Heat shock factor binds to heat shock elements upstream of heat shock protein 70a and Samui genes to confer transcriptional activity in Bombyx mori diapause eggs exposed to 5°C

Insect Biochem Mol Biol. 2011 Nov;41(11):843-51. doi: 10.1016/j.ibmb.2011.06.006. Epub 2011 Jul 18.


To understand the molecular mechanisms of how 5°C-incubation activates mRNA expression of Hsp70a and Samui genes in Bombyx mori diapause eggs, we first searched the 5'-upstream regions of the Hsp70a and Samui genes for heat shock elements (HSEs) and found two regions [Hsp70aHSE-1 (-95 to -58) and -2 (-145 to -121), and SamuiHSE-1 (-84 to -55) and -2 (-304 to -290)] corresponding to HSEs (repeats of nGAAn and/or nTTCn). We cloned four cDNAs encoding heat shock factor (HSF)-a2 (627 amino acids), -b (685 aa), -c (682 aa) and -d (705 aa), which were produced by alternative splicing. When we exposed diapause eggs to 5°C beginning at 2 day post-oviposition to break diapause, HSFd mRNA only increased after chilling for 6-8 days, a pattern very similar to those of Hsp70a and Samui mRNAs. To examine further whether HSFd binds to the respective HSEs, we carried out a gel shift assay using HSFd protein expressed in a cell-free system and the isolated HSEs; migration of the respective digoxigenin(DIG)-labeled HSE-1 and -2 of Hsp70a and Samui was retarded by addition of HSFd; the retarded bands disappeared after addition of the corresponding unlabeled HSE-1 and -2 as competitors, but were not affected by addition of the respective mutated unlabeled HSE-1 and -2. These results indicated that HSFd protein binds to the respective HSEs and may activate mRNA expression of Hsp70a and Samui genes upon exposure of diapause eggs to 5°C.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5' Flanking Region
  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Bombyx / embryology
  • Bombyx / genetics
  • Bombyx / metabolism*
  • Cell-Free System
  • Cloning, Molecular
  • Female
  • HSP70 Heat-Shock Proteins / genetics
  • HSP70 Heat-Shock Proteins / metabolism*
  • Heat-Shock Proteins / genetics
  • Heat-Shock Proteins / metabolism*
  • Insect Proteins / genetics
  • Insect Proteins / metabolism*
  • Male
  • Molecular Sequence Data
  • Ovum / metabolism*
  • RNA, Messenger / metabolism


  • HSP70 Heat-Shock Proteins
  • Heat-Shock Proteins
  • Insect Proteins
  • RNA, Messenger
  • samui protein, Bombyx mori