Abstract
CONCLUSION Our research has focused on the regulation of the hsp70 and hsc70 genes in 9L RBT cells. Previous studies indicated that both of HSP70 and HSC70 are highly similar in their function, DNA sequence and gene regulation. In our studies, there is differential expression kinetic between HSP70 and HSC70, and the interaction of promoters and transcription factors is distinguishable. Furthermore, only HSC70 is enhanced under geldanamycin treatment, but both of HSP70 and HSC70 are induced under cadmium treatment in 9L RBT cells. For studing the difference, we studied the activation steps of HSF1 including trimerization, phosphorylation, DNA binding ability and protein expression. These results reveal that the phosphorylation is essential for the expression of HSP70, but not for expression of HSC70. On the other hand, we also studied the signal transduction involving in the stress protein induction. These results indicated that the ERK1/2 is activated under low concentration cadmium treatment for activating the HSF1. However, when the cells are stressed under high concentration of cadmium, the p38MAPK, not ERK1/2, is activated to phosphorylate the HSF1.