SRC-3 potentiated Vitamin D-induced transcription in proliferating cells, but during differentiation, DRIP205 was no longer effective. After the cells differentiated, members of the SRC/p160 family were identified in the complex but not major DRIP subunits. Using GST–VDR affinity beads, we have identified the DRIP/mediator complex as the major VDR binding complex in proliferating keratinocytes. However, the relationship between these two classes of coactivators is not clear. interacting proteins (DRIP/mediator) and the p160 steroid receptor coactivator family (SRC/p160), control the actions of nuclear hormone receptors, including the Vitamin D receptor. Two classes of coactivators, the Vitamin D receptor (VDR). Vitamin D, via its active metabolite 1,25-dihydroxyvitamin D (1,25(OH)2D3), controls the proliferation and differentiation of a number of cell types, including keratinocytes, by directly regulating transcription. In general, the preservation of mRNA in tissue specimen and sensitivity of detection systems largely influence the results of mRNA in situ hybridization on surgical pathology materials.Ĭell programs such as proliferation and differentiation involve the sequential activation and repression of gene expression. Choice of the probes and detection methods may influence the results but it is important for pathologists to determine the most appropriate methods in his or her own laboratories based on the facility and budget. Prompt fixation is also important for specimen preparation regardless of fixatives employed. Surgical pathologists should consider these aspects above prior to performing and/or ordering mRNA in situ hybridization. and iv) analyze the expression at mRNA and protein levels if there are discrepancies between these two levels of expression. Biological significance of mRNA in situ hybridization employing surgical pathology materials are summarized as follows i) determine whether immunoreactivity observed by conventional immunohistochemistry represent the gene products produced, stored or bound to receptor, ii) study the localization of the gene products with rapid intracellular half-life, iii) examine the localization of expression when DNA sequences are known but no reliable antibodies are available for immunohistochemistry. The technique is relatively cumbersome and time-consuming and it is important for pathologists to determine in what situations mRNA in situ hybridization can provide important information in surgical pathology materials. MRNA in situ hybridization has provided important information in the various fields of biology and medicine but it is not easy to incorporate the technique to diagnostic pathology laboratories, compared to immunohistochemistry.
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