Hirose F, Yamaguchi M, Matsukage A
Laboratory of Cell Biology, Aichi Cancer Center Research Institute, Nagoya, Japan.
J Biol Chem. 1994 Jan 28;269(4):2937-42.
The expression of the chloramphenicol acetyltransferase gene under control of the 1152-base pair 5'-flanking region (-1107 to +45 nucleotide positions with respect to the major transcription initiation site) of the Drosophila DNA polymerase alpha gene was repressed by cotransfection into Drosophila Kc cells with a zerknüllt (zen)-expressing plasmid as previously observed with the proliferating cell nuclear antigen (PCNA) gene promoter. The expression of the zen resulted in reduction of the abundance of mRNA for the transfected chloramphenicol acetyltransferase gene and also mRNAs for both DNA polymerase alpha and PCNA. Results obtained using various deletion derivatives of the promoter region and chemically synthesized oligonucleotides of the DNA replication-related element (DRE), a positive cis-acting element found in both DNA polymerase alpha and PCNA genes, revealed that the DRE sequences are responsible to repression by Zen protein. The nuclear extract of Kc cells transfected by the zen-expressing plasmid contained lesser amounts of the DRE-binding factor (DREF) than that of untransfected or mutant zen-transfected cells. These results suggest that the Zen protein represses expression of DNA replication-related genes by reducing DREF, although the detailed mechanism of the repression remains to be elucidated.
如之前在增殖细胞核抗原（PCNA）基因启动子中观察到的那样，将氯霉素乙酰转移酶基因置于果蝇DNA聚合酶α基因1152个碱基对的5'侧翼区域（相对于主要转录起始位点为-1107至+45核苷酸位置）控制之下，通过与表达零尾（zen）的质粒共转染到果蝇Kc细胞中，其表达受到抑制。zen的表达导致转染的氯霉素乙酰转移酶基因的mRNA丰度降低，同时也导致DNA聚合酶α和PCNA的mRNA丰度降低。使用启动子区域的各种缺失衍生物以及DNA复制相关元件（DRE）的化学合成寡核苷酸（在DNA聚合酶α和PCNA基因中均发现的一种正向顺式作用元件）所获得的结果表明，DRE序列与Zen蛋白介导的抑制作用有关。用表达zen的质粒转染的Kc细胞的核提取物中，DRE结合因子（DREF）的含量比未转染或用突变zen转染的细胞少。这些结果表明，Zen蛋白通过减少DREF来抑制DNA复制相关基因的表达，尽管抑制的详细机制仍有待阐明。
