Truncation is a process of shortening something by removing part of it. In biology, truncation is the removal of the N- or C-terminal portion of a protein by proteolysis or structural gene manipulation, or premature termination of protein elongation due to the presence of a stop codon in its structural gene as a result of a nonsense mutation. Genetic variants that result in a shorter version of the protein being produced are also known as truncations. Methods based on DNA shuffling have been used to modify genes, genomes and proteins in both prokaryotic and eukaryotic organisms.
Transposons are particularly useful for this purpose, as they can integrate efficiently and relatively randomly into target DNA. However, the efficiency and degree of randomness of integration vary considerably between different transposons. The Protein Truncation Test (PTT) is a simple and rapid method for detecting biologically relevant genetic mutations. The method is based on the size analysis of the products resulting from in vitro transcription and translation.
Proteins of lower mass than the expected full-length protein represent translation products derived from truncating, frameshift or termination mutations in the analyzed gene. Conventional PTT has low sensitivity, so it can only detect mutations in samples with a relatively high number of copies of mutated genes. To overcome this limitation, modifications such as gene capture and digital TTP have been developed to reduce the detection limit and allow the use of TTP in the detection of mutations in body fluids. Additionally, fluorescent labels or labeled epitopes can be used to detect non-radioactive translation products.
When several epitopes are used in different reading frames, the mutation detection spectrum can be expanded to all possible frameshift mutations. These modifications transform PTT into a powerful non-radioactive technique for detecting mutations with high sensitivity. Truncation can also be applied to physical things, such as tree trunks which can be cut to the stump. In addition, truncation libraries expressing high quality proteins can be created using in vitro Mu shuffling combined with efficient selection schemes during DNA manipulation steps. Truncation is an important tool for genetic engineering applications, as it allows for the creation of large groups of insertion mutants in a single series of simple reactions.
It is also useful for detecting mutations with high sensitivity, making it an invaluable tool for molecular and genomic studies.
