Ligation of a primer at a mutation: a method to detect low level mutations in DNA.
Detection of low frequency mutations following exposure to mutagens or during the early stages of cancer development is instrumental for risk assessment and molecular diagnosis. We present a sensitive new method to detect trace levels of DNA mutations induced within a large excess of wild-type sequences. The method is based on mutation-induced generation of new restriction enzyme recognition sites. A DNA sequence is amplified from genomic DNA or cDNA using a high fidelity polymerase. The purified PCR product is digested with a restriction enzyme that recognizes the newly generated restriction site, partially dephosphorylated and ligated with an oligonucleotide at the position of the mutation. The ligated oligonucleotide is then utilized in two rounds of PCR to amplify the mutated DNA but not the wild-type allele that contains no restriction site. An A-->T polymorphism in mRNA (tenascin gene, A(2366)-->T, Asn-->Ile) and a G-->A polymorphism in genomic DNA (Ku gene, G(74582)-->A, Val-->Ile), both of which generate a restriction site for the enzyme SAU3A1, demonstrate the application. Eleven patient samples pre-characterized for the G(74582)-->A polymorphism in the repair gene Ku are used to demonstrate the reliability of this approach. This technique quantitatively detects the Ku G-->A polymorphism at a mutant frequency of 1.6x10(-6) relative to the wild-type allele. Mutations in p53 that are frequently induced by mutagens can readily be detected using the present method. As an example, using a second enzyme BbvI, a mutation frequently encountered in human cancers (G(14154)-->A mutation, p53 codon 245, Arg-->Gln) was detected in patient samples. The process does not require radioactivity, utilizes established procedures and overcomes several factors known to produce false positives in RFLP-based assays. The present amplification via primer ligation at the mutation (APRIL-ATM) has potential applications in the detection of mutagen-generated genetic alterations, early detection of tumor marker mutations in bodily discharges and the diagnosis of minimal residual disease.
Kaur
Manjit
M
Department of Radiation Oncology, Dana Farber Cancer Institute, Harvard Medical School, Boston, MA, USA.
Zhang
Yuzhi
Y
Liu
Wei-Hua
WH
Tetradis
Sotirios
S
Price
Brendan D
BD
Makrigiorgos
G Mike
GM
D000230:Adenocarcinoma / Q000235:genetics; D034961:Antigens, Nuclear / Q000235:genetics; D001859:Bone Neoplasms / Q000235:genetics; D004265:DNA Helicases; D011088:DNA Ligases / Q000378:metabolism; D004252:DNA Mutational Analysis / Q000379:methods*; D017931:DNA Primers / Q000737:chemistry; D004273:DNA, Neoplasm / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D016158:Genes, p53 / Q000235:genetics*; D006801:Humans; D000072200:Ku Autoantigen; D008175:Lung Neoplasms / Q000235:genetics; D009154:Mutation; D012516:Osteosarcoma / Q000235:genetics; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012333:RNA, Messenger / Q000235:genetics; D019063:Tenascin / Q000235:genetics*; D014407:Tumor Cells, Cultured
D034961:Antigens, Nuclear; D017931:DNA Primers; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D019063:Tenascin; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen; D011088:DNA Ligases