Discovery of Cell-Permeable Inhibitors That Target the BRCT Domain of BRCA1 Protein by Using a Small-Molecule Microarray

Single-Vehicular Delivery of Antagomir and Small Molecules to Inhibit miR-122 Function in Hepatocellular Carcinoma Cells by using "Smart" Mesoporous Silica Nanoparticles

MicroRNAs (miRNAs) regulate a variety of biological processes. The liver-specific, highly abundant miR-122 is implicated in many human diseases including cancer. Its inhibition has been found to result in a dramatic loss in the ability of Hepatitis C virus (HCV) to infect host cells. Both antisense technology and small molecules have been used to independently inhibit endogenous miR-122 function, but not in combination. Intracellular stability, efficient delivery, hydrophobicity, and controlled release are some of the current challenges associated with these novel therapeutic methods. Reported herein is the first single-vehicular system, based on mesoporous silica nanoparticles (MSNs), for simultaneous cellular delivery of miR-122 antagomir and small molecule inhibitors. The controlled release of both types of inhibitors depends on the expression levels of endogenous miR-122, thus enabling these drug-loaded MSNs to achieve combination inhibition of its targeted mRNAs in Huh7 cells.

A small-molecule protein-protein interaction inhibitor of PARP1 that targets its BRCT domain

Poly(ADP-ribose)polymerase-1 (PARP1) is a BRCT-containing enzyme (BRCT = BRCA1 C-terminus) mainly involved in DNA repair and damage response and a validated target for cancer treatment. Small-molecule inhibitors that target the PARP1 catalytic domain have been actively pursued as anticancer drugs, but are potentially problematic owing to a lack of selectivity. Compounds that are capable of disrupting protein-protein interactions of PARP1 provide an alternative by inhibiting its activities with improved selectivity profiles. Herein, by establishing a high-throughput microplate-based assay suitable for screening potential PPI inhibitors of the PARP1 BRCT domain, we have discovered that (±)-gossypol, a natural product with a number of known biological activities, possesses novel PARP1 inhibitory activity both in vitro and in cancer cells and presumably acts through disruption of protein-protein interactions. As the first known cell-permeable small-molecule PPI inhibitor of PAPR1, we further established that (-)-gossypol was likely the causative agent of PARP1 inhibition by promoting the formation of a 1:2 compound/PARP1 complex by reversible formation of a covalent imine linkage.

EMBO conference series: Chemical Biology 2014

Around 300 people from 18 countries took part in the fourth biennial Chemical Biology conference at The European Molecular Biology Laboratory (EMBL) in Heidelberg, from August 20 to 23, 2014. Many advances in the field of chemical biology were presented in talks and poster sessions. Picture: Petra Riedinger (EMBL).