Testin also known as TESS is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

that in humans is encoded by the ''TES''

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

located on

chromosome 7 Chromosome 7 is one of the 23 pairs of chromosomes in humans, who normally have two copies of this chromosome. Chromosome 7 spans about 159 million base pairs (the building material of DNA) and represents between 5 and 5.5 percent of the total DN ...

. TES is a 47

kDa The dalton or unified atomic mass unit (symbols: Da or u) is a non-SI unit of mass widely used in physics and chemistry. It is defined as of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at re ...

protein composed of 421

amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

found at

focal adhesions In cell biology, focal adhesions (also cell–matrix adhesions or FAs) are large macromolecular assemblies through which mechanical force and regulatory signals are transmitted between the extracellular matrix (ECM) and an interacting cell. More ...

and is thought to have a role in regulation of

cell motility Motility is the ability of an organism to move independently, using metabolic energy. Definitions Motility, the ability of an organism to move independently, using metabolic energy, can be contrasted with sessility, the state of organisms th ...

. In addition to this, TES functions as a

tumour A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

suppressor. The ''TES'' gene is located within a fragile region of

, and the promoter elements of the ''TES'' gene have been shown to be susceptible to

methylation In the chemical sciences, methylation denotes the addition of a methyl group on a substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replacing a hydrogen atom. These t ...

– this prevents the

expression Expression may refer to: Linguistics * Expression (linguistics), a word, phrase, or sentence * Fixed expression, a form of words with a specific meaning * Idiom, a type of fixed expression * Metaphorical expression, a particular word, phrase, o ...

of the TES protein. TES came to greater prominence towards the end of 2007 as a potential mechanism for its tumour suppressor function was published.

Domain organisation

Tes is composed of the following domains: The structures of the Cysteine rich domain and the PET domain are not known. LIM domains, however, are known as modulators of protein interactions. LIM domain consist of 2

zinc fingers A zinc finger is a small protein structural motif that is characterized by the coordination of one or more zinc ions (Zn2+) in order to stabilize the fold. It was originally coined to describe the finger-like appearance of a hypothesized struct ...

separated by 2 hydrophobic amino acids (generally a

phenylalanine Phenylalanine (symbol Phe or F) is an essential α-amino acid with the formula . It can be viewed as a benzyl group substituted for the methyl group of alanine, or a phenyl group in place of a terminal hydrogen of alanine. This essential amino a ...

and then a

leucine Leucine (symbol Leu or L) is an essential amino acid that is used in the biosynthesis of proteins. Leucine is an α-amino acid, meaning it contains an α-amino group (which is in the protonated −NH3+ form under biological conditions), an α- ca ...

Binding partners

TES does not appear to be an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

; rather it is a protein that mediates/regulates cellular functions via protein–protein interactions. Pull down experiments reveal that TES has putative interactions mediated by the indicated domain: Garvalov ''et al.'' showed that the interaction between TES & zyxin were direct, using recombinant proteins expressed in ''

E. coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Escher ...

''. Some of the potential binding partners (Zyxin, mENA) can be found in

focal adhesion In cell biology, focal adhesions (also cell–matrix adhesions or FAs) are large macromolecular assemblies through which mechanical force and regulatory signals are transmitted between the extracellular matrix (ECM) and an interacting cell. More ...

complexes; the range of binding partners indicates a potential role for TES in-between 'privileged'

Actin Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. It is found in essentially all eukaryotic cells, where it may be present at a concentration of over ...

polymerisation and focal adhesion contacts to the

extracellular matrix In biology, the extracellular matrix (ECM), also called intercellular matrix, is a three-dimensional network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide stru ...

. This tallies with the observation that

GFP GFP may refer to: Organisations * Gaelic Football Provence, a French Gaelic Athletic Association club * Geheime Feldpolizei, the German secret military police during the Second World War * French Group for the Study of Polymers and their Applicat ...

