Chaperone Mimetic Strategy for Achieving Organic Room-Temperature Phosphorescence based on Confined Supramolecular Assembly.

The development of organic materials that deliver room-temperature phosphorescence (RTP) is highly interesting for potential applications such as anticounterfeiting, optoelectronic devices, and bioimaging. Herein, a molecular chaperone strategy for controlling isolated chromophores to achieve high-performance RTP is demonstrated. Systematic experiments coupled with theoretical evidence reveal that the host plays a similar role as a molecular chaperone that anchors the chromophores for limited nonradiative decay and directs the proper conformation of guests for enhanced intersystem crossing through noncovalent interactions. For deduction of structure-property relationships, various structure-related descriptors that correlate with the RTP performance are identified, thus offering the possibility to quantitatively design and predict the phosphorescent behaviors of these systems. Furthermore, application in thermal printing is well realized for these RTP materials. The present work discloses an effective strategy for efficient construction of organic RTP materials, delivering a modular model which is expected to help expand the diversity of desirable RTP systems.

Mechanism of a rabbit monoclonal antibody broadly neutralizing SARS-CoV-2 variants.

Due to the continuous evolution of SARS-CoV-2, the Omicron variant has emerged and exhibits severe immune evasion. The high number of mutations at key antigenic sites on the spike protein has made a large number of existing antibodies and vaccines ineffective against this variant. Therefore, it is urgent to develop efficient broad-spectrum neutralizing therapeutic drugs. Here we characterize a rabbit monoclonal antibody (RmAb) 1H1 with broad-spectrum neutralizing potency against Omicron sublineages including BA.1, BA.1.1, BA.2, BA.2.12.1, BA.2.75, BA.3 and BA.4/5. Cryo-electron microscopy (cryo-EM) structure determination of the BA.1 spike-1H1 Fab complexes shows that 1H1 targets a highly conserved region of RBD and avoids most of the circulating Omicron mutations, explaining its broad-spectrum neutralization potency. Our findings indicate 1H1 as a promising RmAb model for designing broad-spectrum neutralizing antibodies and shed light on the development of therapeutic agents as well as effective vaccines against newly emerging variants in the future.

Mechanism of an RBM-targeted rabbit monoclonal antibody 9H1 neutralizing SARS-CoV-2.

The COVID-19 pandemic, caused by SARS-CoV-2, has led to over 750 million infections and 6.8 million deaths worldwide since late 2019. Due to the continuous evolution of SARS-CoV-2, many significant variants have emerged, creating ongoing challenges to the prevention and treatment of the pandemic. Therefore, the study of antibody responses against SARS-CoV-2 is essential for the development of vaccines and therapeutics. Here we perform single particle cryo-electron microscopy (cryo-EM) structure determination of a rabbit monoclonal antibody (RmAb) 9H1 in complex with the SARS-CoV-2 wild-type (WT) spike trimer. Our structural analysis shows that 9H1 interacts with the receptor-binding motif (RBM) region of the receptor-binding domain (RBD) on the spike protein and by directly competing with angiotensin-converting enzyme 2 (ACE2), it blocks the binding of the virus to the receptor and achieves neutralization. Our findings suggest that utilizing rabbit-derived mAbs provides valuable insights into the molecular interactions between neutralizing antibodies and spike proteins and may also facilitate the development of therapeutic antibodies and expand the antibody library.

Enhancement of Escherichia coli Ribonuclease R Cytosine-Sensitive Activity by Single Amino Acid Substitution.

Exoribonucleases are frequently used as nuclei acids detection tools for their sequences, modifications, and structures. Escherichia coli ribonuclease R (EcR) is the prototypical exoribonuclease of the RNase II/RNB family degrading RNA in the 3'-5' direction. Different from RNase II, EcR is capable of degrading structured RNA efficiently, which makes it a potential analysis tool for various RNA species. In this work, we examined the nuclease activity of EcR degrading a series of RNA substrates with various sequences. Our biochemical work reveals that EcR is significantly sensitive to cytosine compared with other bases when catalyzing RNA degradation. EcR shows higher cytosine sensitivity compared to its homolog RNase II when degrading RNAs, and the hydrolysis process of EcR is transiently halted and produces apparent intermediate product when the 1-nt upstream of C is A or U, or G. Furthermore, the substitution of glycine with proline (G273P) in EcR enhances its cytosine sensitivity. These findings expand our understanding of EcR enzymatic activities. The EcR G273P mutant bearing higher cytosine sensitivity could help enrich cytosine trails in RNAs and will have potential implications in the detection and analysis of various RNA species especially small RNAs in biological and clinical samples.

Structural Insight Into hnRNP A2/B1 Homodimerization and DNA Recognition.

Heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1) has been identified as a nuclear DNA sensor. Upon viral infection, hnRNP A2/B1 recognizes pathogen-derived DNA as a homodimer, which is a prerequisite for its translocation to the cytoplasm to activate the interferon response. However, the DNA binding mechanism inducing hnRNP A2/B1 homodimerization is unknown. Here, we show the crystal structure of the RNA recognition motif (RRM) of hnRNP A2/B1 in complex with a U-shaped ssDNA, which mediates the formation of a newly observed protein dimer. Our biochemical assays and mutagenesis studies confirm that the hnRNP A2/B1 homodimer forms in solution by binding to pre-generated ssDNA or dsDNA with a U-shaped bulge. These results depict a potential functional state of hnRNP A2/B1 in antiviral immunity and other cellular processes.

Structures of Omicron spike complexes and implications for neutralizing antibody development.

The emergence of the SARS-CoV-2 Omicron variant is dominant in many countries worldwide. The high number of spike mutations is responsible for the broad immune evasion from existing vaccines and antibody drugs. To understand this, we first present the cryo-electron microscopy structure of ACE2-bound SARS-CoV-2 Omicron spike. Comparison to previous spike antibody structures explains how Omicron escapes these therapeutics. Secondly, we report structures of Omicron, Delta, and wild-type spikes bound to a patient-derived Fab antibody fragment (510A5), which provides direct evidence where antibody binding is greatly attenuated by the Omicron mutations, freeing spike to bind ACE2. Together with biochemical binding and 510A5 neutralization assays, our work establishes principles of binding required for neutralization and clearly illustrates how the mutations lead to antibody evasion yet retain strong ACE2 interactions. Structural information on spike with both bound and unbound antibodies collectively elucidates potential strategies for generation of therapeutic antibodies.

SHP2 allosteric inhibitor TK-453 alleviates psoriasis-like skin inflammation in mice via inhibition of IL-23/Th17 axis.

SHP2 is the first oncogenic tyrosine phosphatase encoded by PTPN11, which plays a significant regulatory role in cancer and inflammation-related diseases. Although SHP2 allosteric inhibitors have been used in phase I/II clinical trials for solid tumors, whether SHP2 inhibition alleviates psoriasis remains unclear. Here we expressed and purified SHP2 related proteins, and established an enzyme activity screening system for different conformations of SHP2. We launched an iterative medicinal chemistry program and identified the lead compound, TK-453. Importantly, TK-453 possessed stronger affinity with SHP2 than SHP099, evidenced by the cocrystal structure of SHP2/TK-453, revealing that the additional aryl-S-aryl bridge in TK-453 induces a 1.8 Å shift of the dichlorophenyl ring and an approximate 20° deviation of the pyrazine ring plane relative to SHP099. Furthermore, TK-453 significantly ameliorated imiquimod-triggered skin inflammation in mice via inhibition of the IL-23/Th17 axis, proving that SHP2 is a potential therapeutic target for psoriasis.

Robust control of floral meristem determinacy by position-specific multifunctions of KNUCKLES.

Floral organs are properly developed on the basis of timed floral meristem (FM) termination in Arabidopsis In this process, two known regulatory pathways are involved. The WUSCHEL (WUS)-CLAVATA3 (CLV3) feedback loop is vital for the spatial establishment and maintenance of the FM, while AGAMOUS (AG)-WUS transcriptional cascades temporally repress FM. At stage 6 of flower development, a C2H2-type zinc finger repressor that is a target of AG, KNUCKLES (KNU), directly represses the stem cell identity gene WUS in the organizing center for FM termination. However, how the robust FM activity is fully quenched within a limited time frame to secure carpel development is not fully understood. Here, we demonstrate that KNU directly binds to the CLV1 locus and the cis-regulatory element on CLV3 promoter and represses their expression during FM determinacy control. Furthermore, KNU physically interacts with WUS, and this interaction inhibits WUS from sustaining CLV3 in the central zone. The KNU-WUS interaction also interrupts the formation of WUS homodimers and WUS-HAIRYMERISTEM 1 heterodimers, both of which are required for FM maintenance. Overall, our findings describe a regulatory framework in which KNU plays a position-specific multifunctional role for the tightly controlled FM determinacy.

Molecular mechanism of RNase R substrate sensitivity for RNA ribose methylation.

