Page 311 Posters: DNA metabolism, chromatin, gene expression Poster 173
Functional analysis of meiRNA, a non-coding RNA species essential for meiosis in fission yeast
Yuichi Shichino
a,b
, Akira Yamashita
b
, Masayuki Yamamoto
a,b
a
Kazusa DNA Res. Inst., Japan
b
Dept. Biophys. Biochem., Schl. of Sci., Univ. Tokyo, Japan
Presented by: Shichino, Yuichi
The gene expression profile changes dramatically between mitosis and meiosis in fission yeast. In mitotic cells, the meiosis-inhibitor Mmi1 recognizes the DSR
sequence in meiosis-specific mRNAs and eliminates them selectively. Mmi1 is observed as multiple dots in the mitotic nucleus. During meiosis, the master
meiotic regulator Mei2 and its binding partner meiRNA, which is non-coding, form a dot structure at the meiRNA gene locus. The Mei2 dot tethers Mmi1 into
a single dot and inactivates it. Thus, the meiosis-specific gene expression profile is ensured. meiRNA is thought to support the formation of Mei2 dot, but the
function of meiRNA has not been fully understood. To address this problem, we performed functional analysis of meiRNA, which plays an important role in the
regulation of meiotic progression.
In the original analysis of meiRNA, the major transcript was thought to be about 0.5 kb in length. However, we realized that the deduced downstream region of
the gene carries numerous hexanucleotide motifs that constitute DSR. This led us to re-investigate the role of meiRNA in the mRNA degradation system involving
Mmi1. In the mmi1-defective strain, the level of meiRNA expression increased and about 1.2 kb-long transcripts containing a number of DSR motifs called
meiRNA-L were detected in addition to the 0.5 kb-long transcripts called meiRNA-S. We then tried to dissect the functional domain of meiRNA-L. We
found that the γ’ region of meiRNA-L possessed the ability to bind to Mmi1, to promote meiosis, and to generate a dot. In contrast, Mei2 physically interacted
with the 5’ region of meiRNA-L. Moreover, overexpression of meiRNA-L in mitotic cells increased the number of cells containing a converged Mmi1 dot.
Taken together, these results suggest that meiRNA-L tethers Mmi1 and downregulates its function via the γ’ region, which abounds in the DSR motifs.
Page 312 Posters: DNA metabolism, chromatin, gene expression Poster 174
