Recognition of mixed-sequence double-stranded DNA regions using chimeric Invader/LNA probes

Development of robust oligonucleotide-based probe technologies, capable of recognizing specific regions of double-stranded DNA (dsDNA) targets, continues to attract considerable attention due to the promise of tools for modulation of gene expression, diagnostic agents, and new modalities against genetic diseases. Our laboratory pursues the development of various strand-invading probes. These include Invader probes, i.e., double-stranded oligonucleotide probes with one or more +1 interstrand zipper arrangements of intercalator-functionalized nucleotides like 2'-O-(pyren-1-yl)methyl-RNA monomers, and chimeric Invader/γPNA probes, i.e., heteroduplex probes between individual Invader strands and complementary γPNA strands. Here we report on the biophysical properties and dsDNA-recognition characteristics of a new class of chimeric probes-chimeric Invader/LNA probes-which are comprised of densely modified Invader strands and fully modified complementary LNA strands. The chimeric Invader/LNA probes form labile and distorted heteroduplexes, due to an apparent incompatibility between intercalating pyrene moieties and LNA strands. In contrast, the individual Invader and LNA strands form very stable duplexes with complementary DNA, which provides the driving force for near-stoichiometric recognition of model double-stranded DNA targets with single base-pair accuracy. The distinctive properties of chimeric Invader/LNA probes unlock exciting possibilities in molecular biology, and diagnostic and therapeutic fields.