Development of Bioreduction Labile Protecting Groups for the 2'-Hydroxyl Group of RNA

Development of 3'-Deoxy-3',4'-didehydro-nucleoside Prodrug Inhibitors of West Nile and Zika Viruses

The antiviral enzyme viperin catalyzes the formation of 3'-deoxy-3',4'-didehydro-cytidine-5'-triphosphate (ddhCTP). ddhCTP is incorporated into viral genomes and terminates genomic replication to confer broad-spectrum antiviral effects. We have previously utilized phosphoramidate pronucleotide (ProTide) technology to enable metabolic production of ddhCTP in cells from an exogenously dosed 3'-deoxy-3',4'-didehydro-cytidine ProTide, which confers inhibitory activity against West Nile virus (WNV) and Zika virus (ZIKV). Herein, we synthesized 3'-deoxy-3',4'-didehydro-nucleosides containing all native nucleobases (thymine, uracil, adenine, guanine, and hypoxanthine), elaborated each to a ProTide, and measured their activity for controlling WNV and ZIKV infection. In comparison to the ddhC ProTide, we found that the ProTides of 3'-deoxy-3',4'-didehydro-guanosine and 3'-deoxy-3',4'-didehydro-adenosine possess 2- and 4-fold greater antiviral effects against ZIKV, respectively. Collectively, this work advances the development of 3'-deoxy-3',4'-didehydro nucleosides as promising compounds for further development into broad-spectrum antiviral agents.

Multiplex enzymatic synthesis of DNA with single-base resolution

Enzymatic DNA synthesis (EDS) is a promising benchtop and user-friendly method of nucleic acid synthesis that, instead of solvents and phosphoramidites, uses mild aqueous conditions and enzymes. For applications such as protein engineering and spatial transcriptomics that require either oligo pools or arrays with high sequence diversity, the EDS method needs to be adapted and certain steps in the synthesis process spatially decoupled. Here, we have used a synthesis cycle comprising a first step of site-specific silicon microelectromechanical system inkjet dispensing of terminal deoxynucleotidyl transferase enzyme and 3' blocked nucleotide, and a second step of bulk slide washing to remove the 3' blocking group. By repeating the cycle on a substrate with an immobilized DNA primer, we show that microscale spatial control of nucleic acid sequence and length is possible, which, here, are assayed by hybridization and gel electrophoresis. This work is distinctive for enzymatically synthesizing DNA in a highly parallel manner with single base control.

A Bioreductive Protecting Group for RNA Synthesis

This protocol describes a method for the preparation of ribonucleoside phosphoramidite bearing a bioreductive protecting group on the 2'-OH group and its application in the synthesis of bioreduction-responsive oligonucleotides. The protecting group used in this method consists of the modified 4-nitrobenzyl skeleton, which has gem-dimethyl groups at benzylic positions to enable deprotection under physiological conditions. Applying the synthesized ribonucleoside phosphoramidite to solid-phase synthesis of oligonucleotides, a 2'-O-protected oligonucleotide was obtained without any undesirable cleavages under standard oligonucleotide synthesis conditions. The 2'-O-protected oligonucleotide was then treated with a combination of nitroreductase (Escherichia coli) and NADH as a bioreduction system for cleavage of the 2'-O-protecting group. After reduction of the nitro group, the protecting group was deprotected in a time-dependent manner. Thus, this protection technology is a potential new tool for production of reduction-responsive RNA-based materials that can be used in life and medical sciences. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Synthesis of ribonucleoside phosphoramidite bearing a bioreductive protecting group Basic Protocol 2: Synthesis of 2'-O-protected oligonucleotides and their deprotection properties under bioreduction.