J. Biol. Chem., Vol. 264, Issue 12, 6810-6816, 04, 1989
Transcriptional and translational analysis of the murine 84- and 86-kDa heat shock proteins
SJ Ullrich, SK Moore and E Appella
Laboratory of Cell Biology, National Cancer Institute, Bethesda, Maryland 20892.
The mammalian 85-90-kDa heat shock protein(s) (hsp) have been shown to
exist as two species of 84 and 86 kDa (Ullrich, S. J., Robinson, E. A.,
Law, L. W., Willingham, M., and Appella, E. (1986) Proc. Natl. Acad. Sci.
U. S. A. 83, 3121-3125). Two cDNA clones corresponding to the two forms
have been isolated which specifically hybridize to either a 2.85- or a
3.0-kilobase pair transcript corresponding to hsp 84 and 86, respectively
(Moore, S. K., Kozak, C., Robinson, E. A., Ullrich, S. J., and Appella, E.
(1987) Gene (Amst.) 56, 29-40, and this paper). The regulation of these hsp
were examined in nontransformed NIH-3T3 and chemically transformed Meth A
cells. The basal level of the hsp 84 mRNA transcript was approximately
2.5-fold greater than the hsp 86 transcript, with a corresponding ratio of
hsp 84 to hsp 86 protein synthesis of approximately 2.5:1. After a
transient heat shock (10 min, 44 degrees C), the rate of transcription of
hsp 84 and 86 increased approximately 4.5- and approximately 7-fold,
respectively, within 0.5 h and remained elevated for approximately 2 h.
Northern blot analysis performed on NIH-3T3 and Meth A cells, during
recovery from a transient heat shock, indicated that in both cells mRNA
levels of both hsp increased rapidly, peaking at 5 h post-heat shock; hsp
84 and 86 transcripts were 1.5- and 2-fold higher than in non-heat-shocked
cells, respectively. The increased rate of hsp synthesis after heat shock
correlated with the increased levels of each transcript in both cell lines.
In the transformed Meth A cells the basal mRNA, hsp synthesis, and steady
state levels of each hsp in vitro were 2-3-fold higher than in the
nontransformed NIH-3T3 cells. In Meth A tumors in vivo, the steady state
level of hsp 84 was reduced compared to in vitro levels. Thus, in normal
and in transformed murine cells, both hsp are heat- inducible,
transcriptionally and translationally, with the transformed cells
expressing higher levels of synthesis of both hsp 84 and 86. The data
suggest that hsp 84 and 86 syntheses are primarily transcriptionally
regulated.
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