The present invention provides a novel method for ligation of
oligonucleotides containing 5'-phosphorothioates on complementary
templates by the action of DNA ligases. This reaction is readily applied
to the synthesis of a single stranded circular DNA containing a
phosphorothioate linkage at the site of ligation junction. The efficiency
of 5'-phosphorothioate directed ligation reaction by ATP dependent DNA
ligase reaction is similar to conventional 5'-phosphate ligation. The
utility of enzymatic ligation in probing specific sequences of DNA is also
described. The present invention also provides a novel non-enzymatic
ligation of 5'-phosphorothioates that has been applied to the synthesis of
single strand phosphorothioate and phosphate circular DNA. A process for
detecting the presence of a mismatch in an otherwise complementary pair of
oligonucleotides is disclosed using an enzyme-based technique which shows
the presence of a mismatch by failing to form a ligated single stranded
DNA circle that can optionally be amplified using standard methods of
rolling circle amplification.
