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Mol. Cell. Biol., 07 1996, 3799-3806, Vol 16, No. 7
SH Yang, A Nussenzweig, L Li, D Kim, H Ouyang, P Burgman and GC Li
Previously, we proposed a dual control mechanism for the regulation of the
heat shock response in mammalian cells: a positive control mediated by the
heat shock transcription factor HSF1 and a negative control mediated by the
constitutive heat shock element-binding factor (CHBF). To study the
physiological role of CHBF in the regulation of heat shock response, we
purified CHBF to apparent homogeneity and showed it to be identical to the
Ku autoantigen, a heterodimer consisting of 70-kDa (Ku- 70) and 86-kDa
(Ku-80) polypeptides. To study further the functional significance of
Ku/CHBF in the cellular response to heat shock, we established rodent cell
lines that stably and constitutively overexpressed one or both subunits of
the human Ku protein, and examined the thermal induction of hsp70 and other
heat shock proteins in these Ku-overexpressing ing cells. We show that
expression of the human Ku-70 and Ku-80 subunits jointly or of the Ku-70
subunit alone specifically inhibits heat-induced hsp70 expression.
Conversely, expression of human Ku-80 alone does not have this effect.
Thermal induction of other heat shock proteins in all of the
Ku-overexpressing cell lines appears not to be significantly affected, nor
is the state of phosphorylation or the DNA-binding ability of HSF1
affected. These findings support a model in which hsp70 expression is
controlled by a second regulatory factor in addition to the positive
activation of HSF1. The Ku protein, specifically the Ku-70 subunit, is
involved in the regulation of hsp70 gene expression.
Copyright © 1996, American Society for Microbiology
Modulation of thermal induction of hsp70 expression by Ku autoantigen or its individual subunits
Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
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