Montecino M, Lian J, Stein G, Stein J
Department of Cell Biology, University of Massachusetts Medical Center, Worcester, 01655, USA.
Biochemistry. 1996 Apr 16;35(15):5093-102. doi: 10.1021/bi952489s.
Transcription of the osteocalcin gene, which encodes a 10 kDa bone-specific protein, is controlled by modularly organized basal regulatory sequences and hormone-responsive enhancer elements. We have previously shown that in the ROS 17/2.8 rat osteosarcoma cell line, which continuously expresses the osteocalcin gene, key regulatory elements reside in two DNase I hypersensitive sites that are fucntionally correlated with transcriptional activity. We now report that a specific nucleosomal organization supports this constitutive expression in ROS 17/2.8 cells, and that chromatin remodeling directly correlates with the developmentally regulated transcriptional activation of the osteocalcin gene during differentiation of normal diploid rat osteoblasts. By combining DNase I, micrococcal nuclease, and specific restriction endonuclease digestion analysis, we observed that the presence of DNAse I hypersensitive sites (-170 to -70 and -600 to -400) and a selective nucleosome positioning over the OC gene promoter are directly associated with developmental stage-specific transcriptional activation in bone-derived cells.
骨钙素基因编码一种10 kDa的骨特异性蛋白，其转录受模块化组织的基础调控序列和激素反应增强子元件控制。我们之前已经表明，在持续表达骨钙素基因的ROS 17/2.8大鼠骨肉瘤细胞系中，关键调控元件位于两个与转录活性功能相关的DNase I超敏位点。我们现在报告，一种特定的核小体组织支持ROS 17/2.8细胞中的这种组成型表达，并且染色质重塑与正常二倍体大鼠成骨细胞分化过程中骨钙素基因的发育调控转录激活直接相关。通过结合DNase I、微球菌核酸酶和特异性限制性内切酶消化分析，我们观察到DNase I超敏位点（-170至-70和-600至-400）的存在以及OC基因启动子上的选择性核小体定位与骨源性细胞中发育阶段特异性转录激活直接相关。
