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 mu g/mL herbimycin A induced the synthesis of the heat shock proteins hsp30 and hsp70 as w ell 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 o f hsp30 and hsp70 induced by herbimycin A was accompanied by an increa se in their mRNAs. Herbimycin A induced a transient accumulation of hs p30 and hsp70 mRNA, which peaked between 4 and 6 h. Finally, concurren t treatment of cells with 0.5 mu g/mL herbimycin A anti a mild heat sh ock of 27 degrees C yielded a synergistic accumulation of hsp30 and hs p70 mRNA. These studies demonstrate that herbimycin A can induce the e xpression of a set of stress proteins in amphibians and that concurren t treatment with herbimycin A and mild heat shock has a synergistic ef fect on the accumulation of hsp30 and hsp70 mRNA.