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Int. J. Mol. Sci. 2014, 15(4), 6772-6796; doi:10.3390/ijms15046772
Article

Effects of RNAi-Mediated Knockdown of Histone Methyltransferases on the Sex-Specific mRNA Expression of Imp in the Silkworm Bombyx mori

* ,
 and
Division of Biological Sciences, Department of Integrated Biosciences, Graduate School of Frontier Sciences, the University of Tokyo, 302 Bioscience-Bldg, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562, Japan
* Author to whom correspondence should be addressed.
Received: 19 February 2014 / Revised: 25 March 2014 / Accepted: 10 April 2014 / Published: 22 April 2014
(This article belongs to the Special Issue Pre-mRNA Splicing)
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Abstract

Sexual differentiation in Bombyx mori is controlled by sex-specific splicing of Bmdsx, which results in the omission of exons 3 and 4 in a male-specific manner. In B. mori, insulin-like growth factor II mRNA-binding protein (Imp) is a male-specific factor involved in male-specific splicing of Bmdsx. Male-specific Imp mRNA results from the male-specific inclusion of exon 8. To verify the link between histone methylation and alternative RNA processing in Imp, we examined the effects of RNAi-mediated knockdown of several histone methyltransferases on the sex-specific mRNA expression of Imp. As a result, male-specific expression of Imp mRNA was completely abolished when expression of the H3K79 methyltransferase DOT1L was repressed to <10% of that in control males. Chromatin immunoprecipitation-quantitative PCR analysis revealed a higher distribution of H3K79me2 in normal males than in normal females across Imp. RNA polymerase II (RNAP II) processivity assays indicated that RNAi knockdown of DOT1L in males caused a twofold decrease in RNAP II processivity compared to that in control males, with almost equivalent levels to those observed in normal females. Inhibition of RNAP II-mediated elongation in male cells repressed the male-specific splicing of Imp. Our data suggest the possibility that H3K79me2 accumulation along Imp is associated with the male-specific alternative processing of Imp mRNA that results from increased RNAP II processivity.
Keywords: alternative splicing; DOT1L; histone H3 methylation; sex determination alternative splicing; DOT1L; histone H3 methylation; sex determination
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).
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Suzuki, M.G.; Ito, H.; Aoki, F. Effects of RNAi-Mediated Knockdown of Histone Methyltransferases on the Sex-Specific mRNA Expression of Imp in the Silkworm Bombyx mori. Int. J. Mol. Sci. 2014, 15, 6772-6796.

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