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Steroid hormone regulation of the gene encoding the chicken heat shock protein hsp 108
Abstract:
We have previously isolated a partial cDNA clone encoding a heat shock protein which has been termed hsp 108 (Zarucki-Schulz, T., Kulomaa, M. S., Headon, D. R., Weigel, N. L., Baez, M., Edwards, D. O., McGuire, W. L., Schrader, W. T., and O'Malley, B. W. (1984) Proc. Natl. Acad. Sci. U.S.A. 81, 6358-6362; Sargan, D. R., Tsai, M.-J., and O'Malley, B. W. (1985) Biochemistry 25, 6252-6258). Here we examine the expression of the hsp 108 gene in steroid-stimulated chick oviducts. After 16 h of secondary stimulation with estrogen or progesterone, a 20-50-fold increase in hsp 108 mRNA is detected above unstimulated levels. RNA quantitation by Rot analysis shows that in these oviducts there are 75 molecules of hsp 108 mRNA/oviduct cell. Nuclear "run-off" assays indicate only a 2-4-fold increase in the rate of transcription of the gene in response to either sex steroid, suggesting that the gene is regulated both at the transcriptional level and by mRNA stabilization. On hormone withdrawal, the concentration of hsp 108 mRNA in the oviduct falls to unstimulated control levels within 4 days. Chronic stimulation of the chicks with estrogen (or high acute doses of estrogen) attenuates specifically the inductive response of the hsp 108 gene, but not of ovalbumin, under these conditions. This is not due to a significant reduction of the transcription rate of the gene. We have previously shown that hsp 108 is expressed constitutively in many tissues of the chick (Sargan, D. R., Tsai, M.-J., and O'Malley, B. W. (1985) Biochemistry 25, 6252-6258). In tissues which are not responsive to hormones, no short-term effects of hormone administration on the gene were observed. In the spleen there is a reproducible slow activation of the gene, but the kinetics of this response suggest that it is not a primary response to the hormone. Thus, this hsp 108 gene codes for an interesting new eucaryotic heat shock protein which is regulated also by steroid hormones in a tissue-specific manner.