Tuning Gene Expression by Hairpin Elements near the Start Codon of mRNA in Mammalian Cells^†

The hairpin element (HpE) near the start codon in the 5′ untranslated region (UTR) was developed to tune the mRNA translation in mammalian cells. The parameters of HpEs including thermodynamic stability, the content of guanine and cytosine, and distance between HpEs and the 5′ cap were investigated. These parameters influenced the mRNA expression level. In addition, the start codon and the upstream open reading frame sequestered within the structures of HpEs also reduced the translation initiation. In summary, this study shows that the simple engineering HpE structure can be efficiently adopted for gene expression regulation. The predictable controllability of this simple cloning strategy can potentially achieve precise gene expression regulation in different mammalian cell types.