Nmi protein interacts with regions that differ between MycN and Myc and is localized in the cytoplasm of neuroblastoma cells in contrast to nuclear MycN
Nmi protein interacts with regions that differ between MycN and Myc and is localized in the cytoplasm of neuroblastoma cells in contrast to nuclear MycN
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DOI：
10.1038/sj.onc.1203090
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发表时间：
1999-11-18
期刊：
影响因子：
8
通讯作者：
Schwab, M
中科院分区：
文献类型：
--
作者：
Bannasch, D;Weis, I;Schwab, M
Myc家族蛋白在细胞增殖、分化、凋亡和转化等过程中发挥重要作用。Myc的相互作用伙伴有Max、p107、TBP、YY 1、Miz-1、AP-2和Nmi等。Max和Nmi也与MycN结合。与Max与Myc家族蛋白的明确结合相反，Nmi与Myc或MycN的相互作用的特征很差。通过采用酵母双杂交系统，我们已经绘制了负责结合Nmi的MycN和Myc区域。对于MycN，仅中心区域介导与Nmi的结合。相比之下，对于Myc，蛋白质的C-末端部分以及可能的中心部分参与Nmi相互作用。Nmi不与Max相互作用，并且在酵母中没有反式激活能力，这表明Nmi单独在哺乳动物细胞中不是转录激活因子。免疫荧光显示，在293胚胎肾细胞和凯利神经母细胞瘤细胞中，所有可检测到的异位表达的NMI定位于细胞质中，部分以点状，颗粒状模式。MycN，这是高度表达的凯利细胞扩增后，似乎是专门定位在细胞核中。这直接表明，在同一细胞中，至少大部分MycN和Nmi位于不同的细胞区室中。这一结果通过以下发现得到证实：仅在用干扰素γ刺激后在Kelly细胞中表达的内源性Nmi仅在这些细胞的细胞质中检测到。因此，只有非常少量的MycN和Nmi可能参与体内MycN/Nmi相互作用。
Myc family proteins play an important role in cellular processes such as proliferation, differentiation, apoptosis and transformation. A number of interaction partners of Myc have been identified, such as Max, p107, TBP, YY1, Miz-1, AP-2 and Nmi. Both Max and Nmi also bind to MycN. In contrast to the well defined binding of Max to Myc family proteins the interaction of Nmi with Myc or MycN is only poorly characterized. By employing the yeast two-hybrid system we have mapped the regions of MycN and Myc responsible for binding to Nmi. For MycN exclusively a central region mediates binding to Nmi. In contrast, for Myc a C-terminal portion of the protein, and possibly also a central part, is involved in Nmi interaction. Nmi does not interact with Max and has no transactivation capabilities in yeast, suggesting that Nmi alone is not a transcriptional activator in mammalian cells. Immunofluorescence demonstrates that both in 293 embryonic kidney cells and in Kelly neuroblastoma cells all detectable ectopically expressed Nmi is localized in the cytoplasm, in part in a punctate, granular pattern. MycN, which is highly expressed in Kelly cells consequent to amplification, appears to be localized exclusively in the nuclei. This directly demonstrates that in the same cell at least the major proportion of MycN and Nmi is localized in different cellular compartments. This result is confirmed by the finding that endogenous Nmi, which is expressed in Kelly cells only after stimulation with interferon gamma, is detected exclusively in the cytoplasm of these cells. Therefore only a very small amount of MycN and Nmi is likely to be involved in MycN/Nmi interaction in vivo.