The protein truncation test (PTT) is used to identify mutations that result in premature termination of protein translation. PTT detects mutations at the protein rather than the genomic DNA or RNA levels. Initially developed for Duchenne muscular dystrophy (DMD) testing, PTT now is used more widely,50 since protein-truncating mutations are associated with multiple types of hereditary cancer syndromes, including breast, ovarian, and colon.
For PTT, the gene segment of interest is amplified by PCR. The amplicons are used for in vitro transcription and translation in a coupled reaction. The resulting proteins are separated using sodium dodecyl sulfate (SDS) polyacry-lamide gel electrophoresis. The presence of a premature termination codon is indicated by the visualization of a lower-molecular-weight protein band than for the wildtype protein. Relatively large gene fragments (2-4kb) can be analyzed using PTT.
Examples of Applications of PTT
1. Duchenne muscular dystrophy diagnosis
2. BRCA1 and BRCA2 mutation detection51
3. APC mutations in colorectal cancer52
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