Effect of herbimycin A on hsp30 and hsp70 heat shock protein gene expression in Xenopus cultured cells.

We have examined the effect of herbimycin A, a benzoquinoid ansamycin antibiotic, on the pattern of gene expression in amphibians. Exposure of Xenopus laevis A6 kidney epithelial cells to 1 microgram/mL herbimycin A induced the synthesis of the heat shock proteins hsp30 and hsp70 as well as 33- and 45-kDa proteins. Enhanced synthesis of a 34-kDa protein appears to be specific to herbimycin A because its synthesis did not increase after heat shock (35 degrees C). In addition, the synthesis of hsp30 and hsp70 induced by herbimycin A was accompanied by an increase in their mRNAs. Herbimycin A induced a transient accumulation of hsp30 and hsp70 mRNA, which peaked between 4 and 6 h. Finally, concurrent treatment of cells with 0.5 microgram/mL herbimycin A and a mild heat shock of 27 degrees C yielded a synergistic accumulation of hsp30 and hsp70 mRNA. These studies demonstrate that herbimycin A can induce the expression of a set of stress proteins in amphibians and that concurrent treatment with herbimycin A and mild heat shock has a synergistic effect on the accumulation of hsp30 and hsp70 mRNA.