Interactions between short and long noncoding RNAs

It is now evident that noncoding RNAs play key roles in regulatory networks determining cell fate and behavior, in a myriad of different conditions, and across all species. Among these noncoding RNAs are short RNAs, such as MicroRNAs, snoRNAs, and Piwi‐interacting RNAs, and the functions of those are relatively well understood. Other noncoding RNAs are longer, and their modes of action and functions are also increasingly explored and deciphered. Short RNAs and long noncoding RNAs (lncRNAs) interact with each other with reciprocal consequences for their fates and functions. LncRNAs serve as precursors for many types of small RNAs and, therefore, the pathways for small RNA biogenesis can impinge upon the fate of lncRNAs. In addition, lncRNA expression can be repressed by small RNAs, and lncRNAs can affect small RNA activity and abundance through competition for binding or by triggering small RNA degradation.

As miRNAs and related small RNAs are already known to act in virtually every biological process in mammalian cells, and the spread of lncRNA influence is also increasing, it is likely that we will also see a dramatic increase in the known interactions between members of these two RNA classes. As lncRNAs are in general very similar in their structure and modifications to mRNAs, the modes and outcomes of their interactions with small RNAs also resemble those already seen with mRNAs, and indeed, none of the examples presented here, be it TDMD or cleavage by piRNAs appear to be unique to lncRNAs. As mentioned above, lncRNAs and mRNAs differ in their average abundance, stability, and localization, and these properties may affect the prevalence of their interactions with small RNAs, but it is important to keep in mind that there are thousands of lncRNAs that closely resemble mRNAs in each of those properties. Thus, the small‐long RNA network, that is just now beginning to be uncovered, is expected to remain a vibrant and fertile ground for future discoveries, and potentially even therapeutic interventions in a wide array of contexts.