Błaszczyk Leszek, Dutkiewicz Mariola, Ciesiołka Jerzy
Institute of Bioorganic Chemistry, Polish Academy of Sciences, 12/14 Noskowskiego St., 61-704 Poznań, Poland.
Postepy Biochem. 2007;53(4):400-12.
All eukaryotic mRNA molecules have a cap structure at the 5' ends which plays a crucial role in the scanning model of their translation initiation. In an alternative way of translation, the active ribosome is formed in a cap-independent mode due to the presence of IRES, internal ribosome entry site, in the 5' untranslated region of certain mRNAs. This region folds into a distinct secondary and tertiary structure, which binds the 40S ribosomal subunit and some protein factors, and subsequently forms the initiation complex and the translationally active 80S ribosome. This enables the synthesis of specific proteins under the conditions when cap-dependent translation is inhibited or strongly reduced. The cap-independent mode of translation initiation concerns proteins that play very important roles during cell cycle, apoptosis, response to stress stimuli and cancer development.
所有真核生物的mRNA分子在5'端都有一个帽结构，该结构在其翻译起始的扫描模型中起着关键作用。在另一种翻译方式中，由于某些mRNA的5'非翻译区存在内部核糖体进入位点（IRES），活性核糖体以不依赖帽的方式形成。该区域折叠成独特的二级和三级结构，与40S核糖体亚基和一些蛋白质因子结合，随后形成起始复合物和具有翻译活性的80S核糖体。这使得在帽依赖性翻译受到抑制或大幅减少的条件下能够合成特定蛋白质。不依赖帽的翻译起始模式涉及在细胞周期、细胞凋亡、应激刺激反应和癌症发展过程中发挥非常重要作用的蛋白质。
