Effects of RNAi-mediated knockdown of histone methyltransferases on the sex-specific mRNA expression of Imp in the silkworm Bombyx mori.
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.
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. gakyo@k.u-tokyo.ac.jp.
Masataka G
MG
Suzuki
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. itofami@f6.dion.ne.jp.
Haruka
H
Ito
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. aokif@k.u-tokyo.ac.jp.
Fugaku
F
Aoki
D017398:Alternative Splicing; D000818:Animals; D012831:Bombyx / Q000201:enzymology* / Q000254:growth & development; D005260:Female; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008745:Methylation; D010063:Ovum / Q000378:metabolism; D063151:Polycomb Repressive Complex 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D012319:RNA Polymerase II / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism
D006657:Histones; D019476:Insect Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; D063151:Polycomb Repressive Complex 2; D012319:RNA Polymerase II