Differential Inhibition of APOBEC3 DNA‐Mutator Isozymes by Fluoro‐ and Non‐Fluoro‐Substituted 2′‐Deoxyzebularine Embedded in Single‐Stranded DNA

Abstract

The APOBEC3 (APOBEC3A‐H) enzyme family is part of the human innate immune system that restricts pathogens by scrambling pathogenic single‐stranded DNA (ssDNA) via deamination of cytosines to uracils. However, APOBEC3‐mediated mutagenesis of viral and cancer DNA promotes its evolution, enabling disease progression and development of drug resistance. Therefore, APOBEC3 inhibition offers a new strategy to complement existing anti‐viral and anti‐cancer therapies by making such therapies effective for longer periods of time, thereby preventing the emergence of drug resistance. Here, we have synthesised 2'‐deoxynucleoside forms of several known inhibitors of cytidine deaminase (CDA), incorporated them into oligodeoxynucleotides (oligos) in place of 2'‐deoxycytidine in the preferred substrates of APOBEC3A, APOBEC3B, and APOBEC3G, and evaluated their inhibitory potential against these enzymes. An oligo with 5‐fluoro‐2'‐deoxyzebularine (5FdZ) exhibited a 3.5 times better inhibition constant in comparison with the comparable 2'‐deoxyzebularine (dZ) containing oligo against APOBEC3B. A similar trend of inhibition was observed for wild‐type APOBEC3A. In contrast, use of 5FdZ in an oligo designed for APOBEC3G inhibition resulted in a less potent inhibitor than the dZ‐containing oligo for both APOBEC3GCTD and full‐length wild‐type APOBEC3G.