Confluent cultures of the mouse cell line clone 1D were subjected to 1-hr hyperthermic treatments. Temperatures were increased from the control level of 37° to values ranging from 38 to 45°. Protein synthesis patterns were determined in fluorograms of sodium dodecyl sulfate-polyacrylamide gels labeled with [3H]leucine. Although incorporation into most proteins was either repressed or decreased by heat treatment, several proteins showed an increased label or were apparently induced de novo. Among the induced proteins was a prominent band, probably a doublet, with an estimated molecular weight of 70,000 to 69,000.

Crude cell lysates made from 37°, 41°, and 45°-treated cells were tested for kinase activity at 30° by a 10-min incubation with adenosine [γ-32P]triphosphate. Several specific proteins exhibited increased phosphorylation, while phosphorylation of other proteins decreased. The most significant increase in phosphorylation was shown by a protein with molecular weight of about 37,000. We suggest that heat treatment induces or activates one or more specific phosphokinase(s) with the ability to phosphorylate proteins with approximate molecular weights of 37,000, 36,000, 23,000, and 16,000.

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Supported by NIH Training Grant 2T32 HD-07009-06 from the National Institute of Child Health and Human Development and by NIH Grant CA 14599.

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