The protein truncation test: A review

Only changes in the DNA sequence manifesting deleterious effects at a funct ional level provide "disease-causing" mutations. Consequently, mutation-sca nning techniques applied on a protein level would be most informative. Howe ver, because of a lack of functional knowledge and powerful methods, most c urrently applied techniques try to resolve mutations at the DNA level. The protein truncation test (PTT) provides a rare exception, targeting mutation s that generate shortened proteins, mainly premature translation terminatio n. PTT has several attractive characteristics, including pinpointing the si te of a mutation, good sensitivity, a low false-positive rate, and, more im portantly the near exclusive highlighting of disease-causing mutations. In addition, PTT facilitated the detection of a new mutation type, i.e,, a seq uence change generating a hypermutable region surfacing in the RNA. The mai n technical problems are related to the fact that PTT generally uses an RNA target, including the difficulties that arise from the potential different ial expression and stability of the transcripts derived from the two allele s present. The PTT has hardly evolved from the method originally described, with multiplexing and N-terminal protein tagging forming the only innovati ng modifications. To implement high-throughput screens using PTT, major imp rovements of the basic procedure will be required. Hum Mutat 14:95-102, 199 9. (C) 1999 Wiley-Liss, Inc.