RESUMEN
Deubiquitinases are important components of the protein degradation regulatory network. We report the discovery of ML364, a small molecule inhibitor of the deubiquitinase USP2 and its use to interrogate the biology of USP2 and its putative substrate cyclin D1. ML364 has an IC50 of 1.1 µm in a biochemical assay using an internally quenched fluorescent di-ubiquitin substrate. Direct binding of ML364 to USP2 was demonstrated using microscale thermophoresis. ML364 induced an increase in cellular cyclin D1 degradation and caused cell cycle arrest as shown in Western blottings and flow cytometry assays utilizing both Mino and HCT116 cancer cell lines. ML364, and not the inactive analog 2, was antiproliferative in cancer cell lines. Consistent with the role of cyclin D1 in DNA damage response, ML364 also caused a decrease in homologous recombination-mediated DNA repair. These effects by a small molecule inhibitor support a key role for USP2 as a regulator of cell cycle, DNA repair, and tumor cell growth.
Asunto(s)
Puntos de Control del Ciclo Celular/efectos de los fármacos , Neoplasias Colorrectales/metabolismo , Ciclina D1/metabolismo , Endopeptidasas/metabolismo , Linfoma de Células del Manto/tratamiento farmacológico , Proteínas de Neoplasias/antagonistas & inhibidores , Proteínas de Neoplasias/metabolismo , Inhibidores de Proteasas/farmacología , Proteolisis/efectos de los fármacos , Puntos de Control del Ciclo Celular/genética , Línea Celular Tumoral , Neoplasias Colorrectales/genética , Ciclina D1/genética , Daño del ADN , Reparación del ADN , Endopeptidasas/genética , Humanos , Linfoma de Células del Manto/genética , Linfoma de Células del Manto/metabolismo , Proteínas de Neoplasias/genética , Inhibidores de Proteasas/química , Ubiquitina TiolesterasaRESUMEN
C-reactive protein is a member of the pentraxin family of oligomeric serum proteins which has been conserved through evolution, homologues having been found in every species in which they have been sought. Human C-reactive protein (hCRP) is the classical acute-phase reactant produced in large amounts in response to tissue damage and inflammation and is used almost universally as a clinical indicator of infection and inflammation. The role of hCRP in host defence and the calcium-dependent ligand-binding specificity of hCRP for phosphocholine moieties have long been recognized. In order to clarify the structural rearrangements associated with calcium binding, the reported affinity of calcium-depleted hCRP for polycations and other ligands, and the role of calcium in protection against denaturation and proteolysis, the structure of calcium-depleted hCRP has been determined by X-ray crystallography. Crystals of calcium-depleted hCRP are invariably twinned and those suitable for analysis are merohedral type II twins of point group 4 single crystals. The structure has been solved by molecular replacement using the calcium-bound hCRP structure [Shrive et al. (1996), Nature Struct. Biol. 3, 346-354]. It reveals two independent pentamers which form a face-to-face decamer across a dyad near-parallel to the twinning twofold axis. Cycles of intensity deconvolution, density modification (tenfold NCS) and model building, eventually including refinement, give a final R factor of 0.19 (R(free) = 0.20). Despite poor definition in some areas arising from the limited resolution of the data and from the twinning and disorder, the structure reveals the probable mode of twinning and the conformational changes, localized in one of the calcium-binding loops, which accompany calcium binding.