The role of PKN in the regulation of alphaB-crystallin expression via heat shock transcription factor 1.

We previously reported that PKN, a fatty acid-activated serine/threonine protein kinase, translocates from the cytosol to the nucleus by stresses such as heat shock, sodium arsenite, and serum starvation. To clarify the role of PKN under heat stress, we examined whether PKN regulates the expression of heat shock proteins. Co-expression of heat shock transcription factor 1 (HSF1) and the catalytically active fragment of PKN induced the accumulation of alphaB-crystallin but not HSP27 and HSP70 in HeLa S3 cells. The expression of the reporter gene for alphaB-crystallin promoter was activated by co-expression of HSF1 and the catalytically active fragment of PKN, and this activation was dependent on the protein kinase activity of PKN. Deletion analysis of the alphaB-crystallin promoter region revealed that both the proximal and the distal heat shock elements were necessary for the transactivation. These results raise the possibility that there is a signal transduction pathway mediating stress signals for the accumulation of alphaB-crystallin by HSF1 and PKN.