Cell transformation mediated by homodimeric E2A-HLF transcription factors.
Cell transformation mediated by homodimeric E2A-HLF transcription factors.
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由同源二聚体 E2A-HLF 转录因子介导的细胞转化。
DOI：
10.1128/mcb.17.3.1417
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发表时间：
1997
影响因子：
5.3
通讯作者：
Look,AT
中科院分区：
文献类型：
--
作者：
Inukai,T;Inaba,T;Yoshihara,T;Look,AT
E2 A-HLF融合基因由原B淋巴细胞中t（17;19）（q22;p13）染色体易位产生，编码一种致癌蛋白，其中E2 A反式激活结构域与肝白血病因子（HLF）的DNA结合和蛋白质二聚化结构域相连，HLF是bZIP转录因子中富含脯氨酸和酸性氨基酸（PAR）亚家族的成员。该融合产物不仅作为同二聚体结合其DNA识别位点，而且作为异二聚体与HLF和PAR bZIP亚家族的两个其他成员，促甲状腺细胞胚胎因子（TEF）和白蛋白启动子D-box结合蛋白（DBP）结合。因此，E2 A-HLF可以通过同源二聚体或异源二聚体复合物直接调节下游靶基因，或通过将正常PAR蛋白隔离为非功能性异源复合物（显性负干扰）来转化细胞。为了区分这些模型，我们构建了突变体E2 A-HLF蛋白，其中HLF的亮氨酸拉链结构域延长了一个螺旋转角或改变了关键的带电氨基酸，使嵌合体能够与DNA结合为同源二聚体，而不是与HLF或其他PAR蛋白的异源二聚体。当将锌诱导型载体引入NIH 3 T3细胞时，这些突变体中的每一个都与未改变的E2 A-HLF一样有效地诱导锚定非依赖性生长，这表明嵌合癌蛋白可以以其同二聚体形式转化细胞。转化也依赖于一个完整的E2 A激活区域，提供了进一步的支持，为功能获得的贡献，而不是一个基于显性干扰或显性负性机制的肿瘤发生。因此，E2 A-HLF及其突变体在NIH 3 T3细胞中的致瘤作用有利于一个简单的模型，其中E2 A-HLF同源二聚体直接结合下游靶基因的启动子/增强子元件，并改变其在早期B细胞祖细胞中的表达模式。
TheE2A-HLFfusion gene, created by the t(17;19)(q22;p13) chromosomal translocation in pro-B lymphocytes, encodes an oncogenic protein in which the E2Atrans-activation domain is linked to the DNA-binding and protein dimerization domain of hepatic leukemia factor (HLF), a member of the proline- and acidic amino acid-rich (PAR) subfamily of bZIP transcription factors. This fusion product binds to its DNA recognition site not only as a homodimer but also as a heterodimer with HLF and two other members of the PAR bZIP subfamily, thyrotroph embryonic factor (TEF) and albumin promoter D-box binding protein (DBP). Thus, E2A-HLF could transform cells by direct regulation of downstream target genes, acting through homodimeric or heterodimeric complexes, or by sequestering normal PAR proteins into nonfunctional heterocomplexes (dominant-negative interference). To distinguish among these models, we constructed mutant E2A-HLF proteins in which the leucine zipper domain of HLF was extended by one helical turn or altered in critical charged amino acids, enabling the chimera to bind to DNA as a homodimer but not as a heterodimer with HLF or other PAR proteins. When introduced into NIH 3T3 cells in a zinc-inducible vector, each of these mutants induced anchorage-independent growth as efficiently as unaltered E2A-HLF, indicating that the chimeric oncoprotein can transform cells in its homodimeric form. Transformation also depended on an intact E2A activator region, providing further support for a gain-of-function contribution to oncogenesis rather than one based on a dominant-interfering or dominant-negative mechanism. Thus, the tumorigenic effects of E2A-HLF and its mutant forms in NIH 3T3 cells favor a straightforward model in which E2A-HLF homodimers bind directly to promoter/enhancer elements of downstream target genes and alter their patterns of expression in early B-cell progenitors.