Phosphorylation of the 90 kDa heat shock protein in heat shocked HeLa cell lysates

The 90 kDa heat shock protein (hsp 90) is a major phosphorylated protein under normal growth conditions. However, it does not incorporate detectable levels of phosphate by incubation of control HeLa cell lysates with [γ- 32P]ATP in vitro. In this paper we show that strong phosphorylation of hsp 90 occurs in lysates prepared from heat shocked HeLa cells. Possible involvement of the eukaryotic initiation factor 2 kinase of the heme-controlled repressor of translation is discussed.