1、mRNA的3’非编码区（3’UTR）有哪些和基因表达调控有关的结构，功能分别是什么？

（1）、MicroRNA response elements（MRE）、MicroRNA应答元件

（2）、AU-rich elements（ARE）、富含AU元件

（3）、Poly(A) tail、多聚腺苷酸

2、请解释什么叫做“Circularization ofthe mRNA transcript”？

答案：

The poly(A) tailcontains binding sites for poly(A) binding proteins (PABPs). These proteinscooperate with other factors to affect the export, stability, decay, andtranslation of an mRNA. PABPs bound to the poly(A) tail may also interact withproteins, such as translation initiation factors, that are bound to the 5' capof the mRNA. This interaction causes circularization of the transcript, whichsubsequently promotes translation initiation. Furthermore, it allows forefficient translation by causing recycling of ribosomes.