Structure and Expression of Hepatocyte Growth Factor (HGF)

1)大鼠肝细胞生长因子基因结构我们从大鼠基因组文库中分离出编码HGF全区域的大鼠基因组克隆。大鼠HGF编码于约70 kbp的基因组区域，分为18个外显子。测定了其启动子区域和每个外显子与内含子之间的侧翼区域的完整核苷酸序列。在启动子区域，没有观察到TATA和GC盒序列，因此大鼠HGF启动子可能具有独特的特性。各种增强子有一些一致的序列，如AP1和Sp1结合位点、APRF和NF-1。特别是APRF元件的存在，提示HGF的表达受细胞因子的调控。通过s1保护和引物延伸分析，发现HGF启动子区域至少有4个转录起始位点。CC14诱导肝炎时，来自第3起始位点（B位点）的转录显著增加，说明B位点的转录调控对损伤中HGF的表达起重要作用。2) HGF表达检测系统的建立为了建立HGF诱导机制的检测系统，我们尝试培养非实质细胞。到目前为止，我们已经开发了分离和培养非实质肝细胞的方法。

1) Structure of the rat hepatocyte growth factor geneWe isolated the rat genomic clones coding the whole region of HGF from rat genomic library. The rat HGF is encoded in about 70 kbp genomic region and divided into 18 exons. The complete nucleotide sequences of its promoter region and the flanking regions between each exons and introns were determined. In the promoter region, the TATA and GC box sequences are not observed so that the promoter of rat HGF may has unique characters. There are some consensus sequences of various enhancer, such as AP1 and Sp1 binding site, APRF, and NF-1. Especially, the existence of APRF elements suggest that the expression of HGF are regulated by cytokines.By S1-protection and primer-extension analysis, it is found that there are at least four transcription start sites in HGF promoter region. When hepatitis was induced by CC14, the transcription from the 3rd start site (site B) increased dramatically, indicating that the transcriptional regulation from site B is an important for the expression of HGF in the injury.2) Development of the assay systems for HGF expressionTo establish the assay systems of HGF induction mechanisms, we try to culture the non-parenchymal cells. Until now, we have developed the method for the separation and the culture of the non-parenchymal livercells.