Heat shock factor 1 mediates hemin-induced hsp70 gene transcription in K562 erythroleukemia cells.
Transcriptional induction of the hsp70 gene is mediated by heat shock factor 1 (HSF1) rapidly activated upon heat and other stresses. HSF2 has been thought to be responsible for accumulation of HSP70 during hemin-induced differentiation of human K562 erythroleukemia cells because of accompanying acquisition of HSF2 DNA binding activity. However, there has not been any direct evidence for such a functional role of HSF2. The purpose of this study is to clarify the roles of HSF1 and HSF2 in HSP70 induction in hemin-treated K562 cells. We show here that a chimeric polypeptide of HSF2 and GAL4 DNA binding domain (GAL4-BD-HSF2) was unable to induce a GAL4 binding site-containing luciferase reporter gene in response to hemin and that exogenously overproduced HSF2 also failed to increase expression of a heat shock element-containing reporter. On the contrary, expression of a GAL4-BD-HSF1 chimeric protein responded to hemin treatment as well as to heat shock, and transiently overexpressed HSF1 caused hemin-responsive induction of the reporter gene in a dose-dependent manner. These results indicate that HSF1, rather than HSF2, primarily mediates the hemin-induced transcription of the hsp70 gene.
Yoshima
T
T
HSP Research Institute, Kyoto Research Park, Shimogyo-ku, Kyoto 600-8813, Japan.
Yura
T
T
Yanagi
H
H
D001483:Base Sequence; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics*; D000076249:Heat Shock Transcription Factors; D006427:Hemin / Q000502:physiology*; D006801:Humans; D004915:Leukemia, Erythroblastic, Acute / Q000235:genetics / Q000473:pathology; D011993:Recombinant Fusion Proteins / Q000235:genetics; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000502:physiology*; D014407:Tumor Cells, Cultured
D017931:DNA Primers; D004268:DNA-Binding Proteins; C000619706:HSF1 protein, human; D018840:HSP70 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D006427:Hemin