Abstract: The present invention provides methods and compositions that enable tagging and amplification of targeted RNA molecules. A targeted RNA molecule is any non-polyadenylated RNA molecule including, for example, miRNA, siRNA, rRNA, tRNA, synthetic RNA, or non-polyadenylated mRNA such as mRNA from bacteria. In certain aspects, the invention provides methods and compositions for the genome-wide expression analysis of bacterial genes. Significantly, the methods enable genome-wide expression analysis in circumstances where bacterial numbers were previously too low to purify adequate amounts of RNA for DNA microarray analysis or other applications. Such methods are particularly useful for the study of bacterial gene expression during host-cell infection. The invention also provides kits for tagging and amplifying targeted RNA molecules.

Abstract: The present invention concerns a system for isolating, depleting, or separating a targeted nucleic acid, such as rRNA, from a sample comprising targeted and nontargeted nucleic acids. It effects a way of enriching for nontargeted nucleic acids, such as mRNAs. The invention further concerns methods of implementing the system and kits for implementing the system, which involves at least one bridging nucleic acid comprising 1) a targeting region complementary to a region on the targeted nucleic acid and 2) a bridging region complementary to the capture region of a capture nucleic acid that comprises a nonreactant structure. The nonreactant structure can be used to isolate the hybridizing molecules after incubation under conditions that allows hybridization.