Eukaryotic Cell doi:10.1128/EC.00221-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.
A combination of two regulatory elements in the Tetrahymena thermophila HSP70-1 gene controls heat shock activation
Sabrina Barchetta*,
Antonietta La Terza,
Patrizia Ballarini,
Sandra Pucciarelli,
and
Cristina Miceli
Department of Molecular, Cellular and Animal Biology, University of Camerino, Via Gentile III da Varano, 62032 Camerino (MC), Italy
* To whom correspondence should be addressed. Email:
sabrina.barchetta{at}unicam.it.
 |
Abstract |
|---|
The induction of heat shock genes (HSPs) is thought to be primarily regulated by heat shock transcription factors (HSFs), which bind target sequences on HSP promoters, called heat shock elements (HSEs). In this work, we investigated the 5' untranslated regions (UTRs) of the Tetrahymena thermophila HSP 70-1 gene (T.t. HSP 70-1), and we found, in addition to the canonical and divergent HSEs, multiple sets of GATA elements (GATA) that have not been reported previously in protozoa. By means of in vivo analysis of a green fluorescent protein reporter trans-gene driven by the T.t. HSP 70-1 promoter, we demonstrate that HSEs do not represent the minimal regulatory elements for heat shock induction, as the T.t. HSP 70-1 is tightly regulated by both HSE and GATA elements. EMSA analysis also showed that HSFs are constitutively bound to the HSEs, whereas GATA elements are engaged only after heat shock. This is the first demonstration by in vivo analysis of functional HSE and GATA elements in protozoa. Furthermore, we provide evidence of a functional link between HSE and GATA elements in the activation of the heat shock response.
