14‐3‐3 suppresses the nuclear localization of threonine 157‐phosphorylated p27Kip1
14‐3‐3 suppresses the nuclear localization of threonine 157‐phosphorylated p27Kip1
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DOI：
10.1038/sj.emboj.7600198
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发表时间：
2004-05
期刊：
影响因子：
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通讯作者：
T. Sekimoto;M. Fukumoto;Y. Yoneda
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文献类型：
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作者：
T. Sekimoto;M. Fukumoto;Y. Yoneda
CDK抑制剂p27Kip1(P27)迁移到细胞核，在那里它控制细胞周期蛋白-CDK复合体的活动，以促进细胞周期的正常进行。我们在这里报道了经典的二元型碱性氨基酸簇和p27 C-末端区域的两个下游氨基酸作为其全面核输入活性的核定位信号(NLS)。Anin体外转运实验表明，Importinα3和α5，而不是α1，将p27与Importinβ一起转运到细胞核中。已知Akt使p27的Thr157磷酸化，从而降低了p27的核进口活性。通过下拉实验，14-3-3被鉴定为Thr157磷酸化的p27NLS结合蛋白。虽然Importinα5与Thr157磷酸化的p27NLS结合，但14-3-3与Importinα5竞争结合。因此，14-3-3从Importinα结合中隔离了磷酸化的p27NLS，导致了NLS磷酸化的p27的细胞质定位。这些发现表明，14-3-3抑制了依赖α/β的Thr157磷酸化p27的核定位，暗示了Akt激活的癌细胞的细胞周期紊乱。
p27Kip1(p27), a CDK inhibitor, migrates into the nucleus, where it controls cyclin–CDK complex activity for proper cell cycle progression. We report here that the classical bipartite‐type basic amino‐acid cluster and the two downstream amino acids of the C‐terminal region of p27 function as a nuclear localization signal (NLS) for its full nuclear import activity. Importin α3 and α5, but not α1, transported p27 into the nucleus in conjunction with importin β, as evidenced by anin vitrotransport assay. It is known that Akt phosphorylates Thr 157 of p27 and this reduces the nuclear import activity of p27. Using a pull‐down experiment, 14‐3‐3 was identified as the Thr157‐phosphorylated p27NLS‐binding protein. Although importin α5 bound to Thr157‐phosphorylated p27NLS, 14‐3‐3 competed with importin α5 for binding to it. Thus, 14‐3‐3 sequestered phosphorylated p27NLS from importin α binding, resulting in cytoplasmic localization of NLS‐phosphorylated p27. These findings indicate that 14‐3‐3 suppresses importin α/β‐dependent nuclear localization of Thr157‐phosphorylated p27, suggesting implications for cell cycle disorder in Akt‐activated cancer cells.