Nuclear import of the BTB/POZ transcriptional regulator Kaiso
Nuclear import of the BTB/POZ transcriptional regulator Kaiso
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DOI：
10.1242/jcs.01541
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发表时间：
2004-12-01
影响因子：
4
通讯作者：
Daniel, JM
中科院分区：
文献类型：
--
作者：
Kelly, KF;Otchere, AA;Daniel, JM
Kaiso是一种BTB/POZ转录因子，在体外作为基质金属蛋白酶基因matrilysin和非经典Wnt信号传导基因Wnt-11的转录阻遏物发挥作用，并作为乙酰胆碱受体聚集基因rapsyn的激活剂。与其他BTB/POZ蛋白（例如Bcl-6、PLZF、HIC-1）类似，内源性Kaiso主要定位于哺乳动物细胞的细胞核。然而，迄今为止，包括Kaiso在内的大多数POZ转录因子的核输入机制仍然未知。在这里，我们报告的高度基本的核定位信号（NLS）在Kaiso的识别和表征。该NLS的功能性通过其将异源半乳糖苷酶/绿色荧光蛋白融合蛋白靶向细胞核的能力来验证。在全长Kaiso的NLS中，一个带正电荷的赖氨酸突变为丙氨酸，显著抑制了其在各种细胞类型中的核定位。此外，野生型Kaiso，而不是NLS缺陷型Kaiso，在体外和体内直接与核输入受体Importin-alpha 2相互作用。最后，使用序列特异性Kaiso结合位点与荧光素酶融合作为报告基因的最小启动子测定表明，所鉴定的NLS对于Kaiso介导的转录抑制至关重要。因此，Kaiso NLS的鉴定阐明了Kaiso易位到细胞核以调节在细胞生长和发育中具有不同作用的基因的转录的机制。
Kaiso is a BTB/POZ transcription factor that functions in vitro as a transcriptional repressor of the matrix metalloproteinase gene matrilysin and the non-canonical Wnt signaling gene Wnt-11, and as an activator of the acetylcholine-receptor-clustering gene rapsyn. Similar to other BTB/POZ proteins (e.g. Bcl-6, PLZF, HIC-1), endogenous Kaiso localizes predominantly to the nuclei of mammalian cells. To date, however, the mechanism of nuclear import for most POZ transcription factors, including Kaiso, remain unknown. Here, we report the identification and characterization of a highly basic nuclear localization signal (NLS) in Kaiso. The functionality of this NLS was verified by its ability to target a heterologous galactosidase/green-fluorescent-protein fusion protein to nuclei. The mutation of one positively charged lysine to alanine in the NLS of full-length Kaiso significantly inhibited its nuclear localization in various cell types. In addition, wild-type Kaiso, but not NLS-defective Kaiso, interacted directly with the nuclear import receptor Importin-alpha2 both in vitro and in vivo. Finally, minimal promoter assays using a sequence-specific Kaiso-binding-site fusion with luciferase as reporter demonstrated that the identified NLS was crucial for Kaiso-mediated transcriptional repression. The identification of a Kaiso NLS thus clarifies the mechanism by which Kaiso translocates to the nucleus to regulate transcription of genes with diverse roles in cell growth and development.