Plant and Cell Physiology, 2004, Vol. 45, No. 5 627-634
© 2004 Oxford University Press
Ca2+ and Calmodulin Modulate DNA-Binding Activity of Maize Heat Shock Transcription Factor in Vitro
1 Institute of Molecular Cell Biology, Hebei Normal University, Shijiazhuang 050016, P.R. China
2 Institute of Genetics and Physiology, Hebei Academy of Agricultural Sciences, Shijiazhuang 050051, P.R. China
DNA-binding activity of a maize heat shock transcription factor (HSF) was induced by heat shock of a whole cell extract at 44°C. Addition of the calcium ion chelator EGTA reduced the binding of the HSF to heat shock element (HSE) in vitro. Re-addition of CaCl2 to the sample pretreated with EGTA restored the ability of the HSF to bind to DNA. DNA-binding activity of the HSF was also induced by directly adding CaCl2 to a whole cell extract at non-heat-shock temperature, but not by MgCl2. During HS at 44°C, calmodulin (CaM) antagonists chlorpromazine (CPZ) and N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W7) inhibited DNA-binding activity of the HSF in a concentration-dependent manner, but N-(6-aminohexyl)-1-naphthalenesulfonamide (W5), an inactive structural analogue of W7, did not. Addition of antiserum specific to CaM reduced the binding of the HSF to HSE. Re-addition of CaM to the sample pretreated with antiserum could restore the binding activity of the HSF. DNA-binding activity of the HSF was promoted by directly adding CaM to a whole cell extract at 44°C, but not by BSA. Moreover, at non-heat-shock temperature, DNA-binding activity of the HSF was also induced by directly adding CaM to a whole cell extract, but not by BSA. Our observations further confirm the role of Ca2+ in activation of the HSF in plant and provide the first example of the role of CaM in regulation of DNA-binding activity of the HSF. These results suggest that Ca2+ and CaM are involved in HSP gene expression likely through regulating the activity of the HSF.
3 Corresponding authors: E-mail, zhourengang{at}163.com; Fax, +86-311-7065840.