The Definition of RNA Age Related to RNA Sequence Changes

Ribonucleic acid (RNA) undergoes dynamic changes in its structure and function under various intracellular and extracellular conditions over time. However, there is a lack of research on the concept of the RNA age to describe its diverse fates. This study proposes a definition of RNA age to address this issue. RNA age was defined as a sequence of numbers wherein the elements in the sequence were the nucleotide ages of the ribonucleotide residues in the RNA. Mean nucleotide age was used to represent RNA age. This definition describes the temporal properties of RNAs that have undergone diverse life histories and reflects the dynamic state of each ribonucleotide residue, which can be expressed mathematically. Notably, events (including base insertions, base deletions, and base substitutions) are likely to cause RNA to become younger or older when using mean nucleotide ages to represent the RNA age. Although information, including the presence of added markers in RNA, chemical modification structure of the RNA, and the excision of introns in the mRNA in cells, may provide a basis for identifying RNA age, little is known about determining the RNA age of extracellular RNA in the wild. Nonetheless, we believe that RNA age has an important relationship with the diverse biological properties of RNA under intracellular and extracellular conditions. Therefore, our proposed definition of RNA age offers new perspectives for studying dynamic changes in RNA function, RNA aging, ancient RNA, environmental RNA, and the ages of other biomolecules.