2Omodifications

2O modifications, often referred to as 2′-O modifications, describe chemical substitutions at the 2′ oxygen position of the ribose sugar in nucleic acids. The most common example is 2′-O-methylation (2′-O-Me), but the term can also encompass a broader set of 2′-O substituents introduced by cellular enzymes or synthetic chemistry, such as 2′-O-allyl or 2′-O-ethyl groups. These modifications influence sugar pucker and backbone conformation, affecting RNA stability and interactions with proteins and other nucleic acids.

In biology, 2′-O modifications are widespread in RNA, particularly in ribosomal RNA, transfer RNA, and small nuclear RNAs across eukaryotes and archaea. Their installation is typically guided by small nucleolar ribonucleoproteins (snoRNPs) and dedicated methyltransferases, often using S-adenosylmethionine as the methyl donor. The distribution and abundance of 2′-O modifications can vary by organism, tissue type, developmental stage, and cellular conditions.

Detection and mapping of 2′-O modifications have been advanced by high-throughput sequencing and mass spectrometry. Methods such as RiboMeth-seq and related approaches infer 2′-O-Me sites from protection patterns against chemical or enzymatic treatments, or from direct mass spectral evidence, enabling cell- and tissue-specific profiling.

Biological significance of 2′-O modifications includes enhanced RNA stability against nucleases, altered RNA folding and base pairing, and modified RNA–protein interactions. They can influence ribosome function and translation fidelity. In therapeutic contexts, 2′-O modifications are commonly employed in antisense oligonucleotides and small interfering RNAs to improve stability, affinity, and resistance to degradation, while preserving or modulating biological activity.