2',3'-Dideoxy-3'-thionucleoside triphosphates: syntheses and polymerase substrate activities

Area of Science:

• Biochemistry
• Molecular Biology
• Enzymology

Background:

• DNA polymerases are crucial enzymes for DNA replication and repair.
• Nucleoside analogs are widely used in antiviral and anticancer therapies.
• Understanding polymerase substrate specificity is key to drug development.

Purpose of the Study:

• To investigate the substrate potential of 2',3'-dideoxy-3'-thio-nucleosides (ddtNTPs) for a modified Deep Vent DNA polymerase.
• To explore the mechanism of ddtNTP incorporation and subsequent DNA chain elongation.
• To assess the feasibility of using thiol nucleophiles in DNA synthesis.

Main Methods:

• Enzymatic assays using Y410F mutant Deep Vent (exo-) DNA polymerase.
• Synthesis of four ddtNTP analogs (cytosine, thymine, adenine, guanine).
• Analysis of DNA synthesis products using gel electrophoresis and sequencing.

Main Results:

• All four synthesized ddtNTPs were successfully incorporated by the Y410F Deep Vent polymerase.
• Further DNA elongation occurred via attack of the 3'-thiol on the 5'-triphosphate.
• Demonstrated that a thiol nucleophile can participate in phosphate anhydride electrophile reactions during DNA synthesis.

Conclusions:

• The Y410F Deep Vent DNA polymerase can utilize ddtNTPs as substrates, leading to novel DNA chain elongation.
• The findings challenge previous assumptions about the limitations of thiol nucleophiles in DNA synthesis.
• Suggests potential for developing new DNA modifying agents and understanding polymerase mechanisms.