Restouin, A. | Search bioRxiv

bioRxiv2021

CRCM5484: A BET- BDII Selective Compound With Differential Anti-Leukemic Drug Potentiation

Differentially screening the Fr-PPIChem chemical library on the BET BRD4-BDII versus -BDI bromodomains led to the discovery of a BDII selective tetrahydropyridothienopyrimidinone (THPTP)-based compound. Structure-activity relationship (SAR) and hit-to-lead approaches allowed us to develop CRCM5484, a potent inhibitor of BET proteins with a preferential and 475-fold selectivity for the second bromodomain of the BRD3 protein (BRD3-BDII) over its first bromodomain (BRD3-BDI). Its very low activity was demonstrated in various cell-based assays, corresponding with recent data describing other selective BDII compounds. However, screening on a drug sensitivity and resistance-profiling platform revealed its ability to modulate the anti-leukemic activity in combination with various FDA-approved and/or in-development drugs in a cell- and context-dependent differential manner. Altogether, the results confirm the originality of the THPTP molecular mode of action in the BD cavity and its potential as starting scaffold for the development of potent and selective bromodomain inhibitors.

cancer biology↗

bioRxiv2020

Synergy and allostery in ligand binding by HIV-1 Nef

The Nef protein of human and simian immunodeficiency viruses (HIV and SIV, respectively) boosts viral pathogenicity through its interactions with host cell proteins. Nef has a folded core domain and large flexible regions, each carrying several protein interaction sites. By combining the polyvalency intrinsic to unstructured regions with the binding selectivity and strength of a 3D folded domain, Nef can bind to many different host cell proteins, perturbing their cellular functions. For example, the combination of a linear proline-rich motif and a hydrophobic core domain surface allows Nef to increase affinity and selectivity for particular Src family SH3 domains. Here we investigated whether the interplay between Nefs flexible regions and its core domain can allosterically influence ligand selection. We found that the flexible regions can bind back to the core domain in different ways, producing distinct conformational states that alter the SH3 domain selectivity and availability of Nefs functional motifs. The resulting cross-talk might help synergising certain subsets of ligands while excluding others, promoting functionally coherent Nef-bound protein ensembles. Further, we combined proteomic and bioinformatic analyses to identify human proteins that select SH3 domains in the same way as does Nef. We found that only 2-3% of clones from a whole human fetal library displayed a Nef-like SH3 selectivity. However, in most cases this selectivity appears to be achieved by a canonical linear interaction rather than a Nef-like tertiary interaction. This analysis suggests that Nefs SH3 recognition surface has no (or marginally few) cellular counterparts, validating the Nef tertiary binding surface as a promising unique drug target.

biophysics↗