The role of tonicity responsive enhancer sites in the transcriptional regulation of human hsp70-2 in response to hypertonic stress.
The inducible 70 kDa heat shock proteins (Hsp70) in mice are encoded by two almost identical genes, hsp70.1 and hsp70.3. Studies have found that only hsp70.1 is induced by hypertonic stress while both hsp70.1 and hsp70.3 genes are expressed in response to heat shock stress. It is unclear if the human counterparts, hsp70-2 and hsp70-1, are differentially regulated by heat shock and osmotic stress. This study found that only hsp70-2 was induced by hypertonic stress in human embryonic kidney epithelial cells and fibroblasts, while heat shock stress induced both hsp70-1 and hsp70-2. The human hsp70-2 promoter region contains three TonE (tonicity-responsive enhancer) sites, which were reported to play an important role in the response to hypertonicity. When the reporter plasmids containing different parts of the 5' flanking region of hsp70-2 were transfected into human embryonic kidney epithelial cells or fibroblasts, one TonE site at -135 was found to play a key role in the response to hypertonicity. The inactivation of the TonE site using site-directed mutagenesis led to the complete loss of induction by hypertonicity, which demonstrates the essential role of the TonE site. This suggests that the TonE site and the TonEBP (TonE binding protein) are the major regulators for the cellular response against high osmolarity in human kidney tissue.
Heo
Jee In
JI
Department of Biochemistry, Hallym University College of Medicine, Chuncheon 200-702, Korea.
Lee
Mi Suk
MS
Kim
Jeong Hyun
JH
Lee
Jae Seon
JS
Kim
Jaebong
J
Park
Jae Bong
JB
Lee
Jae Yong
JY
Han
Jeong A
JA
Kim
Jong Il
JI
D024506:5' Flanking Region / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012462:Saline Solution, Hypertonic / Q000494:pharmacology*; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics
D004268:DNA-Binding Proteins; D018840:HSP70 Heat-Shock Proteins; C118125:NFAT5 protein, human; D012462:Saline Solution, Hypertonic; D014157:Transcription Factors