title: Nuclear hormone receptor BmFTZ-F1 is involved in regulating the fibroin heavy chain gene in the silkworm, Bombyx mori.
abstract: The synthesis of silk protein is controlled by hormones. The expression of the nuclear hormone Bmftz-f1 in the posterior silk gland (PSG) is induced by 20-hydroxyecdysone in vivo and in vitro. However, whether Bmftz-f1 regulates silk protein expression is unknown.
  
  
  
  In our study, western blotting and quantitative polymerase chain reactions were conducted to detect the expression of FTZ-F1 in the PSG. Electrophoretic mobility shift, chromatin immunoprecipitation, far-western blotting, bimolecular fluorescence complementation, and dual luciferase reporter assays were performed to investigate the effect of FTZ-F1 on the fibH promoter.
  
  
  
  (1) The expression of the hormone receptor BmFTZ-F1 was opposite to that of fibH. It was highly expressed in the PSG during the fourth molting stage and the beginning of the fifth instar, and then its expression decreased gradually until it disappeared at the end of the fifth instar and the wandering stage. (2) We identified a FTZ-F1 response element 390bp upstream of the transcription initiation site of the fibH promoter. (3) BmFTZ-F1 interacted with the basic helix-loop-helix transcription factor Bmdimm. (4) BmFTZ-F1 down-regulated fibH promoter activity and counteracted the effect of Bmdimm on fibH expression.
  
  
  
  Integrating these results, we conclude that BmFTZ-F1 regulates the transcription of fibH by binding to the FTZ-F1 response element in the fibH promoter and counteracts the effect of Bmdimm on fibH expression.
  
  
  
  These findings provide new insights into the mechanism of regulation of the silk protein gene.
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, PR China.
authors.forename: Chunyan
authors.initials: C
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, PR China.
authors.forename: Xingfu
authors.initials: X
authors.lastname: Zha
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, PR China.
authors.forename: Panpan
authors.initials: P
authors.lastname: Shi
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, PR China.
authors.forename: Peng
authors.initials: P
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, PR China.
authors.forename: He
authors.initials: H
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, PR China.
authors.forename: Renwen
authors.initials: R
authors.lastname: Zheng
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, PR China. Electronic address: xiaqy@swu.edu.cn.
authors.forename: Qingyou
authors.initials: Q
authors.lastname: Xia
mesh_terms: D000818:Animals; D012831:Bombyx / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004441:Ecdysterone / Q000494:pharmacology; D005088:Exocrine Glands / Q000187:drug effects / Q000378:metabolism; D005349:Fibroins / Q000235:genetics / Q000378:metabolism*; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D020218:Response Elements; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D019476:Insect Proteins; D014157:Transcription Factors; C482288:fibroin, silkworm; C499713:nuclear hormone receptor FTZ-F1, Bombyx mori; D004441:Ecdysterone; D005349:Fibroins
keywords: 20-Hydroxyecdysone; FTZ-F1; Fibroin heavy chain; Nuclear hormone receptor