Expressed sequence tag

EST Expressed sequence tag. An EST is a partial sequence (typically less than 40C bases) selected from cDNA and used to identify genes expressed in a particuh tissue... 

Expressed Sequence Tag. A short DNA sequence usually representing the most terminal regions of a cDNA clone. 

When the Arabidopsis Expressed Sequence Tag (EST) Database was searched with the tomato fmit Psubunit protein sequence two related cDNAs were identified (Figure 11). cDNA 2 is near full length and has been completely sequenced, cDNA 1 has also been sequenced but currently lacks approximately 100 amino acids of coding region. The two Arabidopsis cDNAs are 81% identical at the protein level and have lower identity to the protein encoded by tomato gene 1, 64 and 63% for cDNA 1 and cDNA 2, respectively. However, both cDNAs encode... 

The major advantage of the tandem mass spectrometry approach compared to MALDI peptide fingerprinting, is that the sequence information obtained from the peptides is more specific for the identification of a protein than simply determining the mass of the peptides. This permits a search of expressed sequence tag nucleotide databases to discover new human genes based upon identification of the protein. This is a useful approach because, by definition, the genes identified actually express a protein. 

Mann, M. (1996). A shortcut to interesting human genes peptide sequence tags, expressed-sequence tags and computers. Trends Biochem. Sci. 21, 494-495. 

TES-32 is the most abundant single protein product secreted by the parasite. It is also heavily labelled by surface iodination of live larvae (Maizels et al., 1984, 1987), and is known by monoclonal antibody reactivity to be expressed in the cuticular matrix of the larval parasite (Page et al, 1992a). TES-32 was cloned by matching peptide sequence derived from gel-purified protein to an expressed sequence tag (EST) dataset of randomly selected clones from a larval cDNA library (Loukas et al., 1999). Because of the high level of expression of TES-32 mRNA, clones encoding this protein were repeatedly sequenced and deposited in the dataset (Tetteh et al., 1999). Full sequence determination showed a major domain with similarity to mammalian C-type (calcium-dependent) lectins (C-TLs), together with shorter N-terminal tracts rich in cysteine and threonine residues. Native TES-32 was then shown to bind to immobilized monosaccharides in a calcium-dependent manner (Loukas et al., 1999). 

Tetteh, K.K.A., Loukas, A., Tripp, C. and Maizels, R.M. (1999) Identification of abundantly-expressed novel and conserved genes from infective stage larvae of Toxocara canis by an expressed sequence tag strategy. Infection and Immunity 67, 4771-4779. 

Expressed Sequence Tags (ESTs) and Computational Biology ... 

Xiao H, Merril, CR, Wu A, Olde B, Moreno R, Kerlavage AR, McCombie WR, Venter JC. Complementary DNA sequencing Expressed Sequence Tags and the Human Genome Project. 

Adams MD et al. 3,400 new expressed sequence tags identify diversity of transcripts in human brain. Nature Genet 1993 4 256-267. 

Ewing B et al. Analysis of expressed sequence tags indicates 35,000 human genes. Nature Genet 2000 25 232-234. 

Ulrich CM, Bigler J, Velicer CM et al. Searching expressed sequence tag databases discovery and confirmation of a common polymorphism in the thymidylate synthase gene. Cancer Epidemiol Biomarkers Prev 2000 9 1381-1385. 

EST Expressed sequence tags are STSs derived from cDNAs (see sequence tagged site, STS). 

Sequence tagged site (STS) Short (200-500 base pairs) DNA sequence that has been identified and located as a single occurrence in the human genome. Detectable by polymerase chain reaction, STSs are useful for localizing and mapping of sequence data reported from different laboratories (see also expressed sequence tags). 

Expressed sequence tag (EST) analysis of cDNAs from specific plant tissues has proved to be a valuable tool for the identification of genes for secondary metabolite biosynthesis.36 We have used this approach to identify two distinct sequences predicted to encode OSCs from cDNA libraries from roots of diploid oat (Avena strigosa).35 One of these sequences is highly homologous to cycloartenol... 

LANGE, B.M., WILDUNG, M.R., STAUBER, E.J., SANCHEZ, C., POUCHNIK, D., CROTEAU, R., Probing essential oil biosynthesis by functional evaluation of expressed sequence tags from mint glandular trichomes, Proc. Natl. Acad. Sci. USA, 2000, 97, 2934-2939. 

Figure 11.2 Gene Ontology assignments of the M. truncatula expressed sequence tags.

Holman, M.A. and S. Munzer, "Intellectual Property Rights in Genes and Gene Fragments A Registration Solution for Expressed Sequence Tags," Iowa L. Rev., 85, 735-848 (2000). 

PMF is generally used to identify proteins that have been previously separated by 2-D GE so that additional information including the molecular weights and isoelectric points can be used to supplement PMF identification. PMF is not well suited for searching expressed sequence tag (EST) databases that contain incomplete gene coding information for particular ESTs and it is not adequate for the analysis of complex protein mixtures in solution. 

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