Architectural RNAs (arcRNAs): A class of long noncoding RNAs that function as the scaffold of nuclear bodies.

Mammalian transcriptome analyses elucidated the presence of thousands of unannotated long noncoding RNAs (lncRNAs) with distinct transcriptional units. Molecular characterization and functional classification of these lncRNAs are important challenges in the next decade. A subset of these lncRNAs is the core of nuclear bodies, which are the sites of the biogenesis, maturation, storage, and sequestration of specific RNAs, proteins, and ribonucleoprotein complexes. Here, we define a class of lncRNAs termed architectural RNAs (arcRNAs) that function as the essential scaffold or platform of nuclear bodies. Presently, five lncRNAs from mammals, insects, and yeast are classified as arcRNAs. These arcRNAs are temporarily upregulated upon specific cellular stresses, in developmental stages, or in various disease conditions, and sequestrate specific regulatory proteins, thereby changing gene expression patterns. In this review, we introduce common aspects of these arcRNAs and discuss why RNA is used as the architectural component of nuclear bodies. This article is part of a Special Issue entitled: Clues to long noncoding RNA taxonomy1, edited by Dr. Tetsuro Hirose and Dr. Shinichi Nakagawa.