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Annexin A2 binds the internal ribosomal entry site of c-myc mRNA and regulates its translation
RNA Biology ( IF 4.1 ) Pub Date : 2021-08-04 , DOI: 10.1080/15476286.2021.1947648
Elin Strand 1, 2 , Hanne Hollås 1 , Siri Aastedatter Sakya 1, 3 , Sofya Romanyuk 1, 4 , Mikko E V Saraste 1, 5 , Ann Kari Grindheim 1 , Sudarshan S Patil 1 , Anni Vedeler 1
Affiliation  

ABSTRACT

The expression and localization of the oncoprotein c-Myc is highly regulated at the level of transcription, mRNA transport, translation, as well as stability of the protein. We previously showed that Annexin A2 (AnxA2) binds to a specific localization element in the 3ʹuntranslated region (UTR) of c-myc mRNA and is involved in its localization to the perinuclear region. In the present study, we demonstrate that AnxA2 binds in a Ca2+-dependent manner to the internal ribosomal entry site (IRES) containing two pseudo-knots in the 5´UTR of the c-myc mRNA. Here, we employ an in vitro rabbit reticulocyte lysate system with chimeric c-myc reporter mRNAs to demonstrate that binding of AnxA2 to the c-myc IRES modulates the expression of c-Myc. Notably, we show that low levels of AnxA2 appear to increase, while high levels of AnxA2 inhibits translation of the chimeric mRNA. However, when both the AnxA2-binding site and the ribosomal docking site in the c-myc IRES are deleted, AnxA2 has no effect on the translation of the reporter mRNA. Forskolin-treatment of PC12 cells results in upregulation of Ser25 phosphorylated AnxA2 expression while c-Myc expression is down-regulated. The effect of forskolin on c-Myc expression and the level of Ser25 phosphorylated AnxA2 was abolished in the presence of EGTA. These findings indicate that AnxA2 regulates both the transport and subsequent translation of the c-myc mRNA, possibly by silencing the mRNA during its transport. They also suggest that AnxA2 act as a switch to turn off the c-myc IRES activity in the presence of calcium.

Abbreviations: AnxA2, Annexin A2; β2--µglob, β2-microglobulin; cpm, counts per minute; hnRNP, heterogenous nuclear ribonucleoprotein; IRES, internal ribosomal entry site; ITAF, IRES trans-acting factor; MM, multiple myeloma; PABP, poly(A)-binding protein; PCBP, poly(rC) binding protein; PSF, PTB-associated splicing factor; PTB, polypyrimidine tract binding protein; RRL, rabbit reticulocyte lysate; UTR, untranslated region; YB, Y-box binding protein.



中文翻译:

膜联蛋白 A2 结合 c-myc mRNA 的内部核糖体进入位点并调节其翻译

摘要

癌蛋白 c-Myc 的表达和定位在转录、mRNA 转运、翻译以及蛋白质的稳定性水平上受到高度调节。我们之前表明,膜联蛋白 A2 (AnxA2) 与 c- myc mRNA的 3'非翻译区 (UTR) 中的特定定位元件结合,并参与其定位到核周区域。在本研究中,我们证明 AnxA2 以 Ca 2+依赖性方式与 c- myc mRNA 的 5'UTR 中包含两个假结的内部核糖体进入位点 (IRES) 结合。在这里,我们采用具有嵌合 c- myc报告基因的体外兔网织红细胞裂解物系统来证明 AnxA2 与 c- myc的结合。IRES 调节 c-Myc 的表达。值得注意的是,我们显示低水平的 AnxA2 似乎增加,而高水平的 AnxA2 抑制嵌合 mRNA 的翻译。然而,当 c- myc IRES 中的 AnxA2 结合位点和核糖体对接位点都被删除时,AnxA2 对报告 mRNA 的翻译没有影响。PC12 细胞的毛喉素处理导致 Ser25 磷酸化 AnxA2 表达上调,而 c-Myc 表达下调。福司可林对 c-Myc 表达和 Ser25 磷酸化 AnxA2 水平的影响在 EGTA 存在下被取消。这些发现表明 AnxA2 调节 c- myc的运输和随后的翻译。mRNA,可能是通过在其运输过程中使 mRNA 沉默。他们还建议 AnxA2 在钙存在的情况下充当关闭 c- myc IRES 活性的开关。

缩写:AnxA2,Annexin A2;β 2 --微球蛋白,β 2 -微球蛋白;cpm,每分钟计数;hnRNP,异质核核糖核蛋白;IRES,内部核糖体进入位点;ITAF、IRES反式作用因子;MM,多发性骨髓瘤;PABP,聚(A)结合蛋白;PCBP,聚(rC)结合蛋白;PSF,PTB 相关剪接因子;PTB,聚嘧啶束结合蛋白;RRL,兔网织红细胞裂解物;UTR,未翻译区;YB,Y-盒结合蛋白。

更新日期:2021-08-04
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