REGULATION OF HSP70 AND HSP28 GENE-EXPRESSION - ABSENCE OF COMPENSATORY INTERACTIONS

We have previously reported the lack of HSP28 gene expression during a cute and chronic thermotolerance development in L929 cells (J Cell Phy siol 152: 118-125, 1992; Cancer Res 52: 5787, 1992). In contrast to HS P28, an extremely high level of inducible HSP70 synthesis was observed . These results led us to investigate the possibility of compensatory interactions between HSP70 and HSP28. To test the hypothesis, L929 cel ls were transfected with the human HSP28 gene contained in plasmid pCM V27. Data from Western blot and two-dimensional gel electrophoresis of [H-3] leucine and [P-32] orthophosphate-labeled proteins showed the s ynthesis and phosphorylation of HSP28 in transfected cells after heati ng at 45 degrees C for 10 min. However, the expression of constitutive and inducible HSP70 genes, along with the synthesis of their proteins , was not decreased after heat shock. These results suggest an indepen dent regulation of HSP28 and HSP70 gene expression.