A Juvenile Hormone-Transcription Factor Bmdimm-Fibroin H chain pathway is involved in the synthesis of silk protein in silkworm, Bombyx mori [Gene Regulation]

November 4th, 2014 by Zhao, X.-M., Liu, C., Jiang, L.-J., Li, Q.-Y., Zhou, M.-T., Cheng, T.-C., Mita, K., Xia, Q.-Y.

The genes responsible for silk biosynthesis are switched on and off at particular times in the silk glands of Bombyx mori. This switch appears to be under the control of endogenous and exogenous hormones. However, the molecular mechanisms by which silk protein synthesis is regulated by juvenile hormone (JH) are largely unknown. Here, we report a basic helix-loop-helix transcription factor (bHLH), Bmdimm, its silk gland-specific expression and its direct involvement in the regulation of fibroin H-chain (fib-H) by binding to an E-box (CAAATG) element of the fib-H gene promoter. Far-western blots, enzyme linked immunosorbent assays, and Co-Immunoprecipitation assays revealed that Bmdimm protein interacted with another bHLH transcription factor, Bmsage. Immunostaining revealed that Bmdimm and Bmsage proteins are colocalized in nuclei. Bmdimm expression was induced in larval silk glands in vivo, in silk glands cultured in vitro and in B. mori cell lines after treatment with a JH analog. The JH effect on Bmdimm was mediated by the JH-Met-Kr-h1 signaling pathway, and Bmdimm expression did not respond to JH by RNA interference with double-stranded BmKr-h1 RNA. These data suggests that the JH regulatory pathway, the transcription factor Bmdimm, and the targeted fib-H gene contribute to the synthesis of fibroin H-chain protein in B. mori.
  • Posted in Journal of Biological Chemistry, Publications
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