Nonmuscle myosin promotes cytoplasmic localization of PBX
Nonmuscle myosin promotes cytoplasmic localization of PBX
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DOI：
10.1128/mcb.23.10.3636-3645.2003
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发表时间：
2003-05-01
影响因子：
5.3
通讯作者：
Featherstone, M
中科院分区：
文献类型：
--
作者：
Huang, H;Paliouras, M;Featherstone, M
在缺乏MEIS家族蛋白的情况下，已知有两种机制将同源结构域（HD）转录因子的PBX家族限制在细胞质中。首先，PBX通过CRM 1依赖性途径从细胞核主动输出。第二，核定位信号（NLS）内的PBX HD被掩盖的分子内接触。在一个屏幕，以确定额外的蛋白质指导PBX亚细胞定位，我们确定了一个片段的小鼠非肌肉肌球蛋白II重链B（NMHC B）。免疫共沉淀证实了NMHCB与PBX的相互作用，免疫荧光染色显示NMHCB与细胞质PBX在小鼠胚胎远端肢芽中共定位。PBX中的相互作用域映射到保守的PBC-B区域，该区域具有潜在的卷曲螺旋结构。为了支持细胞质保留功能，NMHCB片段与MEIS 1A竞争将PBX和苍蝇PBX同源物EXD重定向至哺乳动物和昆虫细胞的细胞质。有趣的是，MEIS 1A在NMHCB片段存在下也定位于细胞质。这些活动在很大程度上与核出口无关。我们进一步表明，EXD的亚细胞定位是失调的果蝇拉链突变体是耗尽非肌肉肌球蛋白重链。这项研究揭示了一种新的和进化上保守的机制，控制PBX和EXD蛋白的亚细胞分布。
In the absence of MEIS family proteins, two mechanisms are known to restrict the PBX family of homeodomain (HD) transcription factors to the cytoplasm. First, PBX is actively exported from the nucleus via a CRM1-dependent pathway. Second, nuclear localization signals (NLSs) within the PBX HD are masked by intramolecular contacts. In a screen to identify additional proteins directing PBX subcellular localization, we identified a fragment of murine nonmuscle myosin II heavy chain B (NMHCB). The interaction of NMHCB with PBX was verified by coimmunoprecipitation, and immunofluorescence staining revealed colocalization of NMHCB with cytoplasmic PBX in the mouse embryo distal limb bud. The interaction domain in PBX mapped to a conserved PBC-B region harboring a potential coiled-coil structure. In support of the cytoplasmic retention function, the NMHCB fragment competes with MEIS1A to redirect PBX, and the fly PBX homologue EXD, to the cytoplasm of mammalian and insect cells. Interestingly, MEIS1A also localizes to the cytoplasm in the presence of the NMHCB fragment. These activities are largely independent of nuclear export. We show further that the subcellular localization of EXD is deregulated in Drosophila zipper mutants that are depleted of nonmuscle myosin heavy chain. This study reveals a novel and evolutionarily conserved mechanism controlling the subcellular distribution of PBX and EXD proteins.