• Biomedical Science Letters
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• v.6 no.1
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• pp.73-82
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• 2000

Blunt-end DNA fragments can be inserted in two different orientations. Conventionally, their directions are determined by restriction enzyme digestion or by DNA sequencing, however, these methods are often limited in their use due to the lack of appropriate enzyme sites or large sample numbers, respectively. In the present study, a novel strategy and the corresponding protocol for the simple determination of insert orientation is introduced. Using conventional sequencing primers and PCR primers that have been used for amplification of the insert, single clones, which have inserted the fragment in the desired orientation, were easily identified by this PCR-based method. The fidelity of this system was confirmed by cloning of a tar urocortin cDNA, which is a recently discovered neuropeptide. Recombinant clones identified by this method were further shown to be fully functional, and using these, for the first time, urocortin was recombinantly expressed in eukaryotic cells.