Medical/biological study (experimental study)

Magnetic field exposure stimulates transposition through the induction of DnaK/J synthesis med./bio.

By: Chow KC, Tung WL

Published in: Biochem Biophys Res Commun 2000; 270 (3): 745-748

Transposable elements are found in all organisms and it is believed that they play an important role in evolution. For some organisms it has been shown that transposition activity can be induced by stressing factors (as heat shock and UV radiation).
Controls were performed with bacterial SURE strains that have been additionally transformed with different plasmids for the inductive over-expression of the heat shock proteins DnaK/DnaJ (HSP70/HSP40) and GroEL/ES. Since DnaK and GroEL are known to be involved in homologous recombination, they are possible participants in mediating the Tn5 transposition stimulation.The controls were incubated for 3 hours in a 37°C water bath.

Exposure	Parameters
Exposure 1: 50 Hz Exposure duration: continuous, 1 h	magnetic flux density: 1.2 mT peak value (unspecified)

Exposure source	Helmholtz coils 15 cm radius
Setup	Culture tubes were fixed in the center of the coil radius
Additional info	another tube, which served as the control, fixed in another Helmholtz coil system with power supply turned off.

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1.2 mT	peak value	measured	unspecified	-

Exposed system:

bacterium
E. coli/SURE (donor strain; carries transposon Tn5; kanamycin/tetracycline resistent; some cultures additionally transformed with plasmids for inductive over-expression of DnaK/J & GroEL/ES); BL21(DE3)pLys (as recipient; chloramphenicol resistent)

genotoxicity/mutation: transposition activity/number of successful conjugations (number of colonies with appropriate antibiotic resistence (kanamycin/tetracycline/chloramphenicol resistent))
molecular biosynthesis: protein content (DnaK/J and GroEL; immunoblotting, SDS-PAGE)

Investigated system:

Time of investigation:

The data showed that under the conditions defined a magnetic field of 50 Hz stimulated the transposition activity of Tn5 and such stimulation was mediated through the induction of the heat shock protein DnaK/J synthesis.

Study character:

Luukkonen J et al. (2011): Pre-Exposure to 50 Hz Magnetic Fields Modifies Menadione-Induced Genotoxic Effects in Human SH-SY5Y Neuroblastoma Cells
Giorgi G et al. (2011): Effect of extremely low frequency magnetic field exposure on DNA transposition in relation to frequency, wave shape and exposure time
Del Re B et al. (2006): Synthesis of DnaK and GroEL in Escherichia coli cells exposed to different magnetic field signals
Del Re B et al. (2004): Various effects on transposition activity and survival of Escherichia coli cells due to different ELF-MF signals
Del Re B et al. (2003): Extremely low frequency magnetic fields affect transposition activity in Escherichia coli
Li SH et al. (2001): Magnetic field exposure induces DNA degradation
Chow KC et al. (2000): Magnetic field exposure enhances DNA repair through the induction of DnaK/J synthesis
Cairo P et al. (1998): Magnetic field exposure enhances mRNA expression of sigma 32 in E. coli