JEM-1, a novel nuclear co-factor: localisation and functional interaction with AP-1
JEM-1, a novel nuclear co-factor: localisation and functional interaction with AP-1
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DOI：
10.1038/sj.leu.2401560
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发表时间：
1999-12
期刊：
影响因子：
11.4
通讯作者：
J. Tong;E. Duprez;M. Lanotte
中科院分区：
文献类型：
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作者：
J. Tong;E. Duprez;M. Lanotte
JEM-1是类视黄醇治疗诱导急性早幼粒细胞白血病（APL） mRNA表达的新基因。该基因产物是一个45 kDa的含有亮氨酸重复序列的基本核因子，在HeLa或COS-7细胞中短暂表达，并在细胞核内以精细的间断结构进行免疫表征，细胞转染后其大小增加。核仁中未表达Jem-1。实验发现，Jem-1的肽域（JemΔ 331 - 400和Jem ΔL 179 - 206）缺失表明其c端序列（Thr 331→Leu 400）是核易位所必需的，而亮氨酸重复结构域（Arg 179→Glu 206）对亚细胞定位没有影响。在含有pml的核体或含有剪接因子SC-35的斑点结构中未检测到Jem-1蛋白。相反，它定位于细胞核中含有激活蛋白-1 （AP-1）的结构。DNA迁移位移实验表明，体外翻译的Jem蛋白既不与AP-1的DNA结合位点相互作用，也不直接与与该特定序列结合的体外共翻译c-Fos或/和c-Jun蛋白相互作用。有趣的是，通过含有人胶原酶基因AP-1结合位点的异源启动子驱动的CAT报告基因测量，em-1-1显著增加了c-Jun的转录活性（3倍），并且更强烈地增加了异位共表达的c-Fos和c-Jun的转录活性（5至6倍）。这些协同效应强烈依赖于杰姆-1的剂量。然而，Jem-1单独对胶原酶启动子没有活性。em-1的亮氨酸重复序列（Arg 179→Glu 206）的缺失并未降低em-1对AP-1活性的增强能力。相反，当em-1的c端（Thr 331→Leu 400）被删除时，AP-1活性的增强被取消。我们得出结论，JEM-1基因的45 kDa核产物具有一种新的转录辅因子的特征，该转录辅因子可以增强AP-1的活性，而不直接与c-Jun或c-Fos蛋白相互作用。讨论了这些发现对APL细胞成熟的可能影响。
JEM-1 is a novel gene whose mRNA expression in acute promyelocytic leukemia (APL) is induced by retinoid treatments. The gene product, a 45 kDa basic nuclear factor containing a leucine repeat, was transiently expressed in HeLa or COS-7 cells and immunocharacterized within the nuclei in fine punctuated structures which increase in size after cell transfection. Jem-1 was not expressed in the nucleoli. Experimental deletion of peptide domains of Jem-1 (JemΔ 331–400 and Jem ΔL 179–206) showed that its C-terminal sequence (Thr 331→ Leu 400) is required for nuclear translocation, while the leucine repeat domain (Arg 179→ Glu 206) has no influence on subcellular localization. The Jem-1 protein was not detected in the PML-containing nuclear bodies or in speckled structures containing the splicing factor SC-35. In contrast it was localized in the nucleus in structures containing activator protein-1 (AP-1). DNA mobility shift assays showed that the in vitro translated Jem protein interacts neither with the DNA binding site of AP-1, nor directly with in vitro co-translated c-Fos or/and c-Jun proteins bound to this specific sequence. Interestingly, Jem-1-1 increased substantially the transcriptional activity of c-Jun (three-fold) and more strongly that of ectopically co-expressed c-Fos and c-Jun (five-to six-fold), as measured by a CAT reporter gene driven by a heterologous promoter containing the AP-1 binding site of the human collagenase gene. These synergistic effects were strongly Jem-1 dose-dependent. However, Jem-1 alone showed no activity on the collagenase promoter. A deletion of the leucine repeat of Jem-1 (Arg 179→ Glu 206) did not diminish the enhancer capacity of Jem-1 on AP-1 activity. In contrast, the enhanced AP-1 activity was abrogated when Jem-1 was deleted of its C-terminus (Thr 331→ Leu 400). We conclude that the 45 kDa nuclear product of the JEM-1 gene has features of a novel transcription cofactor, which is enhancing AP-1 activity without directly interacting with c-Jun or c-Fos proteins. Possible implications of these findings for APL cell maturation are discussed.