An HIV reverse transcriptase-selective nucleoside chain terminator.

Area of Science:

• Medicinal Chemistry
• Organic Synthesis
• Molecular Biology

Background:

• Development of novel nucleoside analogues is crucial for antiviral therapies.
• Understanding polymerase selectivity is key to designing effective drugs.
• The O2-carbonyl group's role in nucleoside interactions is not fully understood.

Purpose of the Study:

• To synthesize a novel 2',3'-dideoxynucleoside cytidine analogue lacking the O2-carbonyl.
• To evaluate the substrate potential of the analogue's triphosphate form (ddNTP) with various DNA polymerases.
• To investigate the impact of the O2-carbonyl absence on polymerase recognition and activity.

Main Methods:

• Synthesis of the 2-pyridone C-nucleoside analogue using Heck-type coupling.
• Conversion of the dideoxynucleoside to its 5'-triphosphate form.
• Enzymatic assays using HIV reverse transcriptase, calf thymus DNA polymerase alpha, human DNA polymerase beta, and human mitochondrial DNA polymerase.

Main Results:

• The synthesis yielded the target cytidine analogue in 60% overall yield.
• The analogue ddNTP was a reasonable substrate for HIV reverse transcriptase with a dG template.
• The analogue was not a substrate for calf thymus DNA polymerase alpha or human DNA polymerase beta, and a poor substrate for human mitochondrial DNA polymerase.

Conclusions:

• The absence of the O2-carbonyl in the cytidine analogue significantly alters its interaction with DNA polymerases.
• This modification leads to polymerase selectivity, potentially due to destabilized base pairing or loss of critical polymerase contacts.
• The findings provide insights into the structural requirements for polymerase substrate recognition and could inform future antiviral drug design.