Language：English   Publisher：Bioorganic and Medicinal Chemistry Letters  

The medicinal applications of siRNAs have been intensively examined but are still hindered by their low molecular stability under biological conditions and off-target effects, etc. The introduction of chemical modifications to the nucleoside is a promising strategy for solving these limitations. Herein, we describe the development of a new uridine analog, U*, that has a (methylthiomethoxy)methoxy group at the 2′ position. The phosphoramidite reagent corresponding to U* was easily synthesized and the RNA oligonucleotides containing U* were stably prepared using a standard protocol for oligonucleotide synthesis. The introduction of U* into the siRNA resulted in positive or negative effects on the targeted gene silencing in a position-dependent manner, and the positive effects were attributed to the improved stability under biological conditions. The thermodynamic analysis of the U*-modified RNAs revealed a slight destabilization of the dsRNA, based depending on which U was strategically utilized to restrain the off-target effects of the siRNA. This study describes a rare example of nucleoside analogs with a large substitution at the 2′-position in the context of an siRNA application and is informative for the development of other analogs to further improve the molecular properties of siRNAs for medicinal applications.

DOI： 10.1016/j.bmcl.2022.128939

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Language：English   Publisher：ACS Chemical Biology  

Site-specific chemical modification of mRNA can improve its translational efficiency and stability. For this purpose, it is desirable to develop a complete chemical synthesis method for chemically modified mRNA. The key is a chemical reaction that introduces a cap structure into the chemically synthesized RNA. In this study, we developed a fast and quantitative chemical capping reaction between 5′-phosphorylated RNA and N7-methylated GDP imidazolide in the presence of 1-methylimidazole in the organic solvent dimethyl sulfoxide. It enabled quantitative preparation of capping RNA within 3 h. We prepared chemically modified 107-nucleotide mRNAs, including N6-methyladenosine, insertion of non-nucleotide linkers, and 2′-O-methylated nucleotides at the 5′ end and evaluated their effects on translational activity in cultured HeLa cells. The results showed that mRNAs with non-nucleotide linkers in the untranslated regions were sufficiently tolerant to translation and that mRNAs with the Cap_2 structure had higher translational activity than those with the Cap_0 structure.

DOI： 10.1021/acschembio.1c00996

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Language：English  

DOI： 10.1002/cbic.202100413

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Language：Japanese  

DOI： 10.1002/cbic.202100312

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Language：Japanese   Publisher：The Pharmaceutical Society of Japan  

Currently, mRNA is used for vaccine therapy against COVID-19. However, the mRNA vaccine is urgently approved under a pandemic, there are still issues to be solved in terms of delivery method, quality/ purity, stability/ effect sustainability, protein synthesis efficiency, and so on. Research and development of mRNA drugs have been mainly focused on the development of delivery methods, and only biological methods are used for mRNA production. It is important to develop molecular design methods and synthetic methods hereafter. We focus on the translation mechanism of mRNA and propose a molecular design that can promote the translation by accelerate its rate-determining step. Based on experimental data, we will explain here the strategy for the molecule design that can improve the translation efficiency and stability of mRNA.

DOI： 10.14894/medchem.31.4_194

CiNii Research

Publisher：Angewandte Chemie - International Edition  

DOI： 10.1002/anie.202007111

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Publisher：Chemical Communications  

DOI： 10.1039/d0cc02140g

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Publisher：Nucleosides, Nucleotides and Nucleic Acids  

DOI： 10.1080/15257770.2019.1671593

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Publisher：Chemical Communications  

DOI： 10.1039/c9cc04872c

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Language：English   Publisher：The Pharmaceutical Society of Japan  

<p>Efficient methods for delivery of antisense DNA or small interfering RNA (siRNA) are highly needed. Cationic materials, which are conventionally used for anionic oligonucleotide delivery, have several drawbacks, including aggregate formation, cytotoxicity and a low endosome escape efficiency. In this report a bio-reactive mask (<i>i.e.</i>, disulfide unit) for cationic amino groups was introduced, and the mask was designed such that it was removed at the target cell surface. Insolubility and severe cellular toxicity caused by exposed cationic groups are avoided when using the mask. Moreover, the disulfide unit used to mask the cationic group enabled direct delivery of oligonucleotides to the cell cytosol. The molecular design reported is a promising approach for therapeutic applications.</p>

DOI： 10.1248/cpb.c19-00811

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CiNii Research

Publisher：Nucleosides, Nucleotides and Nucleic Acids  

DOI： 10.1080/15257770.2019.1641205

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Publisher：Angewandte Chemie - International Edition  

DOI： 10.1002/anie.201900993

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Publisher：ChemBioChem  

DOI： 10.1002/cbic.201800671

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Publisher：Methods in Molecular Biology  

DOI： 10.1007/978-1-4939-7562-4_15

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Publisher：Nucleic Acids Research  

DOI： 10.1093/nar/gkx459

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Publisher：The Biophysical Society of Japan General Incorporated Association  

<p>In an <i>E. coli</i> cell-free translation system, we found that a circular RNA containing an infinite open reading frame produced more translation product than its linear counterpart by two orders of magnitude, because a ribosome can work more effectively towards the elongation on circular RNA than it can on linear RNA. We then tested circular RNAs containing an infinite open reading frame could be translated in eukaryotic systems, in the absence of any particular element for internal ribosome entry, a poly-A tail, or a cap structure. We found that the circular RNAs also produced long peptides in eukaryotic translation systems, possibly owing to the rolling circle amplification mechanism.</p>

DOI： 10.2142/biophys.57.005