Limits...
Tetrahymena metallothioneins fall into two discrete subfamilies.

Díaz S, Amaro F, Rico D, Campos V, Benítez L, Martín-González A, Hamilton EP, Orias E, Gutiérrez JC - PLoS ONE (2007)

Bottom Line: We report the results of phylogenetic and gene expression analyses that include two new Tetrahymena thermophila metallothionein genes (MTT3 and MTT5).Conserved DNA motifs with potential regulatory significance were identified, in an unbiased way, upstream of the start codons of subfamily 7a MTs.EST evidence for alternative splicing in the 3' UTR of the MTT5 mRNA with potential regulatory activity is reported.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Microbiología-III, Facultad de Biología, Universidad Complutense (UCM), Spain.

ABSTRACT

Background: Metallothioneins are ubiquitous small, cysteine-rich, multifunctional proteins which can bind heavy metals.

Methodology/principal findings: We report the results of phylogenetic and gene expression analyses that include two new Tetrahymena thermophila metallothionein genes (MTT3 and MTT5). Sequence alignments of all known Tetrahymena metallothioneins have allowed us to rationalize the structure of these proteins. We now formally subdivide the known metallothioneins from the ciliate genus Tetrahymena into two well defined subfamilies, 7a and 7b, based on phylogenetic analysis, on the pattern of clustering of Cys residues, and on the pattern of inducibility by the heavy metals Cd and Cu. Sequence alignment also reveals a remarkably regular, conserved and hierarchical modular structure of all five subfamily 7a MTs, which include MTT3 and MTT5. The former has three modules, while the latter has only two. Induction levels of the three T. thermophila genes were determined using quantitative real time RT-PCR. Various stressors (including heavy metals) brought about dramatically different fold-inductions for each gene; MTT5 showed the highest fold-induction. Conserved DNA motifs with potential regulatory significance were identified, in an unbiased way, upstream of the start codons of subfamily 7a MTs. EST evidence for alternative splicing in the 3' UTR of the MTT5 mRNA with potential regulatory activity is reported.

Conclusion/significance: The small number and remarkably regular structure of Tetrahymena MTs, coupled with the experimental tractability of this model organism for studies of in vivo function, make it an attractive system for the experimental dissection of the roles, structure/function relationships, regulation of gene expression, and adaptive evolution of these proteins, as well as for the development of biotechnological applications for the environmental monitoring of toxic substances.

Show MeSH

Related in: MedlinePlus

Hierarchical modular structure of the DNA sequence in the MTT5 5′ flanking region.The two major tandem 416-bp repeats are delimited by blank lines; a three-bp gap (dashed) has been introduced in the first repeat in order to facilitate visual detection of the two repeats. Grey highlight: MTCM1 motif; underlined: degraded versions of MTCM1. Aqua (TCA) and yellow (TGA) shading within MTCM1: elements of the AP1 binding site-like heptanucleotide TGA(A/T)TCA, and of a TCATGA palindromic hexanucleotide that overlaps the AP1-like site; this shading is included to facilitate visual identification of the orientation of various MTCM1 copies. Nucleotide substitutions between the two repeats are boxed. Underlined ATG at the end of the sequence: MTT5 start codon.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC1808422&req=5

pone-0000291-g007: Hierarchical modular structure of the DNA sequence in the MTT5 5′ flanking region.The two major tandem 416-bp repeats are delimited by blank lines; a three-bp gap (dashed) has been introduced in the first repeat in order to facilitate visual detection of the two repeats. Grey highlight: MTCM1 motif; underlined: degraded versions of MTCM1. Aqua (TCA) and yellow (TGA) shading within MTCM1: elements of the AP1 binding site-like heptanucleotide TGA(A/T)TCA, and of a TCATGA palindromic hexanucleotide that overlaps the AP1-like site; this shading is included to facilitate visual identification of the orientation of various MTCM1 copies. Nucleotide substitutions between the two repeats are boxed. Underlined ATG at the end of the sequence: MTT5 start codon.

Mentions: The 5′-UTR of MTT5 has an unusual characteristic; a 416 bp tandem duplication in the putative promoter region (Figs. 2 and 7). The first copy is located from −212 to −628; the second copy (from −629 to −1,042) is contiguous with the first, but 3 bp shorter (Fig. 2). The copies are 96% identical to one another. The five copies of MTCM1 motif within each repeat show a striking periodicity of approximately every 54 bp (Fig. 7). The MTCM1 motif is the most conserved segment within the 54-bp repeat units.


