RSC chemical biologyAug 29, 2025

Stability and protein binding of chemically modified poly(A) tails for use in living organisms

mRNA Technology Weekly Brief ↗PubMed ↗DOI ↗OA ↗

Updated Mar 18, 2026

Abstract

Chemical modifications of the poly(A) tail can enhance mRNA stability and translation efficiency.

Phosphorothioate (PS), 2'-O-methyl (2'-OMe), and 2'-methoxyethyl (2'-MOE) modifications provide resistance to the deadenylation enzyme .
Only the PS modification maintains the binding activity of the poly(A)-binding protein (), which is essential for translation.
The combination of 2'-F, 2'-OMe, and 2'-MOE modifications improves resistance to CAF1 and other nucleases.
Inserting a 12-nucleotide unmodified poly(A) sequence upstream of the modified poly(A) enhances both nuclease resistance and PABP binding.
The modified poly(A) formulation significantly increases protein expression in cultured cells and mouse skin for therapeutic mRNA.

Simplified

The poly(A) tail plays a crucial role in mRNA stability and translation efficiency. Chemical modification of the poly(A) tail is a promising approach for stabilizing mRNA against deadenylation. In this study, we investigated the effect of poly(A) chemical modifications using phosphorothioate (PS), 2'-fluoro (2'-F), 2'--methyl (2'-OMe), and 2'--methoxyethyl (2'-MOE) modifications. Notably, PS, 2'-OMe, and 2'-MOE modifications conferred resistance to , an enzyme responsible for deadenylation. Interestingly, only the PS modification retained the poly(A)-binding protein () binding activity, which is critical for translation, whereas 2'-F, 2'-OMe, and 2'-MOE modifications abolished this activity. Beyond the PS modification, the combination of 2'-F, 2'-OMe, and 2'-MOE modifications resulted in enhanced resistance to both CAF1 and other nucleases. Based on these results, a 12-nucleotide unmodified poly(A) sequence was inserted upstream of the modified poly(A) to confer both nuclease resistance and PABP-binding activity. Notably, the resulting poly(A) formulation significantly prolonged protein expression in cultured cells and mouse skin when applied to epidermal growth factor-encoding therapeutic mRNA. Collectively, this study presents a design concept for poly(A) chemical modifications to achieve durable protein expression from mRNA, offering a promising strategy for enhancing the function of mRNA-based therapeutics. O O

Key numbers

1.8×

Binding Affinity Increase

Affinity increase of for PS-modified poly(A) tail.

1 week

Protein Expression Duration

Duration of EGF protein expression from modified mRNA in mouse skin.

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Funding

Competing interests

AH, YK, IK, HY, KK, KS, HA, YS, JY, and HI are employees of Kyowa Kirin Co. Ltd.

PubMed

Stability and protein binding of chemically modified poly(A) tails for use in living organisms

Abstract

Key numbers

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Competing interests

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