Nucleic acid amplification with DNA-dependent RNA polymerase activity of RNA replicases

The present invention entails methods, and kits for carrying them out, based on the discovery that an RNA replicase, such as Q beta replicase, has DNA-dependent RNA polymerase ("DDRP") activity with nucleic acid segments, including DNA segments and DNA:RNA chimeric segments, which comprise a 2'-deoxyribonucleotide or an analog thereof and which have sequences of RNAs that are autocatalytically replicatable by the replicase. The discovery of this DDRP activity provides methods of the invention for nucleic acid amplification wherein a nucleic acid, with a DNA segment with the sequence of an RNA that is autocatalytically replicatable by an RNA replicase, is provided as a substrate for the replicase. Assays of the invention include those wherein a nucleic acid analyte is hybridized with one or more nucleic acid probes, which include or are processed to generate a DNA segment which is amplifiable through production from the segment, catalyzed by the DDRP activity of an RNA replicase, of an autocatalytically replicatable RNA, which is autocatalytically replicated to provide an abundance of readily detectable reporter molecules.