Cytotopic localization by long noncoding RNAs

Abstract

Cells are highly organized structures. In addition to membrane delimited organelles, proteins and RNAs can organize themselves into specific domains. Some examples include stress granules and subnuclear bodies. This level of organization is essential for the correct execution of multiple processes in the cell, ranging from cell signaling to assembly of structures such as the ribosomes. Here we will review evidence that noncoding RNAs play a critical role in the establishment and regulation of these domains. The unique abilities of RNA to mark the genome in a gene-specific and condition-specific manner and to serve as tethers nominate them as ideal molecular address codes.

Figure 1

(a) Transcription of the lncRNA NEAT1 leads to the accumulation of protein components at the site of transcription, and the formation of the Paraspeckle. (b) Cellular stress leads to the expression of IGSRNA, resulting in the retention at the nucleolus of proteins that would otherwise diffuse through the nucleoplasm. (c) During vegetative growth, meiotic mRNAs are targeted by for silencing by the protein Mmi1, which promotes RNA degradation and formation of facultative heterochromatic islands. Upon entry in meiosis, Mmi1 is recruited to the Mei2 dot, allowing for the expression of meiotic mRNAs. (d) The Pc2 complex is differentially methylated depending on the nutritional state of the cell. Depending on the state of methylation, Pc2 interacts with different lncRNA, leading to the presence of genes bound by Pc2 in different nuclear domains.