Covalently linked sequencing primer linkers (splinkers) for sequence analysis of restriction fragments

A new method for direct sequence analysis of DNA restriction fragments uses synthetic covalently linked complementary oligodeoxynucleotides, as universal sequencing primer linkers (splinkers). These splinkers were designed to contain an inverted repeat sequence which forms a double-stranded hairpin structure with a known restriction site. The splinkers were characterized by their ability to be self-ligating (dimerized) and by their restriction digest product analysis of both the monomer and dimer. They can also be ligated to dephosphorylated DNA restriction fragments which contain the appropriate end. This was evidenced by mobility shifts of the splinker-ligated restriction fragments. The splinker-ligated restriction fragments, after denaturation, form a single-stranded DNA template containing an inverted repeat sequence (from splinker) at one terminus. The splinker is thus suitably oriented and serves as a primer for dideoxy nucleotide (nt) sequencing catalyzed by either Klenow fragment of Escherichia coli DNA polymerase I or avian myeloblastosis virus reverse transcriptase. As demonstrated for both pBR322 and phi X174, release of the primer extension strand by digestion at the splinker restriction site results in a ladder of labelled fragments which corresponds to a unique nt sequence.