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Structural insights reveal the specific recognition of meiRNA by the Mei2 protein
Siyuan Shen1,2,† , Yanze Jian1,2,† , Zhaokui Cai3 , Fudong Li1,2 , Mengqi Lv1,2 , Yongrui Liu1,2 , Jihui Wu1,2 , Chuanhai Fu1,2,* , Yunyu Shi1,2,*
1School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230026, China
2MOE key Laboratory for Cellular Dynamics, University of Science & Technology of China, Hefei 230026, China
3Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
These authors contributed equally to this work.
*Correspondence to:Chuanhai Fu , Yunyu Shi ,
J Mol Cell Biol, Volume 14, Issue 5, May 2022, mjac029,
Keyword: Mei2, meiRNA, meiosis, RNA-binding protein, crystallography

In the fission yeast Schizosaccharomyces pombe, Mei2, an RNA-binding protein essential for entry into meiosis, regulates meiosis initiation. Mei2 binds to a specific non-coding RNA species, meiRNA, and accumulates at the sme2 gene locus, which encodes meiRNA. Previous research has shown that the Mei2 C-terminal RNA recognition motif (RRM3) physically interacts with the meiRNA 5′ region in vitro and stimulates meiosis in vivo. However, the underlying mechanisms still remain elusive. We first employed an in vitro crosslinking and immunoprecipitation sequencing (CLIP–seq) assay and demonstrated a preference for U-rich motifs of meiRNA by Mei2 RRM3. We then solved the crystal structures of Mei2 RRM3 in the apo form and complex with an 8mer RNA fragment, derived from meiRNA, as detected by in vitro CLIP–seq. These results provide structural insights into the Mei2 RRM3–meiRNA complex and reveal that Mei2 RRM3 binds specifically to the UUC(U) sequence. Furthermore, a structure-based Mei2 mutation, Mei2F644A causes defective karyogamy, suggesting an essential role of the RNA-binding ability of Mei2 in regulating meiosis.