Turcotte B, Guertin M, Chevrette M, Bélanger L
Nucleic Acids Res. 1985 Apr 11;13(7):2387-98. doi: 10.1093/nar/13.7.2387.
Cloned cDNA fragments spanning nearly the entire coding regions of rat AFP and albumin genes were used in liver nuclear run-off assays. Under standard assay conditions, transcription signals detected with 5' probes were systematically stronger than with 3' probes. Heparin eliminated this phenomenon, which suggests that nuclear run-off assays are subject to in vitro reinitiation occurring preferentially in promoter gene regions. Transcription in the presence of heparin indicates that very few polymerases are engaged on the AFP gene in adult rat liver. Dexamethasone treatment of developing rat liver results in the loss of transcribing polymerases from all regions of the AFP gene. Albumin gene transcription is unaffected. Inhibition of liver protein synthesis with cycloheximide does not modify the AFP gene suppressive action of dexamethasone. Glucocorticoid hormone receptors may thus directly interact with the AFP locus, blocking polymerase initiation. We also report the sequence analysis of rat AFP mRNA, which reveals the existence of two potential initiation codons on this molecule.
跨越大鼠甲胎蛋白（AFP）和白蛋白基因几乎整个编码区的克隆cDNA片段用于肝细胞核延伸转录分析。在标准分析条件下，用5'探针检测到的转录信号系统性地强于用3'探针检测到的信号。肝素消除了这种现象，这表明核延伸转录分析易受体外重新起始的影响，这种重新起始优先发生在启动子基因区域。在肝素存在下的转录表明，成年大鼠肝脏中很少有聚合酶结合在AFP基因上。地塞米松处理发育中的大鼠肝脏会导致AFP基因所有区域的转录聚合酶丢失。白蛋白基因转录不受影响。用环己酰亚胺抑制肝脏蛋白质合成不会改变地塞米松对AFP基因的抑制作用。因此，糖皮质激素受体可能直接与AFP基因座相互作用，阻断聚合酶起始。我们还报告了大鼠AFP mRNA的序列分析，该分析揭示了该分子上存在两个潜在的起始密码子。
