Ligation-mediated PCR technique.

Human genomic DNA was isolated. A restriction enzyme digest (↓) was performed. Fragments containing LTR-genomic DNA junctions were marked with a biotinylated LTR-specific primer (GSP1-bio) and enriched by streptavidin-coated paramagnetic beads. Other DNA fragments were flushed away. An adapter-oligo-cassette was ligated to flanking DNA. Solid-phase nested PCR was performed (AP1/AP2, adapter-specific primers; GSP1/GSP5, LTR-specific primers). PCR bands were excised after gel electrophoresis and separately cloned, and clones with different insert lengths were sequenced.