Kalvakolanu D V, Liu J, Hanson R W, Harter M L, Sen G C
Department of Molecular Biology, Cleveland Clinic Research Institute, Ohio 44195-5285.
J Biol Chem. 1992 Feb 5;267(4):2530-6.
Adenovirus infection of hepatoma cells inhibited transcription of the phosphoenolpyruvate carboxykinase (GTP) (EC 4.1.1.32) (PEPCK) gene and virtually eliminated transcription of a chimeric gene which contained the PEPCK promoter linked to the structural gene for chloramphenicol acetyltransferase (CAT). This effect is due to the viral protein E1A, since adenovirus containing a deletion in the E1A gene did not repress transcription from the PEPCK promoter. Both the 243R and 283R products of the E1A gene were effective. The conserved region 1 (CR-1) domain of E1A was required for this effect. Treatment of hepatoma cells with 8-bromo-cAMP or transfection with plasmids coding for the catalytic subunit of protein kinase A, CAAT/enhancer binding protein alpha (C/EBP), or Jun, all potent inducers of PEPCK gene transcription, did not relieve the inhibition caused by E1A. This inhibition does not appear to be mediated by major enhancer elements and in the PEPCK gene since transcription from the PEPCK promoter containing block mutations in binding domains for C/EBP and cAMP regulatory element binding protein (CREB) was also inhibited by E1A. Transcription of chimeric genes containing two copies each of the major cAMP response domains (CRE-1 and P-3) linked to a neutral promoter and fused to the CAT structural gene was stimulated by the catalytic subunit of protein kinase A, but this effect was totally inhibited by E1A. The strong repressive effect of E1A on PEPCK gene transcription seems to involve an interruption of an obligatory interaction between factors which bind to the cAMP response element in the PEPCK promoter and the TATA box.
腺病毒感染肝癌细胞可抑制磷酸烯醇式丙酮酸羧激酶（GTP）（EC 4.1.1.32）（PEPCK）基因的转录，并几乎完全消除一个嵌合基因的转录，该嵌合基因包含与氯霉素乙酰转移酶（CAT）结构基因相连的PEPCK启动子。这种效应是由病毒蛋白E1A引起的，因为E1A基因缺失的腺病毒不会抑制PEPCK启动子的转录。E1A基因的243R和283R产物均有效。E1A的保守区域1（CR-1）结构域是产生这种效应所必需的。用8-溴-cAMP处理肝癌细胞或转染编码蛋白激酶A催化亚基、CAAT/增强子结合蛋白α（C/EBP）或Jun的质粒（这些都是PEPCK基因转录的有效诱导剂），均不能缓解E1A引起的抑制作用。这种抑制作用似乎不是由PEPCK基因中的主要增强子元件介导的，因为含有C/EBP和cAMP反应元件结合蛋白（CREB）结合结构域阻断突变的PEPCK启动子的转录也受到E1A的抑制。含有与中性启动子相连并融合到CAT结构基因的两个主要cAMP反应结构域（CRE-1和P-3）拷贝的嵌合基因的转录受到蛋白激酶A催化亚基的刺激，但这种效应被E1A完全抑制。E1A对PEPCK基因转录的强烈抑制作用似乎涉及到与PEPCK启动子中cAMP反应元件结合的因子与TATA盒之间必要相互作用的中断。
