Antisense oligos are short sections of nucleic acids or nucleic acid analogs that can be used to target sites on RNA to alter gene expression, most commonly suppressing gene expression. There are several mechanisms of action that depend on the chemistry of the oligos used. RNase-H competent oligos, such as DNA or phosphorothioate-linked DNA, trigger the action of RNase-H to degrade complementary RNAs to which they bind. RNase-independant oligos, such as Morpholinos, peptide nucleic acids, locked nucleic acids, 2'-O-Me phosphorothioate RNA etc., bind to complementary sites on RNA and act like masking tape, getting in the way of processes. The RNase-independant oligos are used to:
- block translation by blocking the progression of the translation initiation complex to the start codon,
- modify splicing by blocking snRNP binding sites on pre-mRNA,
- block miRNA maturation by invading the mIRNA precursor hairpin and blocking the nucleolytic processing sites,
- block miRNA activity by binding to a guide strand or a microRNA response element on the 3'-UTR of an mRNA,
- block a poly-A tailing signal sequence,
- block a splice regulatory protein binding site,
etc.
Wikipedia has good pages on antisense oligos.