Thyroid hormone receptor modulates the expression of the rabbit cardiac sarco (endo) plasmic reticulum Ca(2+)-ATPase gene.

We have analyzed the effect of thyroid hormone (T3) on SERCA2 gene expression using fetal chicken primary cardiac myocytes and C2C12 skeletal muscle cells in culture. Northern blot analysis of both cell types demonstrated that T3 induced a 3-fold accumulation of SERCA2 mRNA compared with cells grown in medium lacking T3. We have engineered deletion constructs containing various lengths of the 5'-flanking region from the rabbit SERCA2 gene which we have cloned previously (Zarain-Herzberg, A., MacLennan, D. H., and Periasamy, M. (1990) J. Biol. Chem. 265, 4670-4677). A stable transfectant in C2C12 containing a chimeric SERCA2/CAT gene construct including -254 base pairs (bp) of SERCA2 5'-flanking region showed increased transcription activity upon the addition of 50 nM T3. We have analyzed the expression of several deletion constructs spanning 1,102 bp of the 5'-up-stream sequence of the SERCA2 gene by functional expression assays. Transient coexpression of the T3 receptor alpha 1 with various SERCA2/CAT deletion constructs showed trans-activation of chimeric constructs containing more than -267 bp, indicating that a thyroid hormone-responsive element was localized, at least in part, to the region -267 to -72 bp. T3 receptor-DNA binding assays demonstrated binding of the rat T3 receptor alpha 1 to a fragment containing a proposed T3 response element located between position -254 and -72 in the 5'-flanking region of the SERCA2 gene.