RNA 2'-O-methylation is widely distributed and plays important roles in various cellular processes. Mycoplasma genitalium RNase R (MgR), a prokaryotic member of the RNase II/RNB family, is a 3'-5' exoribonuclease and is particularly sensitive to RNA 2'-O-methylation. However, how RNase R interacts with various RNA species and exhibits remarkable sensitivity to substrate 2'-O-methyl modifications remains elusive. Here we report high-resolution crystal structures of MgR in apo form and in complex with various RNA substrates. The structural data together with extensive biochemical analysis quantitively illustrate MgR's ribonuclease activity and significant sensitivity to RNA 2'-O-methylation. Comparison to its related homologs reveals an exquisite mechanism for the recognition and degradation of RNA substrates. Through structural and mutagenesis studies, we identified proline 277 to be responsible for the significant sensitivity of MgR to RNA 2'-O-methylation within the RNase II/RNB family. We also generated several MgR variants with modulated activities. Our work provides a mechanistic understanding of MgR activity that can be harnessed as a powerful RNA analytical tool that will open up a new venue for RNA 2'-O-methylations research in biological and clinical samples.

Molecular Mechanism of SARS-CoVs Orf6 Targeting the Rae1-Nup98 Complex to Compete With mRNA Nuclear Export.

The accessory protein Orf6 is uniquely expressed in sarbecoviruses including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which is an ongoing pandemic. SARS-CoV-2 Orf6 antagonizes host interferon signaling by inhibition of mRNA nuclear export through its interactions with the ribonucleic acid export 1 (Rae1)-nucleoporin 98 (Nup98) complex. Here, we confirmed the direct tight binding of Orf6 to the Rae1-Nup98 complex, which competitively inhibits RNA binding. We determined the crystal structures of both SARS-CoV-2 and SARS-CoV-1 Orf6 C-termini in complex with the Rae1-Nup98 heterodimer. In each structure, SARS-CoV Orf6 occupies the same potential mRNA-binding groove of the Rae1-Nup98 complex, comparable to the previously reported structures of other viral proteins complexed with Rae1-Nup98, indicating that the Rae1-Nup98 complex is a common target for different viruses to impair the nuclear export pathway. Structural analysis and biochemical studies highlight the critical role of the highly conserved methionine (M58) of SARS-CoVs Orf6. Altogether our data unravel a mechanistic understanding of SARS-CoVs Orf6 targeting the mRNA-binding site of the Rae1-Nup98 complex to compete with the nuclear export of host mRNA, which further emphasizes that Orf6 is a critical virulence factor of SARS-CoVs.

Design of wogonin-inspired selective cyclin-dependent kinase 9 (CDK9) inhibitors with potent in vitro and in vivo antitumor activity.

Wogonin, a natural product isolated from the plant Scutellaria baicalensis, has been shown to be a potent and selective inhibitor of CDK9. With the purpose of investigating the activity and selectivity of this chemical scaffold, several series of wogonin derivatives were prepared and screened for CDK9 inhibition and cellular antiproliferative activity. Among these compounds, the drug-like compound 51 showed potent activity against CDK9 (IC50 = 19.9 nM) and MV4-11 cell growth (IC50 = 20 nM). In addition, compound 51 showed much improved physicochemical properties, such as water solubility, compared with the parent compound wogonin. The follow-up studies showed that the compound 51 is selective toward CDK9-overexpressing cancer cells over normal cells. Preliminary mechanism studies on the anticancer effect indicated that 51 inhibited the proliferation of MV4-11 cells via caspase-dependent apoptosis. In addition, highlighted compound 51 showed significant antitumor activity in mouse acute myeloid leukemia (AML) models without producing apparent toxic effects in vivo, which gave us a new tool for further investigation of CDK9-targeted inhibitor as a potential antitumor drug especially for AML.

Full-Color Tunable Fluorescent and Chemiluminescent Supramolecular Nanoparticles for Anti-counterfeiting Inks.

A drive for anti-counterfeiting technology has attracted considerable interests in developing nanomaterials with a wide range of colors and tunable optical properties in solid state. Herein, with a series of conjugated polymers and based on the host-guest driven self-assembly strategy, a color-tunable supramolecular nanoparticle-based system is reported, in which full-color as well as white fluorescence can be achieved. Moreover, this fluorescent platform exhibits reversible photoswitching between quenching and emission by noncovalently introducing a photoresponsive energy acceptor. In addition, an efficient chemiluminescence system with high intensity can also be obtained in a similar manner by introducing a H2O2-responsive energy donor. Significantly, chemiluminescence is advantageous over fluorescence since there is no need for external light irradiation. More importantly, these acceptor/donor-loaded supramolecular nanoparticles exhibit fluorescence/chemiluminescence modulation ability in both solution and solid state. Therefore, this supramolecular system can be employed as fluorescent security inks for anti-counterfeiting strategies and provide a proof-of-principle application.

Multivalent methionine-functionalized biocompatible block copolymers for targeted small interfering RNA delivery and subsequent reversal effect on adriamycin resistance in human breast cancer cell line MCF-7/ADR.

