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[Seminar Notification] Dr. Mihye Lee_04.28.2016
2016-04-21

1. Title : Regulation of Maternally Inherited RNAs

2. Speaker : Mihye Lee, Ph.D.

3. Affiliation : Institute of Basic Science and School of Biological Sciences, Seoul National University, Seoul, Republic of Korea

4. Date : 04. 28. 2016 16:00-17:00

5. Place : SIMS Main Building, Auditorium 109 (1F)

6. Abstract :

Early development depends heavily on accurate control of maternally inherited mRNAs because transcription is silenced from late stage oogenesis to the beginning of embryogenesis. Thus, maternal mRNAs are under extensive posttranscriptional regulation for their stability and translation. But, it remains unknown how maternal microRNAs are regulated during this beginning stage of life. Here, we found that maternal microRNAs are highly adenylated at their 3ends in mature oocytes and early embryos. Atailing (3end adenylation) of maternal microRNA is widely conserved in fly, sea urchin, and mouse. We identified Wispy, a noncanonical poly(A)  polymerases, as the enzyme responsible for microRNA adenylation in flies. Knockout of wispy abrogates adenylation and results in microRNA accumulation in eggs, whereas overexpression of Wispy increases adenylation and reduces microRNA levels in S2 cells. Wispy interacts with Ago1 through proteinprotein interaction, which may allow the effective and selective adenylation of microRNAs. Thus, adenylation may contribute to the learance of maternally deposited microRNAs during maternaltozygotic transition (MZT). In addition to Atailing of microRNA, we also discovered dynamic poly(A) tailing of mRNA in mature oocytes and early embryos. With newly developed method, TAILseq, we found that maternal mRNAs are polyadenylated mainly during late oogenesis, prior to fertilization, and further modulated upon egg activation. Wispy adenylates most maternal mRNAs with a few intriguing exceptions such as ribosomal protein transcripts. By comparing TAILseq data to ribosome profiling data, we further revealed a strong coupling between poly(A) tail length and translational efficiency during egg activation. Our data suggest that regulation of poly(A) tail in oocytes shapes the translational landscape of embryos, thereby directing the onset of animal development. From indepth tailing analysis of microRNAs and mRNAs in mature oocytes and early embryos, we provide mechanistic insights into the regulation of maternal RNAs by noncanonical poly(A) polymerase, and illustrate the importance of RNA tailing in development.