Functional characterization of the 5'-upstream region of MTT5 metallothionein gene from Tetrahymena thermophila.
Metallothioneins are ubiquitous small, cysteine-rich, metal-binding proteins that play important roles in intracellular metal homeostasis and detoxification. Very few data are available on the promoter region and the mechanism of metallothionein transcription in Protozoa. In this study, we focused on Tetrahymena thermophila MTT5 5'-flanking region. To define the sequence elements underlying the metal-responsiveness of this promoter, we constructed a series of deletions and mutations starting with a 1777 bp fragment immediately upstream of the start codon of MTT5. As a reporter gene we used the previously tested IAG52B surface antigen from the protozoan fish parasite Ichthyophthirius multifiliis. The results suggest that a region spanning between -300 bp and -274 bp, dubbed Tetrahymena thermophila Cadmium-Response-Element (TtCdRE), is necessary to elicit high-level expression of the transgene following induction with cadmium. This is the first demonstration by in vivo analyses of a regulatory element essential for Cd-mediated control of protozoan metallothionein gene expression, where the sequence GATA appears to be involved.
Formigari
Alessia
A
Department of Biology, University of Padova, Via Ugo Bassi 58/B, 35100 Padova, Italy.
Boldrin
Francesco
F
Santovito
Gianfranco
G
Cassidy-Hanley
Donna
D
Clark
Theodore G
TG
Piccinni
Ester
E
D000818:Animals; D000953:Antigens, Protozoan / Q000096:biosynthesis / Q000235:genetics; D001665:Binding Sites; D002104:Cadmium / Q000378:metabolism; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D008668:Metallothionein / Q000096:biosynthesis* / Q000235:genetics*; D015800:Protozoan Proteins / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid; D017384:Sequence Deletion; D016808:Tetrahymena thermophila / Q000235:genetics* / Q000502:physiology
D000953:Antigens, Protozoan; D015800:Protozoan Proteins; D002104:Cadmium; D008668:Metallothionein