Yamada A, Takaki S, Hayashi F, Georgopoulos K, Perlmutter R M, Takatsu K
Division of Immunology, Department of Microbiology and Immunology, the Institute of Medical Science, the University of Tokyo, Minato-ku, Tokyo 108-8639, Japan.
J Biol Chem. 2001 May 25;276(21):18082-9. doi: 10.1074/jbc.M008387200. Epub 2001 Mar 13.
The lck gene encodes a protein-tyrosine kinase that plays a key role in signaling mediated through T cell receptor (TCR) and pre-TCR complexes. Transcription of the lck gene is regulated by two independent promoter elements: the proximal and distal promoters. Previous studies employing transgenic mice demonstrated that the sequence between -584 and -240 from the transcription start site in the mouse lck proximal promoter is required for its tissue-specific expression in the thymus. In this study, we demonstrate that a Krüppel-like zinc finger protein, mtbeta (BFCOL1, BERF-1, ZBP-89, ZNF148), previously cloned as a protein that binds to the CD3delta gene enhancer, binds to the -365 to -328 region of the lck proximal promoter. mtbeta is ubiquitously expressed in various cell lines and mouse tissues. Overexpressed mtbeta is more active in T-lineage cells than B-lineage cells for transactivating an artificial promoter consisting of the mtbeta binding site and a TATA box. Activity of the lck proximal promoter was significantly impaired by mutating the mtbeta binding site or by reducing mtbeta protein expression level by using antisense mRNA. Our results indicate that mtbeta activity is regulated in a tissue-specific manner and that mtbeta is a critical transactivator for the lck proximal promoter.
lck基因编码一种蛋白酪氨酸激酶，其在通过T细胞受体（TCR）和前TCR复合物介导的信号传导中起关键作用。lck基因的转录受两个独立的启动子元件调控：近端启动子和远端启动子。先前利用转基因小鼠进行的研究表明，小鼠lck近端启动子转录起始位点上游-584至-240之间的序列是其在胸腺中组织特异性表达所必需的。在本研究中，我们证明了一种先前作为与CD3δ基因增强子结合的蛋白被克隆的Krüppel样锌指蛋白mtbeta（BFCOL1、BERF-1、ZBP-89、ZNF148），可与lck近端启动子的-365至-328区域结合。mtbeta在各种细胞系和小鼠组织中普遍表达。过表达的mtbeta在T系细胞中比在B系细胞中对由mtbeta结合位点和TATA盒组成的人工启动子具有更强的反式激活活性。通过突变mtbeta结合位点或使用反义mRNA降低mtbeta蛋白表达水平，lck近端启动子的活性显著受损。我们的结果表明，mtbeta的活性以组织特异性方式受到调控，并且mtbeta是lck近端启动子的关键反式激活因子。
