Two of four alternatively spliced isoforms of RUNX2 control osteocalcin gene expression in human osteoblast cells
Two of four alternatively spliced isoforms of RUNX2 control osteocalcin gene expression in human osteoblast cells
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DOI：
10.1016/j.gene.2007.12.025
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发表时间：
2008-04-30
期刊：
影响因子：
3.5
通讯作者：
Hozumi, Nobumichi
中科院分区：
文献类型：
--
作者：
Makita, Naoyuki;Suzuki, Mitsuhiro;Hozumi, Nobumichi
Runx 2是一种Runt结构域转录因子，其转录调节成骨细胞分化和骨形成。在这项研究中，我们表明，人软骨和骨肉瘤细胞系，人间充质干细胞（hMSC）和人原代软骨细胞（HC），成骨细胞（HOb）表达一个完整的同种型（RUNX 2 wt）和3个可变剪接的同种型（RUNX 2 Delta 5，Delta 7和Delta 5 Delta 7），这些同种型是通过跳过外显子5和/或外显子7产生的。RUNX 2的两种截短形式（RUNX 2 Delta 5和RUNX 2 Delta 5 A 7）不定位于细胞核中，并且失去了它们的DNA结合活性。在与骨钙素（OC）启动子构建体的共转染实验中，我们证实，只有RUNX 2 wt和RUNX 2 Delta 7可以上调骨肉瘤细胞系中的OC启动子活性。此外，共激活因子CBP/p300在与RUNX 2 wt或RUNX 2 Delta 7共表达时增强OC启动子的转录活性，但在与RUNX 2 Delta 5或RUNX 2 Delta 5 Delta 7共表达时不增强。相反，辅阻遏物HDAC 3仅在与RUNX 2 wt共表达时抑制OC启动子的激活。这些结果支持的假设，RLTNX 2上调和下调其靶基因启动子，如OC基因，使用各种异构体和上下文依赖性的转录复合物的形成。(c)2008 Elsevier B. V.保留所有权利。
Runx2 is a Runt domain transcription factor that transcriptionally regulates osteoblast differentiation and bone formation. In this study, we show that human chondro- and osteosarcoma cell lines, human mesenchymal stem cells (hMSC) and a human primary chondrocytes (HC), osteoblst cells (HOb) express an intact isoform (RUNX2wt) and 3 alternatively spliced isoforms (RUNX2 Delta 5, Delta 7, and Delta 5 Delta 7) that are generated by skipping exon 5 and/or exon 7. Two of the truncated forms of RUNX2 (RUNX2 Delta 5 and RUNX2 Delta 5 A 7) did not localize in the nucleus and had lost their DNA binding activity. In cotransfection experiments with an osteocalcin (OC) promoter construct, we confirmed that only RUNX2wt and RUNX2 Delta 7 could upregulate the OC promoter activity in the osteosarcoma cell line. In addition, the coactivator CBP/p300 enhanced the transcriptional activity of the OC promoter when coexpressed with RUNX2wt or RUNX2 Delta 7, but not when coexpressed with RUNX2 Delta 5 or RUNX2 Delta 5 Delta 7. In contrast, the corepressor HDAC3 only repressed the activation from the OC promoter when coexpressed with RUNX2wt. These results support the hypothesis that RLTNX2 both up- and downregulates its target gene promoters, as exemplified by the OC gene, using various isoforms and context-dependent formation of transcriptional complexes. (c) 2008 Elsevier B.V. All rights reserved.