Male-specific splicing of the silkworm Imp gene is maintained by an autoregulatory mechanism.
Sexual differentiation in the silkworm Bombyx mori is controlled by sex-specific splicing of Bmdsx, in which exons 3 and 4 are skipped in males. B. mori insulin-like growth factor II mRNA-binding protein (Imp) is a factor involved in the male-specific splicing of Bmdsx. In this study, we found that the male-specific Imp mRNA is formed as a result of the inclusion of exon 8 and the promoter-distal poly(A) site choice, whereas non-sex-specific polyadenylation occurs at the promoter-proximal poly(A) site downstream of exon 7. Recent studies revealed that Drosophila Sxl, tra in several dipteran and hymenopteran insects, and fem in Apis mellifera, play a central role in sex determination and maintain their productive mode of expression via an autoregulatory function. To determine whether Imp protein is required for the maintenance of the male-specific splicing of its own pre-mRNA, we knocked down endogenous Imp in male cells and assessed the male-specific splicing of an exogenous Imp minigene. Knockdown of endogenous Imp inhibited the male-specific splicing of the Imp minigene transcript. In contrast, overexpression of Imp in female cells induced the male-specific splicing of the Imp minigene transcript. Moreover, deletion of adenine-rich (A-rich) sequences located downstream of the proximal poly(A) site repressed the male-specific splicing of the Imp minigene transcript. Finally, gel shift analysis demonstrated that Imp binds to the A-rich sequences. These data suggest that Imp binds to the A-rich sequences in its own pre-mRNA to induce the male-specific splicing of its pre-mRNA.
Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8562, Japan. Electronic address: gakyo@k.u-tokyo.ac.jp.
Masataka G
MG
Suzuki
Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8562, Japan. Electronic address: 126327@ib.k.u-tokyo.ac.jp.
Sayaka
S
Kobayashi
Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8562, Japan. Electronic address: aokif@k.u-tokyo.ac.jp.
Fugaku
F
Aoki
D000225:Adenine / Q000378:metabolism; D000818:Animals; D012831:Bombyx / Q000235:genetics* / Q000254:growth & development; D004268:DNA-Binding Proteins / Q000235:genetics*; D005091:Exons; D005260:Female; D055785:Gene Knockdown Techniques; D019476:Insect Proteins / Q000235:genetics*; D008297:Male; D012326:RNA Splicing / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D012727:Sex Characteristics; D019849:Sex Determination Processes
C442431:Bmdsx protein, Bombyx mori; D004268:DNA-Binding Proteins; D019476:Insect Proteins; D012333:RNA, Messenger; D000225:Adenine
Alternative splicing; Bombyx mori; Doublesex; Insulin-like growth factor II mRNA-binding protein; Sex determination