Subunits of the heterotrimeric transcription factor NF-Y are imported into the nucleus by distinct pathways involving importin β and importin 13
Subunits of the heterotrimeric transcription factor NF-Y are imported into the nucleus by distinct pathways involving importin β and importin 13
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DOI：
10.1128/mcb.25.13.5339-5354.2005
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发表时间：
2005-07-01
影响因子：
5.3
通讯作者：
Albig, W
中科院分区：
文献类型：
--
作者：
Kahle, J;Baake, M;Albig, W
转录激活因子Nf-Y是由Nf-YA、Nf-YB和Nf-YC组成的异源三聚体复合体，与约30%的真核启动子中存在的CCAAT共识特异结合。这三个亚基都含有进化上保守的核心区，在NF-YB和NF-YC的情况下，核心区包含一个组蛋白折叠基序(HIM)。我们的体外结合研究和核进口试验的结果揭示了核因子-Y亚基的两种不同的运输机制。当NF-YA通过Importin P介导的途径导入时，NF-YB/NF-YC异源二聚体以Importin 13依赖的方式转位到细胞核中。我们在NF-YA中定义了一个非经典的核定位信号(NcNLS)，突变分析表明，ncNLS中的正电荷氨基酸残基是NF-YA核靶向所必需的。Importin P结合仅限于单体的、非复杂的NF-YA亚单位。相比之下，核进口的核因子-YB和核因子-YC需要形成二聚体。Importin 13只识别NF-YB/NF-YC二聚体，而不识别单体成分，并将其输入到细胞核中。Importin 13与NF-YA竞争结合NF-YB/NF-YC二聚体。我们的数据表明，从两个亚基的HIM衍生的一个不同的结合平台，NF-YB/NF-YC，介导了这些相互作用。
The transcriptional activator NF-Y is a heterotrimeric complex composed of NF-YA, NF-YB, and NF-YC, which specifically binds the CCAAT consensus present in about 30% of eukaryotic promoters. All three subunits contain evolutionarily conserved core regions, which comprise a histone fold motif (HIM) in the case of NF-YB and NF-YC. Our results of in vitro binding studies and nuclear import assays reveal two different transport mechanisms for NF-Y subunits. While NF-YA is imported by an importin P-mediated pathway, the NF-YB/NF-YC heterodimer is translocated into the nucleus in an importin 13-dependent manner. We define a nonclassical nuclear localization signal (ncNLS) in NF-YA, and mutational analysis indicates that positively charged amino acid residues in the ncNLS are required for nuclear targeting of NF-YA. Importin P binding is restricted to the monomeric, uncomplexed NF-YA subunit. In contrast, the nuclear import of NF-YB and NF-YC requires dimer formation. Only the NF-YB/NF-YC dimer, but not the monomeric components, are recognized by importin 13 and are imported into the nucleus. Importin 13 competes with NF-YA for binding to the NF-YB/NF-YC dimer. Our data suggest that a distinct binding platform derived from the HIM of both subunits, NF-YB/NF-YC, mediates those interactions.