DEVELOPMENTAL REGULATION OF RAT SERINE DEHYDRATASE GENE-EXPRESSION - EVIDENCE FOR THE PRESENCE OF A REPRESSOR IN FETAL HEPATOCYTES

To determine why the rat serine dehydratase gene becomes transcription ally activated just after birth, we examined the interactions of DNA b inding proteins of fetal and adult rat livers with the serine dehydrat ase gene promoter by DNase I protection analysis and gel mobility shif t assay. Several binding regions of nuclear proteins were found to be common to fetal and adult livers and interaction of factors with the c haracteristics of Sp1 or NF-Y was suggested. Two additional regions, n amed regions B and I, were specific to fetal liver. These regions cont ain GATA-like sequences and competition experiments by gel mobility sh ift assay suggested that the fetal liver-enriched factor binds to the GATA-like sequences. The function of the regions B and I in transcript ion regulation was investigated in fetal and adult hepatocytes by tran sient DNA transfer experiments with serine dehydratase-chloramphenicol acetyltransferase fusions. These experiments showed that these region s functioned as negative cis-acting elements in fetal hepatocytes, but not in adult hepatocytes.