Identification of Bioactive SNM1A Inhibitors

Abstract

SNM1A is a nuclease required to repair DNA interstrand cross-links (ICLs) caused by some anticancer compounds, including cisplatin. Unlike other nucleases involved in ICL repair, SNM1A is not needed to restore other forms of DNA damage. As such, SNM1A is an attractive target for selectively increasing the efficacy of ICL-based chemotherapy. Using a fluorescence-based exonuclease assay, we screened a bioactive library of compounds for inhibition of SNM1A. Of the 52 compounds initially identified as hits, 22 compounds showed dose–response inhibition of SNM1A. An orthogonal gel-based assay further confirmed nine small molecules as SNM1A nuclease activity inhibitors with IC 50 values in the mid-nanomolar to low micromolar range. Finally, three compounds showed no toxicity at concentrations able to significantly potentiate the cytotoxicity of cisplatin. These compounds represent potential leads for further optimization to sensitize cells toward chemotherapeutic agents inducing ICL damage.

5’‐Phosphorylation Increases the Efficacy of Nucleoside Inhibitors of the DNA Repair Enzyme SNM1A

“…A high throughput screening of a library of bioactive compounds identified several other SNM1A inhibitors, which have an unclear mechanism of action. [14] The development of substrate-mimic inhibitors for SNM1A facilitates the use of rational design to achieve improvements in efficacy, and has shown promising initial results. Substrate-mimic inhibitors are modified nucleosides, appended with a zinc-binding group (ZBG) to enhance binding to the active site.…”

High-Throughput Exonuclease Assay Based on the Fluorescent Base Analogue 2-Aminopurine

“…The intercalating dye-based assay furthermore requires processive exonuclease activity, as the removal of a single nucleotide will not suffice to change the fluorescent signal (Figure S2). Finally, fluorescent dyes coupled to the end of the DNA substrate 6 or fluorescent dye-quencher pairs have also been used, 7 but here, the presence of a bulky chemical group may interfere with enzymatic activity.…”

Two‐Step Validation Approach for Tools To Study the DNA Repair Enzyme SNM1A

“…[8] New, facile synthetic and screening methodologies are therefore required to rapidly evaluate the efficiency of substrate binding and to access non-native SNM1A substrates. Although screens of bioactive molecules have previously succeeded in identifying several inhibitors of SNM1A, [6,10] there is currently no screening method focused solely on the identification of metalbinding groups, which have been demonstrated as being key for targeting SNM1A. [7][8]11] Fragment-based screening approaches evaluate the ability of low-molecular-weight molecules to exert a desired biological action.…”