Antimitotics that target tubulin are among the most useful chemotherapeutic drugs, but their clinical activity is often limited by the development of multidrug resistance. We recently discovered the novel small-molecule DJ101 as a potent and metabolically stable tubulin inhibitor that can circumvent the drug efflux pumps responsible for multidrug resistance of existing tubulin inhibitors. In this study, we determined the mechanism of action of this drug. The basis for its activity was illuminated by solving the crystal structure of DJ101 in complex with tubulin at a resolution of 2.8Å. Investigations of the potency of DJ101 in a panel of human metastatic melanoma cell lines harboring major clinically relevant mutations defined IC values of 7-10 nmol/L. In cells, DJ101 disrupted microtubule networks, suppressed anchorage-dependent melanoma colony formation, and impaired cancer cell migration. In melanoma-bearing mice, DJ101 administration inhibited tumor growth and reduced lung metastasis in the absence of observable toxicity. DJ101 also completely inhibited tumor growth in a paclitaxel-resistant xenograft mouse model of human prostate cancer (PC-3/TxR), where paclitaxel was minimally effective. Our findings offer preclinical proof of concept for the continued development of DJ101 as a next-generation tubulin inhibitor for cancer therapy. These findings offer preclinical proof of concept for the continued development of DJ101 as a next-generation antitubulin drug for cancer therapy. .

Human dihydroorotate dehydrogenase (hDHODH) is an attractive target for cancer therapy. Based on its crystal structure, we designed and synthesized a focused compound library containing the structural moiety of 1,4-benzoquinone, which possesses reactive oxygen species (ROS) induction capacity. Compound 3s with a naphtho­[2,3-d]­[1,2,3]­triazole-4,9-dione scaffold exhibited inhibitory activity against hDHODH. Further optimization led to compounds 11k and 11l, which inhibited hDHODH activity with IC50 values of 9 and 4.5 nM, respectively. Protein–ligand cocrystal structures clearly depicted hydrogen bond and hydrophobic interactions of 11k and 11l with hDHODH. Compounds 11k and 11l significantly inhibited leukemia cell and solid tumor cell proliferation and induced ROS production, mitochondrial dysfunction, apoptosis, and cell cycle arrest. Nanocrystallization of compound 11l displayed significant in vivo antitumor effects in the Raji xenograft model. Overall, this study provides a novel bifunctional compound 11l with hDHODH inhibition and ROS induction efficacy, which represents a promising anticancer lead worthy of further exploration.

Developmental endothelial cell locus-1 (Del-1) glycoprotein is secreted by endothelial cells and a subset of macrophages. Del-1 plays a regulatory role in vascular remodeling and functions in innate immunity through interaction with integrin α(V)β(3). Del-1 contains 3 epidermal growth factor (EGF)-like repeats and 2 discoidin-like domains. An Arg-Gly-Asp (RGD) motif in the second EGF domain (EGF2) mediates adhesion by endothelial cells and phagocytes. We report the crystal structure of its 3 EGF domains. The RGD motif of EGF2 forms a type II' β turn at the tip of a long protruding loop, dubbed the RGD finger. Whereas EGF2 and EGF3 constitute a rigid rod via an interdomain calcium ion binding site, the long linker between EGF1 and EGF2 lends considerable flexibility to EGF1. Two unique O-linked glycans and 1 N-linked glycan locate to the opposite side of EGF2 from the RGD motif. These structural features favor integrin binding of the RGD finger. Mutagenesis data confirm the importance of having the RGD motif at the tip of the RGD finger. A database search for EGF domain sequences shows that this RGD finger is likely an evolutionary insertion and unique to the EGF domain of Del-1 and its homologue milk fat globule-EGF 8.

SummaryDeleted in colorectal cancer (DCC) is a receptor for the axon guidance cues netrin-1 and draxin. The interactions between these guidance cues and DCC play a key role in the development of the nervous system. In the present study, we reveal the crystal structure of the Nterminal four Ig-like domains of DCC. The molecule folds into a horseshoe-like configuration. We demonstrate that this horseshoe conformation of DCC is required for guidance-cue-mediated axonal attraction. Structure-based mutations that disrupt the DCC horseshoe indeed impair its function. A comparison of the DCC horseshoe with previously described horseshoe structures has revealed striking conserved structural features and important sequence signatures. Using these signatures, a genome-wide search allows us to predict the N-terminal horseshoe arrangement in a number of other cell surface receptors, nearly all of which function in the nervous system. The N-terminal horseshoe appears to be evolutionally selected as a platform for neural receptors.

The αβ T cell receptor (TCR) is a multimeric complex whose β chain plays a crucial role in thymocyte development as well as antigen recognition by mature T lymphocytes. We report here crystal structures of individual β subunits, termed N15β (Vβ5.2Dβ2Jβ2.6Cβ2) and N30β (Vβ13Dβ1Jβ1.1Cβ2), derived from two αβ TCRs specific for the immunodominant vesicular stomatitis virus octapeptide (VSV-8) bound to the murine H-2Kb MHC class I molecule. The crystal packing of the N15β structure reveals a homodimer formed through two Vβ domains. The Vβ/Vβ module is topologically very similar to the Vα/Vβ module in the N15αβ heterodimer. By contrast, in the N30β structure, the Vβ domain’s external hydrophobic CFG face is covered by the neighboring molecule’s Cβ domain. In conjunction with systematic investigation of previously published TCR single-subunit structures, we identified several conserved residues forming a concave hydrophobic patch at the center of the CFG outer face of the Vβ and other V-type Ig-like domains. This hydrophobic patch is shielded from solvent exposure in the crystal packing, implying that it is unlikely to be thermodynamically stable if exposed on the thymocyte surface. Accordingly, we propose a dimeric pre-TCR model distinct from those suggested previously by others and discuss its functional and structural implications.

Comparison of Dscam1 structures reveals the detailed mechanism of Dscam1 isoform-specific recognition.

Large scale genomic aberrations including duplication, deletion, translocation, and other structural changes are the cause of a subtype of hereditary genetic disorders and contribute to onset or progress of cancer. The current prime editor, PE2, consisting of Cas9-nickase and reverse transcriptase enables efficient editing of genomic deletion and insertion, however, at small scale. Here, we designed a novel prime editor by fusing reverse transcriptase (RT) to nuclease wild-type Cas9 (WT-PE) to edit large genomic fragment. WT-PE system simultaneously introduced a double strand break (DSB) and a single 3′ extended flap in the target site. Coupled with paired prime editing guide RNAs (pegRNAs) that have complementary sequences in their 3′ terminus while target different genomic regions, WT-PE produced bi-directional prime editing, which enabled efficient and versatile large-scale genome editing, including large fragment deletion up to 16.8 megabase (Mb) pairs and chromosomal translocation. Therefore, our WT-PE system has great potential to model or treat diseases related to large-fragment aberrations.

We present a base editing system, in which base editors are attached to different sites of sgRNA scaffold (sgBE). Each independent sgBE has its own specific editing pattern for a given target site. Among tested sgBEs, sgBE-SL4, in which deaminase is attached to the last stem-loop of sgRNA, yields the highest editing efficiency in the window several nucleotides next to the one edited by BE3. sgBE enables the simultaneous editing of adenine and cytosine. Finally, in order to facilitate in vivo base editing, we extend our sgBE system to an AAV-compatible Cas9, SaCas9 (Staphylococcus aureus), and observe robust base editing.