Mechanisms directing the nuclear localization of the CtBP family proteins
Mechanisms directing the nuclear localization of the CtBP family proteins
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DOI：
10.1128/mcb.02402-05
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发表时间：
2006-07-01
影响因子：
5.3
通讯作者：
Crossley, Merlin
中科院分区：
文献类型：
--
作者：
Verger, Alexis;Quinlan, Kate G. R.;Crossley, Merlin
C-末端结合蛋白（CtBP）家族包括四种蛋白质（CtBP 1 [CtBP 1-L]、CtBP 3/BARS [CtBP 1-S]、CtBP 2和RIBEYE），它们参与转录抑制和细胞内运输。然而，不同的CtBP蛋白靶向不同的亚细胞区域的精确机制仍然未知。在这里，我们报告说，核进口的各种CtBP蛋白和剪接异构体的差异调节。我们发现，CtBP 2包含一个独特的核定位信号（NLS）位于其N-末端区域，这有助于其核积累。使用异核体分析，我们表明，CtBP 2是能够穿梭于细胞的细胞核和细胞质之间。此外，CtBP 2可以与CtBP 1-L和CtBP 1-S异源二聚化并将它们定向到细胞核。这种效应强烈依赖于CtBP 2 NLS。结合CtBP蛋白的含有PXDLS基序的转录因子，如BKLF，也可以将它们引导到细胞核。我们还报告了CtBP 2，CtBP 2-S，缺乏N-末端NLS和定位于细胞质的剪接异构体的鉴定。最后，我们表明，突变的CtBP NADH结合位点损害的能力的蛋白质二聚化，并与BKLF。这减少了CtBP 1的核积累。我们的研究结果表明，CtBP蛋白的核定位的影响CtBP 2 NLS的模型，通过结合到PXDLS基序伴侣蛋白，并通过对CtBP二聚化的NADH的效果。
The C-terminal binding protein (CtBP) family includes four proteins (CtBP1 [CtBP1-L], CtBP3/BARS [CtBP1-S], CtBP2, and RIBEYE) which are implicated both in transcriptional repression and in intracellular trafficking. However, the precise mechanisms by which different CtBP proteins are targeted to different subcellular regions remains unknown. Here, we report that the nuclear import of the various CtBP proteins and splice isoforms is differentially regulated. We show that CtBP2 contains a unique nuclear localization signal (NLS) located within its N-terminal region, which contributes to its nuclear accumulation. Using heterokaryon assays, we show that CtBP2 is capable of shuttling between the nucleus and cytoplasm of the cell. Moreover, CtBP2 can heterodimerize with CtBP1-L and CtBP1-S and direct them to the nucleus. This effect strongly depends on the CtBP2 NLS. PXDLS motif-containing transcription factors, such as BKLF, that bind CtBP proteins can also direct them to the nucleus. We also report the identification of a splice isoform of CtBP2, CtBP2-S, that lacks the N-terminal NLS and localizes to the cytoplasm. Finally, we show that mutation of the CtBP NADH binding site impairs the ability of the proteins to dimerize and to associate with BKLF. This reduces the nuclear accumulation of CtBP1. Our results suggest a model in which the nuclear localization of CtBP proteins is influenced by the CtBP2 NLS, by binding to PXDLS motif partner proteins, and through the effect of NADH on CtBP dimerization.