New POU dimer configuration mediates antagonistic control of an osteopontin preimplantation enhancer by Oct-4 and Sox-2
New POU dimer configuration mediates antagonistic control of an osteopontin preimplantation enhancer by Oct-4 and Sox-2
复制标题
DOI：
10.1101/gad.12.13.2073
复制
发表时间：
1998-07-01
影响因子：
10.5
通讯作者：
Schöler, HR
中科院分区：
文献类型：
--
作者：
Botquin, V;Hess, H;Schöler, HR
POU转录因子Oct-4在原肠形成前胚胎的种系、多能细胞和源自早期胚胎的干细胞系中特异性表达。骨桥蛋白（OPN）是一种由植入前胚胎细胞分泌的蛋白质，含有GRGDS基序，可与特定的整合素亚型结合并调节细胞粘附/迁移。我们发现Oct-4和OPN在植入前小鼠胚胎和胚胎细胞系分化过程中共表达。通过Oct-4特异性抗体从胚胎干细胞的共价固定的染色质中免疫沉淀OPN的第一内含子（i-opn），表明Oct-4在体内与该片段结合。i-opn片段在类似于植入前胚胎细胞的细胞系中起增强子的作用。此外，它包含一个新的回文Oct因子识别元件（PORE），它由一对反向的同源结构域结合位点组成，间隔正好为5 bp（ATTTG +5 CAAAT）。POU蛋白可以在PORE上以先前未描述的构型同源二聚化和异源二聚化。OPN元件的强转录激活需要完整的孔。相反，与下游一半的PORE重叠的规范八聚体不是必需的。Sox-2是一种含有HMG盒的转录因子，在早期小鼠胚胎中与Oct-4共表达。Sox-2抑制Oct-4介导的i-opn的激活，通过位于靠近PORE的典型Sox元件。抑制依赖于HMG盒外的Sox-2的羧基末端区域。表达，DNA结合，和反式激活数据是一致的假设，OPN的表达调节Oct-4和Sox-2在植入前的发展。
The POU transcription factor Oct-4 is expressed specifically in the germ line, pluripotent cells of the pregastrulation embryo and stem cell lines derived from the early embryo. Osteopontin (OPN) is a protein secreted by cells of the preimplantation embryo and contains a GRGDS motif that can bind to specific integrin subtypes and modulate cell adhesion/migration. We show that Oct-4 and OPN are coexpressed in the preimplantation mouse embryo and during differentiation of embryonal cell lines. Immunoprecipitation of the first intron of OPN (i-opn) from covalently fixed chromatin of embryonal stem cells by Oct-4-specific antibodies indicates that Oct-4 binds to this fragment in vivo. The i-opn fragment functions as an enhancer in cell lines that resemble cells of the preimplantation embryo. Furthermore, it contains a novel palindromic Oct factor recognition element (PORE) that is composed of an inverted pair of homeodomain-binding sites separated by exactly 5 bp (ATTTG +5 CAAAT). POU proteins can homo- and heterodimerize on the PORE in a configuration that has not been described previously. Strong transcriptional activation of the OPN element requires an intact PORE. In contrast, the canonical octamer overlapping with the downstream half of the PORE is not essential. Sox-2 is a transcription factor that contains an HMG box and is coexpressed with Oct-4 in the early mouse embryo. Sox-2 represses Oct-4 mediated activation of i-opn by way of a canonical Sox element that is located close to the PORE. Repression depends on a carboxy-terminal region of Sox-2 that is outside of the HMG box. Expression, DNA binding, and transactivation data are consistent with the hypothesis that OPN expression is regulated by Oct-4 and Sox-2 in preimplantation development.