Preferential translation mediated by Hsp81-3 5′-UTR during heat shock involves ribosome entry at the 5′-end rather than an internal site in Arabidopsis suspension cells
Preferential translation mediated by Hsp81-3 5′-UTR during heat shock involves ribosome entry at the 5′-end rather than an internal site in Arabidopsis suspension cells
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DOI：
10.1263/jbb.105.39
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发表时间：
2008-01-01
影响因子：
2.8
通讯作者：
Kato, Ko
中科院分区：
文献类型：
--
作者：
Matsuura, Hideyuki;Shinmyo, Atsuhiko;Kato, Ko
在热休克应激条件下，大多数细胞中的大部分mRNAs发生翻译抑制，而编码热休克蛋白(HSPs)的mRNAs发生优先翻译。对于大多数HSP mRNAs来说，热休克细胞中的优先翻译是由其5‘-非翻译区(5’-UTRs)授予的。然而，在植物中，5‘-UTRs在热激过程中引导的优先翻译仍然是未知的。在此，我们发现拟南芥Hsp90家族基因Hsp81-3的信使核糖核酸继续与热休克的拟南芥悬浮培养细胞中的多聚体相关。通过瞬时表达分析发现，Hsp81-3 5‘-UTR有助于热休克拟南芥原生质体中封顶报告基因mRNAs的有效翻译。对Hsp81-3 5‘-非编码区的进一步鉴定表明，5’-非编码区的前半部分对于热休克原生质体的高效翻译是重要的。此外，Hsp81-3 5‘-UTR在正常和热休克原生质体中都能相对于看家基因的5’-UTR高度增强从无封顶报告基因mRNAs的翻译。在5‘-UTR5’端插入上游AUG，大大减少了Hsp81-3 5‘-UTR在有帽和无帽报告mRNA中的翻译，表明核糖体被招募到Hsp81-3 5’-UTR5‘端，无论温度和帽结构的存在与否。这些结果表明，Hsp81-3mRNA在热休克拟南芥细胞中的优先翻译涉及从5‘-UTR5’端的核糖体扫描，而不是核糖体进入内部部位。
Translational inhibition of most mRNAs and preferential translation of mRNAs coding heat shock proteins (Hsps) occur in most cells under heat shock stress. For most Hsp mRNAs, preferential translation in heat-shocked cells is conferred by their 5'-untranslated regions (5'-UTRs). However, the preferential translation directed by 5'-UTRs during heat shock remains mostly unknown in plants. Here, we found that the mRNA of Hsp81-3, which is an Arabidopsis Hsp90 family gene, continued to be associated with polysomes in heat-shocked Arabidopsis suspension-cultured cells. The Hsp81-3 5'-UTR was found to contribute to the efficient translation of capped reporter mRNAs in heat-shocked Arabidopsis protoplasts using a transient expression assay. Further characterization of the Hsp81-3 5'-UTR revealed that the anterior half of the 5'-UTR is important for the efficient translation in heat-shocked protoplasts. Moreover, the Hsp81-3 5'-UTR was highly capable of enhancing translation from uncapped reporter mRNAs relative to the 5'-UTR of a housekeeping gene in both normal and heat-shocked protoplasts. These Hsp81-3 5'-UTR-directed translations both in capped and uncapped reporter mRNAs were substantially reduced by the insertion of an upstream AUG at the 5'-end of the 5'-UTR, indicating that ribosomes are recruited to the 5'-end of the Hsp81-3 5'-UTR regardless of temperature and the presence or absence of the cap structure. These results suggest that the preferential translation of Hsp81-3 mRNA in heat-shocked Arabidopsis cells involves a ribosome scanning from the 5'-end of the 5'-UTR rather than ribosome entry to the internal site.