Antisense therapy blocks gene expression at level of:
Antisense strategy modulates gene expression multiple stages RNA metabolism not protein folding secretion downstream. Design involves complementary oligonucleotide binding pre-mRNA sequences within 5 prime splice donor GU branch point adenosine polypyrimidine tract exonic splicing enhancer ESE purine-rich recognized SR proteins altering spliceosome U1 U2 snRNP assembly dictating alternative splicing outcomes enabling exon 7 inclusion SMN2 or exon 51 skipping dystrophin restoring open reading frame disrupted deletion. Binding 5 prime 7-methylguanosine cap AUG start codon context Kozak sequence sterically blocks 40S scanning 80S assembly inhibiting translation initiation complex eIF2 GTP Met tRNA. Some oligos DNA portion recruit RNase H1 endonuclease recognizing DNA-RNA hybrid hydrolyzing RNA strand reducing overall transcription output via premature termination involving XRN2 torpedo model chasing Pol II. Phosphorodiamidate morpholino oligomers act steric hindrance independent RNase H. Thus predominant actions occur transcription elongation splicing regulation translation blockade all upstream post-translational maturation secretion pathways offering reversible suppression without genome alteration suitable therapeutic intervention.
Ref: Nature Rev Drug Disc Antisense Transcription Translation Blockade 2020; FDA Antisense Mechanism Guidance; Alberts RNA Processing Antisense Regulation Chap 8.