A fragment-based approach to target Ube2T, the ubiquitin-conjugating enzyme of the Fanconi anemia pathway

Venue: Edificio Povo 2, via Sommarive nr. 9, Povo (Tn) - Room B105
 At 2:00 p.m.

• Francesca Ester Morreale - School of Life Sciences, MRC PPU Unit, University of Dundee, UK

In recent years, fragment-based drug discovery has emerged as a valid approach for early stage drug development, particularly useful to identify druggable pockets on protein surfaces. Here we report the application of fragment screening to probe the druggability of Ube2T, the ubiquitin-conjugating enzyme involved in the Fanconi anemia DNA repair pathway. Ube2T specifically interacts with FANCL, a monomeric RING E3 ligase, for the strict monoubiquitination of FANCD2. This exclusive E2-E3 pair is the catalytic centre of the Fanconi anemia pathway, which is activated in the presence of DNA interstrand cross-links. We used a combination of biophysical techniques to screen a library of 1200 fragments: we performed a primary screen by differential scanning fluorimetry (DSF) and bio-layer interferometry (BLI) that was followed by validation of preliminary hits through ligand and protein based NMR spectroscopy, and investigation of the exact binding mode through X-ray crystallography. We identified several fragments that bind two distinct pockets on Ube2T surface and are able to reduce FANCD2 monoubiquitination in vitro. The optimisation of such fragments into potent inhibitors can be useful to further investigate the events leading to the activation of the Fanconi anemia pathway, moreover anticancer activity of such compounds can be explored, as modulation of DNA repair is an emerging target for the development of inhibitors of tumour cell growth.