-tagged TES can be seen at focal adhesions.

TES as a tumour suppressor

In December 2007, Boeda, Briggs et al. showed that the third LIM domain of TES displaces Mena from its usual subcellular positions (

or the cell leading edge). The ENA/VASP protein family (of which Mena is a member) are anchored to specific proteins within the cell by a

peptide Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. A ...

motif consisting of a

residue, followed by four

proline Proline (symbol Pro or P) is an organic acid classed as a proteinogenic amino acid (used in the biosynthesis of proteins), although it does not contain the amino group but is rather a secondary amine. The secondary amine nitrogen is in the prot ...

residues – known as a FPPPP motif. It is the

EVH1 domain WH1 domain is an evolutionary conserved protein domain. Therefore, it has an important function. Function WH1 domains are found on WASP proteins, which are often involved in actin polymerization. Hence, WH1 is important for all cellular process ...

s of VASP/EVL proteins that directly contact the FPPPP motif. The precise architecture of TES:MENA binding was revealed by

X-ray crystallography X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

, and showed that the 3rd LIM domain of TES covered up the FPPPP binding site within Menas EVH1 domain.

Isothermal titration calorimetry Isothermal titration calorimetry (ITC) is a physical technique used to determine the thermodynamic parameters of interactions in solution. It is most often used to study the binding of small molecules (such as medicinal compounds) to larger macrom ...

showed that TES has a greater affinity for Mena than its canonical FPPPP ligand, as presented in the focal adhesion protein zyxin. Using microscopy it was shown that either over-expression of

-tagged TES, or just the tagged third LIM domain displaced Mena from focal adhesions and reduced mean cell velocity. These finding were significant given that Mena is often over-expressed in cancer cells, and is thought to be partly responsible for cancer cell motility, and therefore a factor in cancer

metastasis Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, then, ...

. TES is conversely often not produced in cancer cells. It is possible that a drug designed to mimic TES's interaction with Mena could be used to prevent metastasis and thus development of secondary tumours in cancer patients. The work was widely reported in the British press (the work was carried out by

Cancer Research UK Cancer Research UK (CRUK) is the world's largest independent cancer research organization. It is registered as a charity in the United Kingdom and Isle of Man, and was formed on 4 February 2002 by the merger of The Cancer Research Campaign and t ...

), and also in the international press.

Conformational change

Based on the observations that: *Mammalian cell derived TES binding Zyxin *

-produced recombinant TES (rTES) does not bind Zyxin *An rTES construct composed of residues 201–421 (i.e., the linker and all 3 LIM domains) does bind Zyxin *The above rTES construct binds an N-terminal rTES construct, consisting of the cysteine rich and PET domains – ''IE, the two-halves of TES interact with each other''. Garvalov ''et al.'' propose that TES exists in two conformational states: A 'closed' state where the N & C halves of TES interact, obscuring the Zyxin binding site in LIM1, and an 'open' state where the Zyxin binding site is accessible and the two halves no-longer interact in the same fashion, if at all. The regulatory mechanism switching between the two states is not presently fully understood.

Phenotype

RNAi RNA interference (RNAi) is a biological process in which RNA molecules are involved in sequence-specific suppression of gene expression by double-stranded RNA, through translational or transcriptional repression. Historically, RNAi was known by o ...

experiments, cells that had impaired TES expression showed an inability to correctly organise their

and

actin Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. It is found in essentially all eukaryotic cells, where it may be present at a concentration of over ...

stress fibres. In gene knockout experiments,

transgenic A transgene is a gene that has been transferred naturally, or by any of a number of genetic engineering techniques, from one organism to another. The introduction of a transgene, in a process known as transgenesis, has the potential to change the ...

mice lacking both copies of the TES gene displayed an increased susceptibility to

formation when challenged with a carcinogen. Mice retaining the TES gene were less susceptible: thus, TES is a tumour suppressor gene.

References

{{Reflist, 30em EVH1 domain