Myc-mediated transactivation of HSP70 expression following exposure to magnetic fields.
We investigated c-myc protein-binding sites on the HSP70 promoter as modulators of the induction of HSP70 gene expression in response to magnetic field stimulation (8microT at 60Hz) and whether the presence of c-myc protein potentiates transactivation of HSP70 expression. A 320 base pair region in the HSP70 promoter (+1 to -320) was analyzed. This region contains two c-myc-protein binding sites with consensus sequences located at -230 and -160 nucleotide positions (relative to the transcription initiation site) and overlapping with the region reported for the regulation of HSP70 gene expression by c-myc protein. This promoter region is upstream of other regulatory sequences, including the heat shock element (HSE), AP-2, and serum response element (SRE). Transfectants containing both c-myc protein-binding sites, HSP-MYC A and HSP-MYC B, and exposed to magnetic fields showed a 3.0-fold increase in expression of CAT activity as compared with sham-exposed control transfectants. Transfectants containing one c-myc binding site, HSP-MYC A, and exposed to magnetic fields showed a 2.3-fold increase in CAT expression. Transfectants in which both HSP-MYC A and HSP-MYC B binding sites were deleted showed no magnetic field sensitivity; values were virtually identical with sham-exposed controls. If the c-myc expression vector was not co-transfected with the constructs containing myc-binding sites, there was no difference in the expression of CAT activity between magnetically stimulated and sham-exposed controls, although both responded to heat shock. These data suggest that endogenous elevated levels of myc protein contribute to the induction of HSP70 in response to magnetic field stimulation.
Lin
H
H
Department of Pathology, Columbia University Health Sciences, New York, New York 10032, USA.
Head
M
M
Blank
M
M
Han
L
L
Jin
M
M
Goodman
R
R
D004574:Electromagnetic Fields; D005786:Gene Expression Regulation / Q000528:radiation effects*; D016259:Genes, myc / Q000528:radiation effects*; D018922:HL-60 Cells; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000528:radiation effects*; D006801:Humans; D011401:Promoter Regions, Genetic / Q000528:radiation effects; D011485:Protein Binding / Q000235:genetics / Q000528:radiation effects; D012313:RNA / Q000378:metabolism / Q000528:radiation effects; D017384:Sequence Deletion; D015533:Transcriptional Activation / Q000528:radiation effects*
D018840:HSP70 Heat-Shock Proteins; D012313:RNA