Abstract
Meiosis is one of the most dramatic differentiation programs accompanied by a striking change in gene expression profiles, whereas a number of meiosis-specific transcripts are expressed untimely in mitotic cells. The entry of meiosis will be blocked as the accumulation of meiosis-specific mRNAs during the mitotic cell in fission yeast Schizosaccharomyces pombe. A YTH domain containing protein Mmi1 was identified as a pivotal effector in a post-transcriptional event termed selective elimination of meiosis-specific mRNAs, Mmi1 can recognize and bind a class of meiosis-specific transcripts expressed inappropriately in mitotic cells, which contain a conservative motif called DSR as a mark to remove them in cooperation with nuclear exosomes. Here we report the 1.6 Å resolution crystal structure of the YTH domain of Mmi1 binds to high-affinity RNA targets r(A1U2U3A4A5A6C7A8) containing DSR core motif. Our structure observations, supported by site-directed mutations of key residues illustrate the mechanism for specific recognition of DSR-RNA by Mmi1. Moreover, different from other YTH domain family proteins, Mmi1 YTH domain has a distinctive function although it has a similar fold as other ones.
