AFP基因细胞专一性的表达依赖于某些核蛋白

CELL-SPECIFIC EXPRESSION OF AFP GENE IS DEPEN DENT ON SOME NUCLEAR PROTEINS

Southern blotting分析没有发现成年大鼠肝、胚肝及肝癌细胞AFP基因5′端及上游有任何不同。以AFP基因转录起始点到5′端上游255 bp DNA片段为探针进行Southwestern blotting分析,发现表达AFP基因的细胞核蛋白中存在与其结合的核蛋白,这些在成年大鼠肝、肺、脾、心和肾细胞核蛋白中不存在。含有结合蛋白的肝癌核蛋白部分能使作为RNA聚合酶Ⅱ来源的成年大鼠肝细胞核蛋白部分具备较高的体外转录活性,表明基因细胞专一的表达确与某些结合蛋白有关。

AFP is an oncodevelopmental protein. Its level decreases abruptly after birth and reaches almost undetectable level during normal adult life. However, reexpres-sion of the gene can be observed during hepatocarcinogenesis. To further understand mechanism of regulating AFP expression, we checked several restriction enzyme map of 5' terminal and flanking sequences of AFP gene.There are no differences among adult rat liver,feta 1 liver and hepatoma cells. Using +2-255 bp sequence probe of AFP gene to do southwestern blotting assay, the result showed that the gene-active cells, such as hepa- toma cells, contained binding-proteins which were apparently lacking in adult rat liver, lung, spleen, heart and kindney cells. While the fractions of nuclear proteins from adult rat liver cells were devoid of any stimulatory effect on transcription, those of binding-proteins from hepatoma stimulated the transcription of AFP gene in vitro. The hepatoma binding-proteins can rescue transcription activity of fraction of nuclear proteins from adult rat liver cells. These results indicate that cell-specific expression of AFP gene is regulated by protein-factors.