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Phosphorothioate oligodeoxyribonucleotides dissociate from cationic lipids before entering the nucleus
E G Marcusson1, B Bhat, M Manoharan
1Isis Pharmaceuticals, 2292 Faraday Avenue, Carlsbad, CA 92008, USA.
Nucleic Acids Research
|June 6, 1998
Summary
Cationic lipids enhance cellular uptake of antisense oligonucleotides, but must dissociate for nuclear entry and gene silencing. This dissociation is crucial for effective mRNA degradation and therapeutic potential.
Area of Science:
- Molecular Biology
- Gene Expression Regulation
- Drug Delivery Systems
Background:
- Antisense oligonucleotides (ASOs) are potent gene expression inhibitors.
- Cationic lipids improve ASO cellular uptake and nuclear accumulation in vitro.
- Understanding the intracellular fate of ASO-lipid complexes is key to optimizing their efficacy.
Purpose of the Study:
- To investigate the intracellular fate of oligonucleotide/cationic lipid complexes.
- To determine the role of cationic lipids in ASO delivery and nuclear accumulation.
- To correlate ASO localization with protein kinase C-alpha mRNA reduction.
Main Methods:
- Utilized fluorescently labeled lipids and oligonucleotides targeting protein kinase C-alpha mRNA.
- Tracked the intracellular localization of ASO-lipid complexes over time using microscopy.
- Monitored protein kinase C-alpha mRNA levels and cleavage products.
Main Results:
- Lipids and oligonucleotides initially co-localized on the cell surface and in cytoplasmic puncta.
- Oligonucleotides accumulated in the nucleus at later time points, while lipids remained cytoplasmic.
- Nuclear entry of oligonucleotides preceded protein kinase C-alpha mRNA decline and RNase H-mediated cleavage.
Conclusions:
- Cationic lipids facilitate ASO cellular uptake but do not enter the nucleus with the ASO.
- Complex dissociation is required for ASO nuclear accumulation and subsequent mRNA degradation.
- This finding is critical for the rational design of ASO-based therapeutics.