Mizuno K, Goto M, Masamune Y, Nakanishi Y
Faculty of Pharmaceutical Sciences, Kanazawa University, Ishikawa, Japan.
Gene. 1992 Oct 1;119(2):293-7. doi: 10.1016/0378-1119(92)90286-x.
Phosphoglycerate kinase (PGK), a glycolytic enzyme, possesses two isozymes: somatic-type PGK-1 and testis-specific PGK-2, encoded by distinct genes. Tissue-specific expression of the two PGK-encoding genes (Pgk) seems to be transcriptionally controlled, since tissue distribution of the mRNAs coincides well with that of the proteins. In the present study, we determined the cis-acting DNA elements that regulate the transcription of mouse Pgk-2. A transient expression assay of DNAs having various portions of the Pgk-2 upstream region linked to the chloramphenicol acetyltransferase (CAT)-encoding gene (cat) was performed using mouse cell lines that exclusively express Pgk-1. A substantial increase in cat expression was observed when the region between nucleotides (nt) -1404 and -685, relative to the most distal transcription start point at nt +1, was lost. This cis-acting region appeared to function as a silencer, since it repressed cat expression independently of either orientation to or distance from the Pgk-2 promoter. Moreover, the cis element inhibited Pgk-2 transcription with no effect on Pgk-1 transcription in a cell-free system using nuclear extracts of rat liver. These results suggest that a silencer-like negative cis element is responsible, at least partly, for tissue-specific transcription of Pgk-2.
磷酸甘油酸激酶（PGK）是一种糖酵解酶，有两种同工酶：体细胞型PGK-1和睾丸特异性PGK-2，由不同基因编码。两种PGK编码基因（Pgk）的组织特异性表达似乎受到转录调控，因为mRNA的组织分布与蛋白质的组织分布非常吻合。在本研究中，我们确定了调节小鼠Pgk-2转录的顺式作用DNA元件。使用仅表达PGK-1的小鼠细胞系，对与氯霉素乙酰转移酶（CAT）编码基因（cat）相连的Pgk-2上游区域的不同部分的DNA进行瞬时表达分析。当相对于最远端转录起始点（位于核苷酸+1处）的核苷酸（nt）-1404至-685之间的区域缺失时，观察到cat表达大幅增加。这个顺式作用区域似乎起到沉默子的作用，因为它独立于与Pgk-2启动子的方向或距离来抑制cat表达。此外，在使用大鼠肝脏核提取物的无细胞系统中，该顺式元件抑制Pgk-2转录，而对Pgk-1转录没有影响。这些结果表明，一种类似沉默子的负顺式元件至少部分负责Pgk-2的组织特异性转录。
