Expression of hsp70 induced in CHO cells by 45.0 degrees C hyperthermia is cell cycle associated and DNA synthesis dependent.

In response to a heat shock, the synthesis of heat shock proteins with a molecular weight of 72 kD (hsp72) is induced. To determine whether hsp72 expression in Chinese hamster ovary (CHO) cells is cell cycle associated, flow cytometry was used to measure DNA content and heat shock protein levels simultaneously. After 10 min at 45.0 degrees C and incubation at 37 degrees C for several hours, hsp72 was induced to a high level in early S phase. Inhibitors of DNA synthesis, aphidicolin, and 1-beta-D-arabinofuranosylcytosine (araC), suppressed the induction of hsp72 but did not inhibit it completely. Hsp73 (constitutive hsp70) was also induced by heat shock, but the induction was uniform through the cell cycle and it was not suppressed by araC.