Abstract
Metallothioneins (MT) are multi-stress proteins mainly involved in metal detoxification. MT gene expression is normally induced by a broad variety of stimulus and its gene expression regulation mainly occurs at a transcriptional level. Conserved motifs in the Tetrahymena thermophila MT promoters have been described. These motifs show a consensus sequence very similar to AP-1 sites, and bZIP type transcription factors might participate in the MT gene expression regulation. In this research work, we characterize four AP-1 transcription factors in each of four different analyzed Tetrahymena species, detecting a high conservation among them. Each AP-1 molecule has its counterpart in the other three Tetrahymena species. A comparative qRT-PCR analysis of these AP-1 genes have been carried out in different T. thermophila strains (including metal-adapted, knockout and/or knockdown strains among others), and under different metal-stress conditions (1 or 24 h Cd2+, Cu2+, or Pb2+ treatments). The possible interaction of these transcription factors with the conserved AP-1 motifs present in MT promoters has been corroborated by protein-DNA interaction experiments. Certain connection between the expression patterns of the bZIP and MT genes seems to exist. For the first time, and based on our findings, a possible gene expression regulation model including both AP-1 transcription factors and MT genes from the ciliate T. thermophila has been elaborated.
Highlights
IntroductionMetallothioneins (MTs) are multi-stress proteins able to chelate metallic cations through their numerous cysteine residues (Gutierrez et al, 2011; de Francisco et al, 2016)
Metallothioneins (MTs) are multi-stress proteins able to chelate metallic cations through their numerous cysteine residues (Gutierrez et al, 2011; de Francisco et al, 2016). They are considered as multifunctional proteins that participate in different biological processes, such as: maintaining of cellular metal homeostasis, protection against toxic metals or indirect protection against reactive oxygen species (ROS) (Vasak, 2005; Diaz et al, 2007)
Four putative AP-1 genes are detected in the T. thermophila macronuclear genome and they have been named; ThebZIP1, TthebZIP2, TthebZIP3, and TthebZIP4
Summary
Metallothioneins (MTs) are multi-stress proteins able to chelate metallic cations through their numerous cysteine residues (Gutierrez et al, 2011; de Francisco et al, 2016). They are considered as multifunctional proteins that participate in different biological processes, such as: maintaining of cellular metal homeostasis, protection against toxic metals (detoxification) or indirect protection against reactive oxygen species (ROS) (Vasak, 2005; Diaz et al, 2007). These motifs show a consensus sequence (GTGTGAATCATGAGT) very similar to the previously reported for AP-1 sites and, it is believed that putative bZIP factors could participate in their gene expression regulation (Diaz et al, 2007; Gutierrez et al, 2011; de Francisco et al, 2016)
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