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Category: Microbial Genetics and Molecular Biology; Fungi and Fungal Pathogenesis
Heat Shock Response, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555816636/9781555814731_Chap32-1.gif /docserver/preview/fulltext/10.1128/9781555816636/9781555814731_Chap32-2.gifAbstract:
Increased synthesis of heat shock proteins (hsps) was seen in response to physical and chemical stresses and during developmental transitions. Other stresses, particularly oxidative stress and osmotic stress, elicit characteristic changes in gene expression that overlap with one another and with heat stress. The same regulatory factors may be involved in multiple stress responses. These include the heat shock transcription factor and the stress mitogen-activated protein kinases (MAPKs) Hog1 and Slt2 of Saccharomyces cerevisiae and their orthologs in other organisms. The importance of ubiquitin-dependent proteolysis to the heat shock response is shown by the restorative effect of over-expressing UBI4 on survival of cells that are deficient in hsp synthesis. Heat shock transcription factor (HSF) binds as a trimer to heat shock elements (HSEs) within target gene promoters. The fundamental unit of the HSE is nGAAn repeated in tandem on alternating DNA strands (perfect HSE), with a minimum of three pentanucleotides being required in S. cerevisiae for activity and a five-nucleotide gap between two of the pentanucleotides still supporting induction (gapped HSE). If stress responses were unregulated, they would be detrimental, rather than helpful, as seen when there is a buildup of trehalose, particular sphingolipids, Hsp90, or a hyperactivated Hog1 MAPK.
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A phylogenetic tree generated by ClustalW2 ( Larkin et al., 2007 ) based on multiple sequence alignment of the sHsps of N. crassa, A. nidulans, and S. cerevisiae.
The major stress MAPK pathways of S. cerevisiae and N. crassa. HK, histidine kinase.
Major Hsps of S. cerevisiae and homologs in N. crassa