Restriction-site PCR: a direct method of unknown sequence retrieval adjacent to a known locus by using universal primers.

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Abstract
Fast acquisition of unknown nucleotide sequences around a known sequence has important implication in molecular biology, especially in genome mapping. We have developed a method, termed restriction site polymerase chain reaction (RS-PCR), that utilizes specially designed primers that recognize, anneal, and sustain PCR. These primers, termed restriction site oligonucleotides (oligonucleotide primers specific for a given restriction enzyme recognition sequence or RSOs), could be generated corresponding to any restriction enzyme irrespective of the length of the recognition site and used as PCR primers corresponding to the unknown region of a DNA segment. In this method a first round of PCR is carried out in different tubes with a set of RSOs and a primer specific to the known region. A second round of PCR is then performed on the products of the first PCR with the same RSOs and another specific primer internal to the first one. Subsequently, the products of the last round of PCR are transcribed with an appropriate RNA polymerase and sequenced with a reverse transcriptase with an end-labeled specific primer internal to the second specific PCR primer. To demonstrate the applicability of RS-PCR in retrieving unknown sequences around a known sequence, we have used a set of four RSOs and three specific primers representing the known sequence and have successfully obtained hitherto unknown factor IX sequences (12 of 12 times) from three species starting from genomic DNA. The sequences obtained indicate the presence of a conserved stretch of 20 nucleotides in the 3' noncoding region of the factor IX gene.(ABSTRACT TRUNCATED AT 250 WORDS)