TBX1: Difference between revisions

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The -39C → T mutant change affects the secondary structure of the mRNA. It lies outside of the 129 bp 5'-UTR, which ordinarily contains 76% GC content. Molecular modelling predicts a stable secondary structure for the wild-type TBX1, but the presence of T instead of C at -39 reduces the stability of this fold, reuslting in a different optimal folding from that of the wild type. Using luciferase as a marker, experiments showed that this mutation greatly increases the amount of TBX1 present in the cell by about 2-fold. This results in the phenotype caused by overexpression of TBX1.

==tbx1 1223delC==

The F148Y and G310S equivalent mutations in mice are still able to activate transcription at nearly the same capacity as the wild-type Tbx1 using a luciferase reporter construct. However, the Tbx1delC mutant has almost the same activation activity as the control used. When the Tbx1delC mutant was examined for subcellular localisation, it was found that it was localised almost entirely to the cytoplasm. The Tbx1delC mutation results in a frameshift of 51 codons before a premature stop codon, with 86 residues missing from Tbx1delC which are normally found in wild-type Tbx1 Deletion of 31 residues from the C-terminus of wild-type Tbx1 results in a truncated protein which does localise correctly to the nucleus. However, deletion of 86 residues results in a truncated protein which localises to the cytoplasm. Thus, the idea of an NLS present in the C-terminus of Tbx1 is likely.

This NLS has been tracked down to a 12-residue motif present in the C-terminus by a series of further deletions fused to GFP and β-galactosidase. This fragment spans residues 415-426 inclusive. There is no significant homology to previously identified NLS sequence. A proline-rich sequence containing the motif BPYPXPB, where B is a basic amino acid, is a conserved sequence throughout Tbx1, Tbx10 and Brachyury. Mutations of R417A and Y421 of the wild-type protein combined resulted in a reduced nuclear localisation signal. The proline residues, although conserved, did not produce this effect.

Tbx1delC also results in the disruption of a transactivation domain.

==References==

* Human Molecular Genetics (2005) 14:7

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 The -39C → T mutant change affects the secondary structure of the mRNA.  It lies outside of the 129 bp 5'-UTR, which ordinarily contains 76% GC content.  Molecular modelling predicts a stable secondary structure for the wild-type TBX1, but the presence of T instead of C at -39 reduces the stability of this fold, reuslting in a different optimal folding from that of the wild type.  Using luciferase as a marker, experiments showed that this mutation greatly increases the amount of TBX1 present in the cell by about 2-fold.  This results in the phenotype caused by overexpression of TBX1.
+==tbx1 1223delC==
+The F148Y and G310S equivalent mutations in mice are still able to activate transcription at nearly the same capacity as the wild-type Tbx1 using a luciferase reporter construct.  However, the Tbx1delC  mutant has almost the same activation activity as the control used.  When the Tbx1delC mutant was examined for subcellular localisation, it was found that it was localised almost entirely to the cytoplasm.  The Tbx1delC mutation results in a frameshift of 51 codons before a premature stop codon, with 86 residues missing from Tbx1delC which are normally found in wild-type Tbx1  Deletion of 31 residues from the C-terminus of wild-type Tbx1 results in a truncated protein which does localise correctly to the nucleus.  However, deletion of 86 residues results in a truncated protein which localises to the cytoplasm.  Thus, the idea of an NLS present in the C-terminus of Tbx1 is likely.
+This NLS has been tracked down to a 12-residue motif present in the C-terminus by a series of further deletions fused to GFP and β-galactosidase.  This fragment spans residues 415-426 inclusive.  There is no significant homology to previously identified NLS sequence.  A proline-rich sequence containing the motif BPYPXPB, where B is a basic amino acid, is a conserved sequence throughout Tbx1, Tbx10 and Brachyury.  Mutations of R417A and Y421 of the wild-type protein combined resulted in a reduced nuclear localisation signal.  The proline residues, although conserved, did not produce this effect.
+Tbx1delC also results in the disruption of a transactivation domain.
+==References==
+* Human Molecular Genetics (2005) 14:7