Related Experiment Video
Updated: Aug 1, 2026

Nucleoside Triphosphates - From Synthesis to Biochemical Characterization
Published on: April 3, 2014
Cellular pharmacology of phosphorothioate homooligodeoxynucleotides in human cells
1Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06510.
Abstract:
The uptake and distribution of phosphorothioate oligodeoxynucleotides by human cells were studied using 35S-labeled 28-mer phosphorothioate oligodeoxycytidine [S-(dC)28]. Accumulation of intracellular S-(dC)28 was found to be higher in the carcinoma cells (grown in monolayers) than in the leukemia cells (grown in suspension culture). A hepatoma cell line transfected with hepatitis B virus, 2215, was chosen for further studies. The uptake of S-(dC)28 was partially dependent on temperature and energy. The intracellular concentration was significantly higher than that in the medium and the amount accumulated was dependent on the extracellular concentration. It appears that the uptake of S-(dC)28 involves mechanisms of both fluid-phase pinocytosis and adsorptive endocytosis. Neither oligonucleotides nor 5'-phosphorylated nucleotides inhibited S-(dC)28 uptake. Unlike horseradish peroxidase, which was primarily associated with endosomes once it was taken into the cell, S-(dC)28 was found to be present in both nuclear and cytoplasmic fractions. Efflux of S-(dC)28 from the cell was multiphasic; a trapping mechanism that could be due to a potent interaction of S-(dC)28 with cellular proteins was implicated. This trapping mechanism could be responsible for the lack of biological activity such as cytotoxicity and antisense activity of phosphorothioate oligodeoxynucleotides in some human cells.
Related Concept Videos
Phosphodiester Linkages
Phosphodiester bond forms when a phosphoric acid molecule (H3PO4) links with two hydroxyl groups (–OH) of two other molecules, forming two ester bonds. Two water molecules are released in this process. The phosphodiester bond is commonly found in nucleic acids (DNA and RNA) and plays a critical role in their structure and function.
Phosphodiester Bonds Link Nucleotides Together
DNA and RNA are polynucleotides or long chains of nucleotides that are linked together. A nucleotide is...
Phosphorylation
During phosphorylation, protein kinases transfer the terminal phosphate group of ATP to specific amino acid side chains of substrate proteins. Serine, threonine, and tyrosine are the most commonly...
Protein Kinases and Phosphatases
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...
Pharmacogenetics of Drug Targets: β₂-Adrenergic Receptors, Apo E, Thymidylate Synthase
Biosynthesis of Nucleic Acids

