Activation of heat shock transcription factor 1 to a DNA binding form during the G1 phase of the cell cycle

AUTOR(ES)

Bruce, Jacqueline L.

FONTE

Cell Stress Society International

RESUMO

The heat shock transcription factor (HSF) genes encode proteins that bind to the heat shock elements (HSE) of stress-inducible genes. We have observed the induction of HSF1, the ubiquitous member of the HSF family from a latent cytoplasmic state to a form competent to bind HSE during early G1 in HeLa cells in the absence of stress. The induction of DNA-binding HSF1 coincided with a burst in cellular protein synthesis in early G1 and inhibition of this translational peak prevented the formation of DNA binding-activated HSF1. A potential role for HSF1 in cell cycle regulation was suggested by the finding that cell lines stably overexpressing HSF1 showed an increased proportion of G1 cells relative to other cell cycle phases. However, in contrast to the effects of heat shock, entry into G1 did not lead to HSF1 hyperphosphorylation or increased activity of a heat shock promoter-reporter gene and did not cause the induction of heat shock protein 70 expression. Thus HSF1, previously implicated in the heat shock response is activated to a DNA binding from in G1 under non-stress conditions and may play a role in G1 regulation that does not involve the transcription of heat shock genes.

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