Molecular mechanisms of BSP gene transcription on cementblast

骨涎蛋白（Bone Sialoprotein， BSP）是一种组织特异性的骨水泥母细胞标记物，已被证明是由Hertwig上皮细胞转化而来的。为了阐明基因的转录机制，我们研究了3个假定的成骨细胞特异性元件2共识基序（OSE2-1~OSE2-3） Runx2与同源顺式作用元件的相互作用能力。强制表达Runx2诱导OSE2-2串联重复6倍时转录活性增强14倍，OSE2-3串联重复6倍时转录活性增强3倍，而OSE2-1串联重复6倍时转录活性显著降低60%。染色质免疫沉淀分析显示，在体内，Runx2被OSE2-2募集的数量明显高于其他ose2。BMP-2增加了Runx2与这些OSE2s的结合及其转录，而tgf - β 1诱导的OSE2-2转录明显减少。这些数据表明，tgf - β /BMP信号调节了Runx2对各自OSE2s上染色质的协调调节。

Bone Sialoprotein(BSP) is a tissue-specific marker of cementblast cells which has shown to be transformed from Hertwig's epithlial cells.To elucidate the mechanisms of gene transcription,3 putative osteoblast specific element 2 consensus motif(OSE2-1~OSE2-3) were investigated the ability of Runx2 to interact with cognate cis-acting elements. Forced expression of Runx2 induced 14 fold enhancement of transcription activity observed with the 6 x tandem repeats of OSE2-2 and 3 fold enhancement with that of OSE2-3, whereas 60% significant reduction was observed with that of OSE2-1. Chromatin immunorecipitation analyses revealed Runx2 were significantly higher recruited to OSE2-2 than to other OSE2s in vivo. BMP-2 increased Runx2 binding to these OSE2s and its transcription, whereas obvious reduction of OSE2-2 transcription induced by TGF-beta 1. These data suggested that the coordinated regulation of chromatin on respective OSE2s with Runx2 were modulated by TGF-beta/BMP signals.