Meiotic long non-coding meiRNA accumulates as a dot at its genetic locus facilitated by Mmi1 and plays as a decoy to lure Mmi1.

Abstract

Long non-coding RNAs (lncRNAs) play key roles in the formation of nuclear bodies. In the fission yeast Schizosaccharomyces pombe, a lncRNA species termed meiRNA forms a nuclear dot structure at its own genetic locus, the sme2 locus, with its protein-binding partner Mei2. This dot structure, called Mei2 dot, promotes the progression of meiosis by suppressing Mmi1, a crucial factor involved in the selective elimination of meiosis-specific transcripts. The meiRNA itself is a target of Mmi1-mediated elimination and is supposed to function as a decoy to lure Mmi1. However, detailed mechanisms underlying the formation of Mei2 dot and inactivation of Mmi1 remain ambiguous. Here, we show that the localization of meiRNA, at its genetic locus sme2, depends on its association with Mmi1. We also demonstrate that one of the multiple Mmi1 foci in mitotic cells localizes to the sme2 locus. Furthermore, the overexpression of meiRNA promotes the accumulation of Mmi1 to the sme2 locus even in the absence of Mei2 and reduces the activity of Mmi1. These findings indicate that the retention of meiRNA at its genetic locus is facilitated by Mmi1, which then attracts scattered Mmi1 to inhibit its function.