In higher eukaryotic cells, long non-protein-coding RNAs (lncRNAs) have been implicated in a wide array of cellular functions. Cellor tissue-specific expression of lncRNA genes encoded in the mammalian genome is thought to contribute to the complex gene networks needed to regulate cellular function. Here, we have identified a novel species of polypurine triplet repeat-rich lncRNAs, designated as GAA repeat-containing RNAs (GRC-RNAs), that localize to numerous punctate foci in the mammalian

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... phase nuclei. GRC-RNAs consist of a heterogeneous population of RNAs, ranging in size from ~1.5 kb to ~4 kb and localize to subnuclear domains, several of which associate with GAA.TTC-repeat-containing genomic regions. GRC-RNAs are components of the nuclear matrix and interact with various nuclear matrix-associated proteins. In mitotic cells, GRC-RNAs form distinct cytoplasmic foci and, in telophase and G1 cells, localize to the midbody, a structure involved in accurate cell division. Differentiation of tissue culture cells leads to a decrease in the number of GRC-RNA nuclear foci, albeit with an increase in size as compared with proliferating cells. Conversely, the number of GRC-RNA foci increases during cellular transformation. We propose that nuclear GRC-RNAs represent a novel family of mammalian lncRNAs that might play crucial roles in the cell nucleus. Journal of Cell Science 32 P-labeled (TTC) 15 probe from total RNA revealed that GRC-RNAs represent heterogeneous transcripts. Actin RNA was used as a loading control. (D)Northern blot using a 32 P-labeled (TTC) 15 probe in nuclear and cytoplasmic RNA fractions from EpH4 cells revealed nuclear enrichment of GRC-RNA. MALAT1 and lysine tRNA were used as markers for nuclear and cytoplasmic RNA fractionation, respectively. Journal of Cell Science Supplementary material available online at