The interaction of the eukaryotic translation initiation factor eIF4E with the initiation factor eIF4G recruits the 40S ribosomal particle to the 5′ end of mRNAs, facilitates scanning to the AUG start codon, and is crucial for eukaryotic translation of nearly all genes. Efficient recruitment of the 40S particle is particularly important for translation of mRNAs encoding oncoproteins and growth-promoting factors, which often harbor complex 5′ UTRs and require efficient initiation. Thus, inhibiting the eIF4E/eIF4G interaction has emerged as a previously unpursued route for developing anticancer agents. Indeed, we discovered small-molecule inhibitors of this eIF4E/eIF4G interaction (4EGIs) that inhibit translation initiation both in vitro and in vivo and were used successfully in numerous cancer-biology and neurobiology studies. However, their detailed molecular mechanism of action has remained elusive. Here, we show that the eIF4E/eIF4G inhibitor 4EGI-1 acts allosterically by binding to a site on eIF4E distant from the eIF4G binding epitope. Data from NMR mapping and high-resolution crystal structures are congruent with this mechanism, where 4EGI-1 attaches to a hydrophobic pocket of eIF4E between β-sheet 2 (L 60 -T 68 ) and α-helix 1 (E 69 -N 77 ), causing localized conformational changes mainly in the H 78 -L 85 region. It acts by unfolding a short 3 10 -helix (S 82 -L 85 ) while extending α-helix 1 by one turn (H 78 -S 82 ). This unusual helix rearrangement has not been seen in any previous eIF4E structure and reveals elements of an allosteric inhibition mechanism leading to the dislocation of eIF4G from eIF4E. allosteric inhibitor | NMR spectroscopy | inhibitor of protein-protein interaction T he translation initiation factor eIF4E is overexpressed in numerous human cancers and drives cellular transformation, tumorigenesis, and metastatic progression in preclinical and clinical experiments. These oncogenic processes are driven selectively, increasing the translation of a subset of oncogenic mRNAs that has highly structured 5′ UTRs (1, 2) or other regulatory elements (3). eIF4E also seems to play critical roles in learning and memory (4, 5). The protein-protein interaction between eIF4E and eIF4G is a decisive event in eukaryotic protein synthesis, because the interaction of eIF4E with eIF4G is critical for the formation of the trimeric eIF4F complex consisting of eIF4E, the multidomain scaffold protein eIF4G, and RNA helicase eIF4A. This eIF4F complex along with eIF3 mediate the recruitment of the 40S ribosomal particle to the 5′ cap of mRNA. Thus, targeting the eIF4E/eIF4G interaction has emerged as an opportunity for the development of previously unavailable anticancer agents (6). Indeed, small-molecule inhibitors of this interaction (4EGIs, which bind to eIF4E and prevent eIF4G recruitment) were discovered that exhibit this desired activity in vitro and in vivo (7). These agents have now been widely used in numerous cancer-biology (8-15) and neurobiology studies (16-18).

Reduction of anticancer prodrugs such as ctc-[PtCl(2)(CH(3)CO(2))(2)(NH(3))(Am)] can yield three products in addition to the expected cis-[PtCl(2)(NH(3))(Am)]. A possible explanation is that reduction proceeds by several pathways where in addition to the loss of two axial ligands, one axial (acetato) and one equatorial (chlorido) ligand, or two equatorial ligands are eliminated.

Novel antibacterials with activity against the Gram-negative bacteria associated with nosocomial infections, including Escherichia coli and other Enterobacteriaceae, are urgently needed due to the increasing prevalence of multidrug-resistant strains. A major obstacle that has stalled progress on nearly all small-molecule classes with potential for activity against these species has been achieving sufficient whole-cell activity, a difficult challenge due to the formidable outer membrane and efflux barriers intrinsic to these species. Using a set of compound design principles derived from available information relating physicochemical properties to Gram-negative entry or activity, we synthesized and evaluated a focused library of oxazolidinone analogues, a currently narrow spectrum class of antibacterials active only against Gram-positive bacteria. In this series, we have explored the effectiveness for improving Gram-negative activity by identifying and combining beneficial structural modifications in the C-ring region. We have found polar and/or charge-carrying modifications that, when combined in hybrid C-ring analogues, appear to largely overcome the efflux and/or permeability barriers, resulting in improved Gram-negative activity. In particular, those analogues least effected by efflux and the permeation barrier had significant zwitterionic character.

Heme-regulated inhibitor kinase (HRI), an eukaryotic translation initiation factor 2 alpha (eIF2α) kinase, plays critical roles in cell proliferation, differentiation, and adaptation to cytoplasmic stress. HRI is also a critical modifier of hemoglobin disorders such as β-thalassemia. We previously identified N,N′-diarylureas as potent activators of HRI suitable for studying biology of this important kinase. To expand the repertoire of chemotypes that activate HRI we screened a ~1,900 member N,N′-disubstituted urea library in the surrogate eIF2α phosphorylation assay identifying N-aryl,N′-cyclohexylphenoxyurea as a promising scaffold. We validated hit compounds as a bona-fide HRI activators in secondary assays and explored contributions of substitutions on the N-aryl and N′-cyclohexylphenoxy groups to their activity by studying focused libraries of complementing analogs. We tested these N-aryl,N′-cyclohexylphenoxyureas in the surrogate eIF2α phosphorylation and cell proliferation assays, demonstrating significantly improved bioactivities and specificities. We consider these compounds to represent lead candidates for the development of potent and specific HRI activators.