The present invention provides a method of covalently joining a DNA strand to an RNA strand comprising (a) forming a topoisomerase-DNA intermediate by incubating a DNA cleavage substrate comprising a topoisomerase cleavage site with a topoisomerase specific for that site, wherein the topoisomerase-DNA...http://www.google.de/patents/US7662556?utm_source=gb-gplus-sharePatent US7662556 - Covalent joining of DNA to RNA by vaccinia topoisomerase and uses thereof
