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Scientific article
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Multiple Layers of Regulation of Human Heat Shock Transcription Factor 1

Published inMolecular and cellular biology, vol. 15, no. 8, p. 4319-4330
Publication date2023-03-30
First online date2023-03-30
Abstract

Upon heat stress, monomeric human heat shock transcription factor 1 (hHSF1) is converted to a trimer, acquires DNA-binding ability, is transported to the nucleus, and becomes transcriptionally competent. It was not known previously whether these regulatory changes are caused by a single activation event or whether they occur independently from one another, providing a multilayered control that may prevent inadvertant activation of hHSF1. Comparison of wild-type and mutant hHSF1 expressed in Xenopus oocytes and human HeLa cells suggested that retention of hHSF1 in the monomeric form depends on hydrophobic repeats (LZ1 to LZ3) and a carboxy-terminal sequence element in hHSF1 as well as on the presence of a titratable factor in the cell. Oligomerization of hHSF1 appears to induce DNA-binding activity as well as to uncover an amino-terminally located nuclear localization signal. A mechanism distinct from that controlling oligomerization regulates the transcriptional competence of hHSF1. Components of this mechanism were mapped to a region, including LZ2 and nearby sequences downstream from LZ2, that is clearly separated from the carboxy-terminally located transcription activation domain(s). We propose the existence of a fold-back structure that masks the transcription activation domain in the unstressed cell but is opened up by modification of hHSF1 and/or binding of a factor facilitating hHSF1 unfolding in the stressed cell. Activation of hHSF1 appears to involve at least two independently regulated structural transitions.

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Citation (ISO format)
ZUO, Jianru, RUNGGER, Duri, VOELLMY, Richard. Multiple Layers of Regulation of Human Heat Shock Transcription Factor 1. In: Molecular and cellular biology, 2023, vol. 15, n° 8, p. 4319–4330. doi: 10.1128/MCB.15.8.4319
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ISSN of the journal0270-7306
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