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The human L-threonine 3-dehydrogenase gene is an expressed pseudogene.

Edgar AJ - BMC Genet. (2002)

Bottom Line: These truncated proteins are the result of 3 mutations within the gene.There is a SNP, A to G, present in the genomic DNA sequence of some individuals which results in the loss of the acceptor splice site preceding exon 4.The acceptor splice site preceding exon 6 was lost in all 23 individuals genotyped and there is an in-frame stop codon in exon 6 (CGA to TGA) resulting in arginine-214 being replaced by a stop codon.

View Article: PubMed Central - HTML - PubMed

Affiliation: Tissue Engineering & Regenerative Medicine Centre, Division of Investigative Science, Faculty of Medicine, Imperial College of Science, Technology and Medicine, Chelsea & Westminster Hospital, London, United Kingdom. alasdair.edgar@ic.ac.uk

ABSTRACT

Background: L-threonine is an indispensable amino acid. One of the major L-threonine degradation pathways is the conversion of L-threonine via 2-amino-3-ketobutyrate to glycine. L-threonine dehydrogenase (EC 1.1.1.103) is the first enzyme in the pathway and catalyses the reaction: L-threonine + NAD+ = 2-amino-3-ketobutyrate + NADH. The murine and porcine L-threonine dehydrogenase genes (TDH) have been identified previously, but the human gene has not been identified.

Results: The human TDH gene is located at 8p23-22 and has 8 exons spanning 10 kb that would have been expected to encode a 369 residue ORF. However, 2 cDNA TDH transcripts encode truncated proteins of 157 and 230 residues. These truncated proteins are the result of 3 mutations within the gene. There is a SNP, A to G, present in the genomic DNA sequence of some individuals which results in the loss of the acceptor splice site preceding exon 4. The acceptor splice site preceding exon 6 was lost in all 23 individuals genotyped and there is an in-frame stop codon in exon 6 (CGA to TGA) resulting in arginine-214 being replaced by a stop codon. These truncated proteins would be non-functional since they have lost part of the NAD+ binding motif and the COOH terminal domain that is thought to be involved in binding L-threonine. TDH mRNA was present in all tissues examined.

Conclusions: The human L-threonine 3-dehydrogenase gene is an expressed pseudogene having lost the splice acceptor site preceding exon 6 and codon arginine-214 (CGA) is mutated to a stop codon (TGA).

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Amplicons from 3 individuals for the exon 6 splice acceptor site were digested with the restriction enzyme Hsp92II. All amplicons were digested showing loss of the splice site. Undigested samples, UD and digested samples, D.
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Figure 7: Amplicons from 3 individuals for the exon 6 splice acceptor site were digested with the restriction enzyme Hsp92II. All amplicons were digested showing loss of the splice site. Undigested samples, UD and digested samples, D.

Mentions: Amplicons from the exon 6 splice acceptor site from 3 individuals were digested with the restriction enzyme Hsp92II. If the acceptor splice site was not present (CATG^g rather than CATAg) the 207 bp amplicon was digested to produce restriction fragments of 112 and 95 bp. Three individuals examined had lost the splice site (Fig. 7). DNA sequencing verified the loss of the splice site and the presence of the in-frame stop codon in exon 6 in all 20 individuals examined (data not shown).


The human L-threonine 3-dehydrogenase gene is an expressed pseudogene.

Edgar AJ - BMC Genet. (2002)

Amplicons from 3 individuals for the exon 6 splice acceptor site were digested with the restriction enzyme Hsp92II. All amplicons were digested showing loss of the splice site. Undigested samples, UD and digested samples, D.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC131051&req=5

Figure 7: Amplicons from 3 individuals for the exon 6 splice acceptor site were digested with the restriction enzyme Hsp92II. All amplicons were digested showing loss of the splice site. Undigested samples, UD and digested samples, D.
Mentions: Amplicons from the exon 6 splice acceptor site from 3 individuals were digested with the restriction enzyme Hsp92II. If the acceptor splice site was not present (CATG^g rather than CATAg) the 207 bp amplicon was digested to produce restriction fragments of 112 and 95 bp. Three individuals examined had lost the splice site (Fig. 7). DNA sequencing verified the loss of the splice site and the presence of the in-frame stop codon in exon 6 in all 20 individuals examined (data not shown).

Bottom Line: These truncated proteins are the result of 3 mutations within the gene.There is a SNP, A to G, present in the genomic DNA sequence of some individuals which results in the loss of the acceptor splice site preceding exon 4.The acceptor splice site preceding exon 6 was lost in all 23 individuals genotyped and there is an in-frame stop codon in exon 6 (CGA to TGA) resulting in arginine-214 being replaced by a stop codon.

View Article: PubMed Central - HTML - PubMed

Affiliation: Tissue Engineering & Regenerative Medicine Centre, Division of Investigative Science, Faculty of Medicine, Imperial College of Science, Technology and Medicine, Chelsea & Westminster Hospital, London, United Kingdom. alasdair.edgar@ic.ac.uk

ABSTRACT

Background: L-threonine is an indispensable amino acid. One of the major L-threonine degradation pathways is the conversion of L-threonine via 2-amino-3-ketobutyrate to glycine. L-threonine dehydrogenase (EC 1.1.1.103) is the first enzyme in the pathway and catalyses the reaction: L-threonine + NAD+ = 2-amino-3-ketobutyrate + NADH. The murine and porcine L-threonine dehydrogenase genes (TDH) have been identified previously, but the human gene has not been identified.

Results: The human TDH gene is located at 8p23-22 and has 8 exons spanning 10 kb that would have been expected to encode a 369 residue ORF. However, 2 cDNA TDH transcripts encode truncated proteins of 157 and 230 residues. These truncated proteins are the result of 3 mutations within the gene. There is a SNP, A to G, present in the genomic DNA sequence of some individuals which results in the loss of the acceptor splice site preceding exon 4. The acceptor splice site preceding exon 6 was lost in all 23 individuals genotyped and there is an in-frame stop codon in exon 6 (CGA to TGA) resulting in arginine-214 being replaced by a stop codon. These truncated proteins would be non-functional since they have lost part of the NAD+ binding motif and the COOH terminal domain that is thought to be involved in binding L-threonine. TDH mRNA was present in all tissues examined.

Conclusions: The human L-threonine 3-dehydrogenase gene is an expressed pseudogene having lost the splice acceptor site preceding exon 6 and codon arginine-214 (CGA) is mutated to a stop codon (TGA).

Show MeSH