Delva Laurent, Gallais Isabelle, Guillouf Christel, Denis Nicole, Orvain Christophe, Moreau-Gachelin Francoise
Inserm U528, Section de recherche, Institut Curie, Paris, France.
Oncogene. 2004 May 27;23(25):4389-99. doi: 10.1038/sj.onc.1207578.
The hematopoietic transcription factor Spi-1/PU.1 is an oncoprotein participating to the malignant transformation of proerythroblasts in the Friend erythroleukemia or in the erythroleukemic process developed in spi-1 transgenic mice. Overexpression of Spi-1 in proerythroblasts blocks their differentiation. We have shown that Spi-1 promotes the use of the proximal 5'-splice site during the E1A pre-mRNA splicing and interferes with the effect of TLS (Translocated in LipoSarcoma) in this splicing assay. TLS was identified from chromosomal translocations in human liposarcoma and acute myeloid leukemia. Here, we determine the function of Spi-1 domains in splicing and in the interference with TLS. In transient transfection assays in erythroid cells, we show that the DNA binding domain cooperates with the transactivation domain or the PEST region of Spi-1 to modify the function of TLS in splicing. Interestingly, the 27 C-terminal amino acids, which determine the DNA binding activity of Spi-1, are necessary for the splicing function of Spi-1 as well as for its ability to interfere with TLS. Finally, we demonstrate that in leukemic proerythroblasts overexpressing Spi-1, TLS has lost its splicing effect. Thus, we hypothesize that oncogenic pathways in proerythroblasts may involve the ability of Spi-1 to alter splicing.
造血转录因子Spi-1/PU.1是一种癌蛋白，参与Friend红白血病中早幼红细胞的恶性转化，或在spi-1转基因小鼠中发生的红白血病过程。早幼红细胞中Spi-1的过表达会阻断其分化。我们已经表明，在E1A前体mRNA剪接过程中，Spi-1促进近端5'-剪接位点的使用，并在该剪接试验中干扰TLS（易位至脂肪肉瘤）的作用。TLS是从人类脂肪肉瘤和急性髓系白血病的染色体易位中鉴定出来的。在这里，我们确定了Spi-1结构域在剪接以及对TLS干扰中的功能。在红系细胞的瞬时转染试验中，我们表明DNA结合结构域与Spi-1的反式激活结构域或PEST区域协同作用以改变TLS在剪接中的功能。有趣的是，决定Spi-1 DNA结合活性的27个C末端氨基酸对于Spi-1的剪接功能及其干扰TLS的能力是必需的。最后，我们证明在过表达Spi-1的白血病早幼红细胞中，TLS失去了其剪接作用。因此，我们推测早幼红细胞中的致癌途径可能涉及Spi-1改变剪接的能力。
