While incubation of HeLa cells for 5–10 min at 45°C does not affect subsequent cellular growth and DNA synthesis at 37°C, there is an increased synthesis of specific proteins in the molecular weight region of 100000, 72000–74000 and 37000. The synthesis of these proteins reaches a maximum 2 h after the heat shock and while the proteins themselves are stable, their synthesis declines to normal levels 4 h afterwards. The increased synthesis is blocked by actinomycin D but the addition of cycloheximide or NaF during the ‘induction’ period is without effect.
Cloned cDNA sequences coding for specific 72 000-74 000 M, HeLa cell heat shock proteins (HSPs) have been used as probes to examine cytoplasmic and nuclear RNA of heat shocked HeLa cells. The mRNAs for these HSPs vary widely in size. Whilst the p-, S-and c-HSPs are encoded in mRNAs of 1.9 kb, the y-HSP arises from an mRNA three times that size. A search for putative nuclear precursors to these mRNAs revealed high M, candidates at 15.8 kb which accumulate 1-2 h after the initial heat shock, thus supporting the notion that transcriptional control is important in the initial heat shock response.
HeLa cellHeat shock response Heat shock protein Messenger RNA Pre-messenger RNA
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