Heat and sodium arsenite act synergistically on the induction of heat shock gene expression in Xenopus laevis A6 cells

Abstract

Heat shock protein (HSP) synthesis was studied in the Xenopus epithelial cell line A6 in response to heat and sodium arsenite, either singly or together. Temperatures of 33–35 °C consistently brought about the synthesis of HSPs at 87,73,70,54,31, and 30 kilodaltons (kDa), whereas sodium arsenite at 25–100 μM induced the synthesis of HSPs at 73 and 70 kDa. In cultures exposed to 10 μM sodium arsenite at 30 °C, HSP synthesis in the 68- to 73-kDa and 29- to 31-kDa regions was much greater than the HSP synthesis in response to each treatment individually. RNA dot blot analysis using homologous genomic subclones revealed that heat shock induced the accumulation of HSP 70 and 30 mRN As. The sizes of the HSP 70 and 30 mRN As determined by Northern hybridization were 2.7 and 1.5 kilobases, respectively. Sodium arsenite (10–100 μM) also induced the accumulation of both HSP 70 and 30 mRNAs. Finally, a mild heat shock (30 °C) plus a low concentration of sodium arsenite (10 μM) acted synergistically on HSP 70 and 30 mRN A accumulation in A6 cells. Thus sodium arsenite and heat act synergistically at the level of both HSP synthesis and HSP mRNA accumulation.