Protein ligands mediate the CRM1-dependent export of HuR in response to heat shock
Protein ligands mediate the CRM1-dependent export of HuR in response to heat shock
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DOI：
10.1017/s1355838201016089
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发表时间：
2001-09-01
期刊：
影响因子：
4.5
通讯作者：
Steitz, JA
中科院分区：
文献类型：
--
作者：
Gallouzi, IE;Brennan, CM;Steitz, JA
富含AU的元件（战神）位于许多哺乳动物早期反应基因的信使RNA（mRNA）的3'UTR中，促进mRNA的快速更新。HuR是一种含有RRM的RNA结合蛋白，与战神特异性相互作用，稳定这些mRNA。HuR主要是核质，但通过位于RRM 2和RRM 3之间的称为HNS的结构域在细胞核和细胞质之间穿梭。我们最近发现HuR与两种蛋白质配体pp 32和APRIL相互作用，这两种蛋白质配体也是穿梭蛋白，但依赖于CRM 1识别的内斯结构域进行输出。在这里，我们表明热休克通过蛋白质-蛋白质相互作用诱导HuR与pp 32和APRIL的结合增加，并且这些配体与HuR部分共定位在细胞质病灶中。HuR与hnRNP复合物的结合也增加，但通过RNA连接。CRM 1仅在热休克后与HuR共免疫沉淀，并且HuR的核输出对CRM 1的抑制剂来普霉素B变得敏感。热休克后的输出需要与结合pp 32和APRIL所必需的HuR（HNS和RRM 3）相同的结构域。原位杂交和免疫共沉淀实验表明，LMB治疗阻断热休克后hsp 70 mRNA的核输出和其与HuR的细胞质相互作用。总之，我们的研究结果表明，在热休克，HuR切换其出口途径，其配体pp 32和APRIL，其中涉及核输出因子CRM 1。HuR及其配体可能有助于热休克mRNA的核输出。
AU-rich elements (AREs) located in the 3' UTRs of the messenger RNAs (mRNAs) of many mammalian early response genes promote rapid mRNA turnover. HuR, an RRM-containing RNA-binding protein, specifically interacts with AREs, stabilizing these mRNAs. HuR is primarily nucleoplasmic, but shuttles between the nucleus and the cytoplasm via a domain called HNS located between RRM2 and RRM3. We recently showed that HuR interacts with two protein ligands, pp32 and APRIL, which are also shuttling proteins, but rely on NES domains recognized by CRM1 for export. Here we show that heat shock induces increased association of HuR with pp32 and APRIL through protein-protein interactions and that these ligands partially colocalize with HuR in cytoplasmic foci. HuR associations with the hnRNP complex also increase, but through RNA links. CRM1 coimmunoprecipitates with HuR only after heat shock, and nuclear export of HuR becomes sensitive to leptomycin B, an inhibitor of CRM1. Export after heat shock requires the same domains of HuR (HNS and RRM3) that are essential for binding pp32 and APRIL. In situ hybridization and coimmunoprecipitation experiments show that LMB treatment blocks both hsp70 mRNA nuclear export and its cytoplasmic interaction with HuR after heat shock. Together, our results argue that upon heat shock, HuR switches its export pathway to that of its ligands pp32 and APRIL, which involves the nuclear export factor CRM1. HuR and its ligands may be instrumental in the nuclear export of heat-shock mRNAs.