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Mol. Cell. Biol., Oct 1995, 5268-5278, Vol 15, No. 10
A Nakai, Y Kawazoe, M Tanabe, K Nagata and RI Morimoto
Avian cells express three heat shock transcription factor (HSF) genes
corresponding to a novel factor, HSF3, and homologs of mouse and human HSF1
and HSF2. Analysis of the biochemical and cell biological properties of
these HSFs reveals that HSF3 has properties in common with both HSF1 and
HSF2 and yet has features which are distinct from both. HSF3 is
constitutively expressed in the erythroblast cell line HD6, the lymphoblast
cell line MSB, and embryo fibroblasts, and yet its DNA-binding activity is
induced only upon exposure of HD6 cells to heat shock. Acquisition of HSF3
DNA-binding activity in HD6 cells is accompanied by oligomerization from a
non-DNA-binding dimer to a DNA- binding trimer, whereas the effect of heat
shock on HSF1 is oligomerization of an inert monomer to a DNA-binding
trimer. Induction of HSF3 DNA-binding activity is delayed compared with
that of HSF1. As occurs for HSF1, heat shock leads to the translocation of
HSF3 to the nucleus. HSF exhibits the properties of a transcriptional
activator, as judged from the stimulatory activity of transiently
overexpressed HSF3 measured by using a heat shock element-containing
reporter construct and as independently assayed by the activity of a
chimeric GAL4-HSF3 protein on a GAL4 reporter construct. These results
reveal that HSF3 is negatively regulated in avian cells and acquires
DNA-binding activity in certain cells upon heat shock.
Copyright © 1995, American Society for Microbiology
The DNA-binding properties of two heat shock factors, HSF1 and HSF3, are induced in the avian erythroblast cell line HD6
Department of Cell Biology, Kyoto University, Japan.
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