Tetrahymena metallothioneins fall into two discrete subfamilies.

Díaz S, Amaro F, Rico D, Campos V, Benítez L, Martín-González A, Hamilton EP, Orias E, Gutiérrez JC - PLoS ONE (2007)

Hierarchical modular structure of the DNA sequence in the MTT5 5′ flanking region.The two major tandem 416-bp repeats are delimited by blank lines; a three-bp gap (dashed) has been introduced in the first repeat in order to facilitate visual detection of the two repeats. Grey highlight: MTCM1 motif; underlined: degraded versions of MTCM1. Aqua (TCA) and yellow (TGA) shading within MTCM1: elements of the AP1 binding site-like heptanucleotide TGA(A/T)TCA, and of a TCATGA palindromic hexanucleotide that overlaps the AP1-like site; this shading is included to facilitate visual identification of the orientation of various MTCM1 copies. Nucleotide substitutions between the two repeats are boxed. Underlined ATG at the end of the sequence: MTT5 start codon.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC1808422&req=5

pone-0000291-g007: Hierarchical modular structure of the DNA sequence in the MTT5 5′ flanking region.The two major tandem 416-bp repeats are delimited by blank lines; a three-bp gap (dashed) has been introduced in the first repeat in order to facilitate visual detection of the two repeats. Grey highlight: MTCM1 motif; underlined: degraded versions of MTCM1. Aqua (TCA) and yellow (TGA) shading within MTCM1: elements of the AP1 binding site-like heptanucleotide TGA(A/T)TCA, and of a TCATGA palindromic hexanucleotide that overlaps the AP1-like site; this shading is included to facilitate visual identification of the orientation of various MTCM1 copies. Nucleotide substitutions between the two repeats are boxed. Underlined ATG at the end of the sequence: MTT5 start codon.
Mentions: The 5′-UTR of MTT5 has an unusual characteristic; a 416 bp tandem duplication in the putative promoter region (Figs. 2 and 7). The first copy is located from −212 to −628; the second copy (from −629 to −1,042) is contiguous with the first, but 3 bp shorter (Fig. 2). The copies are 96% identical to one another. The five copies of MTCM1 motif within each repeat show a striking periodicity of approximately every 54 bp (Fig. 7). The MTCM1 motif is the most conserved segment within the 54-bp repeat units.

Bottom Line: We report the results of phylogenetic and gene expression analyses that include two new Tetrahymena thermophila metallothionein genes (MTT3 and MTT5).Conserved DNA motifs with potential regulatory significance were identified, in an unbiased way, upstream of the start codons of subfamily 7a MTs.EST evidence for alternative splicing in the 3' UTR of the MTT5 mRNA with potential regulatory activity is reported.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Microbiología-III, Facultad de Biología, Universidad Complutense (UCM), Spain.

ABSTRACT

Background: Metallothioneins are ubiquitous small, cysteine-rich, multifunctional proteins which can bind heavy metals.

Methodology/principal findings: We report the results of phylogenetic and gene expression analyses that include two new Tetrahymena thermophila metallothionein genes (MTT3 and MTT5). Sequence alignments of all known Tetrahymena metallothioneins have allowed us to rationalize the structure of these proteins. We now formally subdivide the known metallothioneins from the ciliate genus Tetrahymena into two well defined subfamilies, 7a and 7b, based on phylogenetic analysis, on the pattern of clustering of Cys residues, and on the pattern of inducibility by the heavy metals Cd and Cu. Sequence alignment also reveals a remarkably regular, conserved and hierarchical modular structure of all five subfamily 7a MTs, which include MTT3 and MTT5. The former has three modules, while the latter has only two. Induction levels of the three T. thermophila genes were determined using quantitative real time RT-PCR. Various stressors (including heavy metals) brought about dramatically different fold-inductions for each gene; MTT5 showed the highest fold-induction. Conserved DNA motifs with potential regulatory significance were identified, in an unbiased way, upstream of the start codons of subfamily 7a MTs. EST evidence for alternative splicing in the 3' UTR of the MTT5 mRNA with potential regulatory activity is reported.

Conclusion/significance: The small number and remarkably regular structure of Tetrahymena MTs, coupled with the experimental tractability of this model organism for studies of in vivo function, make it an attractive system for the experimental dissection of the roles, structure/function relationships, regulation of gene expression, and adaptive evolution of these proteins, as well as for the development of biotechnological applications for the environmental monitoring of toxic substances.

Show MeSH
Related in: MedlinePlus