Locked vs. unlocked nucleic acids (LNA vs. UNA): contrasting structures work towards common therapeutic goals

Abstract

Oligonucleotide chemistry has been developed greatly over the past three decades, with many advances in increasing nuclease resistance, enhancing duplex stability and assisting with cellular uptake. Locked nucleic acid (LNA) is a structurally rigid modification that increases the binding affinity of a modified-oligonucleotide. In contrast, unlocked nucleic acid (UNA) is a highly flexible modification, which can be used to modulate duplex characteristics. In this tutorial review, we will compare the synthetic routes to both of these modifications, contrast the structural features, examine the hybridization properties of LNA and UNA modified duplexes, and discuss how they have been applied within biotechnology and drug research. LNA has found widespread use in antisense oligonucleotide technology, where it can stabilize interactions with target RNA and protect from cellular nucleases. The newly emerging field of siRNAs has made use of LNA and, recently, also UNA. These modifications are able to increase double-stranded RNA stability in serum and decrease off-target effects seen with conventional siRNAs. LNA and UNA are also emerging as versatile modifications for aptamers. Their application to known aptamer structures has opened up the possibility of future selection of LNA-modified aptamers. Each of these oligonucleotide technologies has the potential to become a new type of therapy to treat a wide variety of diseases, and LNA and UNA will no doubt play a part in future developments of therapeutic and diagnostic oligonucleotides.

Splice-correcting oligonucleotides restore BTK function in X-linked agammaglobulinemia model

“…The amino-glycyl modification adds a glycyl residue to the N2′ position of 2′-amino-LNA, thereby providing a positive charge (51). UNA is known to decrease the Tm and destabilize the duplex, which potentially could increase target specificity if appropriately designed (52). ZEN is a naphthyl-azo modifier; when placed at or near both ends of a 2′OMe ON, it increases Tm and enhances the stability against endo-and exonucleases (37).…”

Mismatch discrimination in fluorescent in situ hybridization using different types of nucleic acids

“…However, it has been shown that for DNA sequences, this discrimination is often difficult to achieve (Kubota et al 2006). More recently, other types of synthetic nucleic acids such as peptide nucleic acid (PNA) and locked nucleic acids (LNA) have been used in FISH with very promising results (Guimaraes et al 2007;Mook et al 2007;Tavares et al 2008;Campbell and Wengel 2011;Almeida et al 2013;Cerqueira et al 2013). To understand the specificity of these novel molecules towards DNA and RNA, several thermal dissociation studies have been conducted to analyze the effects of mismatches on duplex stability (Owczarzy et al 2011;Yan et al 2012;Matsumoto et al 2013).…”

Probing the Key Binding Sequence and Improvement of the Stability of a β‐Bungarotoxin‐binding Aptamer in Snake Venom

“…LNAs, which are sugar modified nucleic acid analogues containing a methylene linkage between the 2 0 oxygen and the 4 0 carbon of the ribose ring (Figure 2), display unprecedented hybridization affinity toward complementary DNA (or RNA), enhanced duplex thermal stability, and increased resistance to degradation by nucleases. [29][30][31] As the S2 duplex did not directly participate in binding but was essential for the stabilization of the overall aptamer structure, we introduced LNA modifications in S2, aiming at improving stem stabilization and nuclease resistance while maintaining its binding affinity to the target. When the two distal base pairs of the aptamer βB-1.11 were replaced by LNAs (βB-1.11L1, Table S2), the Δr reached 0.0214 in competitive displacement assay whereas that of βB-1.11 was 0.0195 ( Figure S2), which indicated that the binding affinity of βB-1.11L1 was increased compared with that of βB-1.11.…”