INDUCTION OF HSP72 AND TRANSIENT NUCLEAR-LOCALIZATION OF HSP78 AND HSP72 CORRELATE WITH THE ACQUISITION AND LOSS OF THERMOTOLERANCE IN POSTIMPLANTATION RAT EMBRYOS
Jm. Thayer et Pe. Mirkes, INDUCTION OF HSP72 AND TRANSIENT NUCLEAR-LOCALIZATION OF HSP78 AND HSP72 CORRELATE WITH THE ACQUISITION AND LOSS OF THERMOTOLERANCE IN POSTIMPLANTATION RAT EMBRYOS, Developmental dynamics, 208(2), 1997, pp. 227-243
A number of cell culture studies have indicated that there is a positi
ve correlation between the induction and decay of thermotolerance and
the kinetics of Hsp72 expression, In this study, we have demonstrated
that, in gestational day 10 embryos, induction and decay of thermotole
rance occur over an 8 hr period, To test the hypothesis that there is
a correlation between loss of thermotolerance and the decline of Hsp72
or Hsp73 gene products over time, expression levels of both Hsp72 and
constitutively expressed Hsp73 mRNAs and proteins were examined at se
veral time points following exposure to a thermotolerance-inducing exp
osure of 42 degrees C, Our results indicated that Hsp72 mRNA was stron
gly induced 1 hr after exposure but no longer detectable by 8 hr, Alth
ough our Western blot results indicated that Hsp72 protein was present
beyond 8 hr after exposure, Northern blot analysis showed that Hsp72
mRNA was no longer present 5 hr after exposure to 42 degrees C, The la
tter finding indicates that no new Hsp72 can be synthesized at this ti
me point and beyond, Although there was very little or no induction of
Hsp73, immunohistochemical analysis revealed a dramatic, transient sh
ift in intracellular localization of Hsp73 protein, as well as Hsp72,
Under non-stress conditions, Hsp73 was cytoplasmically localized but l
ocalization was largely nuclear 1 hr after exposure, when thermotolera
nce was demonstrable, Hsp73 and Hsp72 proteins were no longer localize
d in the nucleus by 8 hr, when thermotolerance was no longer detectabl
e, Thus, the induction of Hsp72 and the transient nuclear localization
of both Hsp72 and Hsp73 correlate with the kinetics of thermotoleranc
e in the postimplantation rat embryo. (C) 1997 Wiley-Liss, Inc.