Cloning of cDNA encoding for transcription regulatory factor of the laminin B1 gene

分析了维甲酸诱导F9细胞分化后，层粘连蛋白B1基因转录调控的分子机制。利用体外转录重组系统，我们定义了小鼠层粘连蛋白B1基因的一个新的启动子结构，它由-1到-100之间的三个元件组成。此外，我们的瞬时表达分析表明，层粘连蛋白B1基因的转录被F9细胞分化后诱导的AP-1活性激活。有趣的是，AP-1诱导的转录激活被干细胞特异性负抑制因子取消，该负抑制因子在分化后期消失。因此，推测层粘连蛋白B1基因转录的后期诱导是由AP-1与负性因子共同调控的。我们目前获得了一个编码一个新的孤儿不明受体的cDNA克隆，尽管目前尚不清楚该受体是否参与层粘连蛋白B1基因的转录调控。有趣的是，孤儿受体在小鼠脑内和经RAR诱导分化为神经细胞的P19 EC细胞中均有严格表达，提示孤儿受体可能在中枢神经系统发育和分化过程中的基因表达调控中起关键作用。

Molecular mechanism by which transcription of the laminin B1 gene is regulated after differentiation of F9 cells by retinoic acid have been analyzed. Using in vitro transcription reconstitution system, we defined a novel promoter structure of the murine laminin B1 gene which is consisted of three elements between -1 and -100. Further, we showed from transient expression analysis that transcription of the laminin B1 gene is activated by AP-1 activity induced after F9 cell differentiation. Interestingly, AP-1 induced activation of transcription was abrogated by a stem cell specific negative repressor which disappeared late after the differentiation. Therefore, it was suggested that the late induction of transcription of the laminin B1 gene regulated by AP-1 in concert withthe negative factor. We currently obtained a cDNA clone encoding a novel orphan unclear receptor, although it is not known at present whether this receptor is involved in regulation of transcription of the laminin B1 gene. Interestingly, the orphan receptor was shown to be expressed strictly in mouse brain and in P19 EC cell which was induced to differentiated into neural cells by RA.This suggested that the orphan receptor might play key role in regulation of genes expressing during development and differentiation of central nervous system.