Abstract: The present invention provides a method of covalently joining a DNA strand to an RNA strand, a method of tagging a 5? end of an RNA molecule, a DNA-RNA molecule which has been joined in vitro by the use of a topoisomerase, a method of tagging a 5? end of an mRNA, and a method of isolating and cloning full-length gene sequences using capped mRNA after subtraction of non-capped RNA.

Abstract: The present invention provides a method of covalently joining a DNA strand to an RNA strand, a method of tagging a 5? end of an RNA molecule, a DNA-RNA molecule which has been joined in vitro by the use of a topoisomerase, a method of tagging a 5? end of an mRNA, and a method of isolating and cloning full-length gene sequences using capped mRNA after subtraction of non-capped RNA.

Abstract: Methods of using microarrays to simplify analysis and characterization of genes and their function are provided. Such methods can be used to identify and characterize antibodies having binding affinity for a specific target antigen. A method of determining gene expression at the protein level by contacting an array of characterized or uncharacterized antibodies on a solid surface with one or more proteins and identifying the antibodies to which said protein(s) binds also is provided. This method can be used to compare the protein expression in two different populations of cells, such as normal cells and cancer cells or resting cells and stimulated cells. In addition, a method of determining gene expression at the protein level by contacting a microarray of nucleic acid samples derived from a variety of different sources with one or more nucleic acid probes then identifying the sample or samples to which the probe binds is provided.

Abstract: 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 intermediate has one or more 5? single-strand tails; and (b) adding to the topoisomerase-DNA intermediate an acceptor RNA strand complementary to the 5? single-strand tail under conditions permitting a ligation of the covalently bound DNA strand of the topoisomerase-DNA intermediate to the RNA acceptor strand and dissociation of the topoisomerase, thereby covalently joining the DNA strand to the RNA strand. The present invention also provides a method of tagging a 5? end of an RNA molecule. The present invention further provides a DNA-RNA molecule which has been joined in vitro by the use of a topoisomerase. The present invention also provides a method of tagging a 5? end of an mRNA.

Abstract: 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 intermediate has one or more 5? single-strand tails; and (b) adding to the topoisomerase-DNA intermediate an acceptor RNA strand complementary to the 5? single-strand tail under conditions permitting a ligation of the covalently bound DNA strand of the topoisomerase-DNA intermediate to the RNA acceptor strand and dissociation of the topoisomerase, thereby covalently joining the DNA strand to the RNA strand. The present invention also provides a method of tagging a 5? end of an RNA molecule. The present invention further provides a DNA-RNA molecule which has been joined in vitro by the use of a topoisomerase. The present invention also provides a method of tagging a 5? end of an mRNA.

Abstract: 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 intermediate has one or more 5′ single-strand tails; and (b) adding to the topoisomerase-DNA intermediate an acceptor RNA strand complementary to the 5′ single-strand tail under conditions permitting a ligation of the covalently bound DNA strand of the topoisomerase-DNA intermediate to the RNA acceptor strand and dissociation of the topoisomerase, thereby covalently joining the DNA strand to the RNA strand. The present invention also provides a method of tagging a 5′ end of an RNA molecule. The present invention further provides a DNA-RNA molecule which has been joined in vitro by the use of a topoisomerase. The present invention also provides a method of tagging a 5′ end of an mRNA.