The miRNA strand of our mimics is made of unmodified RNA to provide as accurate miRNA mimicry as possible. The sequence and LNA spiking pattern of the two complementary passenger strands have been carefully designed to optimize efficient incorporation of the miRNA (guide) strand into RISC (see figure Silencing of miRNA reporters using mimics
for examples of the high potency of these LNA mimics).
No miRNA star-like activity from the passenger strand
miRCURY LNA miRNA Mimics have an innovative design, which includes two short LNA-enhanced complimentary strands that prevent any miRNA-like activity associated with the passenger strands (see figure The distinct RNA triplex design ensures completely specific miRNA mimicry
). This guarantees that phenotypes observed using these mimics are due to increased activity of the mimicked miRNA.
Fluorescently labeled miRNA mimics
Fluorescently labeled miRNA mimics can be useful to assess transfection efficiency. However, addition of fluorescent labels to the 5’ or 3’ end of the miRNA strand completely removes activity of miRNA mimics. In contrast, fluorophores at the 5’ end of the passenger strand are tolerated and have no adverse effects on the resulting mRNA activity (see figures Fluorescently labeled miRNA mimics
and Biotinylated miRCURY LNA miRNA mimics
). Because the fluorophore is attached to the passenger strand, the fluorescent signal does not report on the intracellular localization of the miRNA strand that is loaded into RISC and is only useful for monitoring transfection efficiency (see figure Silencing of miRNA reporter assays with fluorescently labeled miRCURY LNA miRNA Mimics
Biotinylated miRNA mimics
Modification of the 5’ and 3’ ends of the miRNA strand in mimics is generally not well tolerated at all. However, we have observed that potent miRNA activity is achievable with biotinylated mimics, although they are significantly less potent than non-modified mimics, presumably due to less efficient loading into RISC. Nevertheless, the possibility that biotin modification of the guide strand creates a bias for incorporation of the passenger strand cannot be excluded. It is therefore important to use modified mimics that ensure that only the miRNA strand is chosen by RISC. The special triple RNA strand design of miRCURY LNA miRNA mimics ensures complete miRNA strand specificity, since the passenger strand is split into two LNA-modified RNA strands (see figures The distinct RNA triplex design ensures completely specific miRNA mimicry
and Silencing of miRNA reporter assays with biotinylated miRCURY LNA miRNA Mimics