BACKGROUND: Cationic polymers are outstanding representatives of the most efficient small interfering RNA (siRNA) vectors. Low cytotoxicity and siRNA protecting effect can be obtained with these cationic polymers via a variety of structural modifications. Nevertheless, the gap between their efficiency and the requirement for therapeutic processes is still noticeable. METHODS: A cationic polymer vector was synthesized via the copolymerization of N-(1,3-dihydroxy propan-2-yl)methacrylamide (DHPMA) and N-(3-aminopropyl)methacrylamide (APMA). RESULTS: APMA provides amine functionality that allows the conjugation of guanidine and methionine groups. Attributed to the hydroxy groups of DHPMA, the synthesized guanidine and methionine grafted DHPMA-b-APMA block copolymer (mDG) is water soluble and has good biocompatibility. The obtained mDG has high zeta potential, narrow molecular weight distribution, better membrane-penetrating ability, high transfection efficiency, tumor cell targeting ability and high stability. CONCLUSIONS: The synthesized polymer vector can deliver siRNA molecules into tumor cells and then reverse drug resistance by down regulation of P-glycoprotein mRNA expression.

Synthesis, evaluation and quantitative structure-activity relationship (QSAR) analysis of Wogonin derivatives as cytotoxic agents.

A novel series of 49 wogonin derivatives were synthesized by introducing group at 7-, 8- or B ring of wogonin. The cytotoxic activities against HepG2, A549 and BCG-823 cancer cell lines were also investigated in vitro. Several of them showed obvious cytotoxic activities and compound 3h possessed the highest potency against HepG2, A549, and BCG-823 with IC50 values of 1.07µM, 1.74µM and 0.98µM, respectively. A quantitative structure-activity relationship (QSAR) study of these synthetic derivatives as well as wogonin indicated that high solubility and low octanol/water partition coefficient are favorable, and excessive electrostatic properties and refractivity are unfavorable for the cytotoxic activities of these wogonin derivatives. These findings and results provide a base for further investigations.

Recent progress of cyclin-dependent kinase inhibitors as potential anticancer agents.

Deregulation of the cell cycle is a common feature in human cancer. The inhibition of cyclin-dependent kinases (CDKs), which play a crucial role in control of the cell cycle, has always been one of the most promising areas in cancer chemotherapy. This review first summarizes the biology of CDKs and then focuses on the recent advances in both broad-range and selective CDK inhibitors during the last 5 years. The design rationale, structural optimization and structure-activity relationships analysis of these small molecules have been discussed in detail and the key interactions with the amino-acid residues of the most important compounds are highlighted. Future perspectives for CDKs inhibitors will be defined in the development of highly selective CDK inhibitors, an accurate knowledge of gene control mechanism and further predictive biomarker research.

Progress in the mechanism and drug development of castration-resistant prostate cancer.

Although prostate cancer can initially respond to androgen deprivation therapy, it will inevitably relapse and switch to a castration-resistant state. The progress in understanding the mechanism of castration-resistant prostate cancer (CRPC) has led to the evolution of novel agents, including sipuleucel-T as an immunomodulant agent, enzalutamide as an androgen receptor antagonist, docetaxel as a chemotherapeutic agent and radium-223 as a radiopharmaceutical agent. In this review, we discuss the main mechanisms of CRPC and the development of promising agents along with the novel therapies in the clinic. New therapeutic challenges remain, such as the identification of predictive biomarkers and the optimal combinations of agents. Future investigation is still needed for a better understanding of CRPC.

[Efficacy evaluation of intersphincteric resection during anus-preserving operation for ultralow rectal carcinoma].

OBJECTIVE: To evaluate anorectal dynamics, function and efficacy of ultralow rectal carcinoma patients undergone intersphincteric resection(ISR). METHODS: From January 2004 to August 2007, 30 patients with ultralow rectal carcinoma(2.5-4.0 cm distance from anal edge) underwent ISR. All the patients received anorectal manometry before and after operation. The postoperative anal function was evaluated by Williams continence standard and the treatment outcome was followed up. RESULTS: After ISR operation, anal resting pressure, maximum squeeze pressure and maximum tolerance volume of the rectum decreased significantly (all P<0.01) and restored gradually, but not to normal. The rectal anal inhibitory reflex disappeared in 27 patients(90.0%) and was not improved. According to Williams continence standard, 86.7%, 93.3% and 96.7% of patients obtained acceptable anal function in 3, 6, and 12 months after operation respectively. During follow-up of 12 to 44 months, all the patients were still alive and no patient developed pelvis or local recurrence, distant metastasis and anastomotic leakage. Fecal eczema of anus occurred in 10 patients, colonic mucosa prolapse in 2 patients and stenosis of anal canal in one patient. CONCLUSION: ISR for ultralow rectal carcinoma can not only attain radical treatment outcome, but also preserve anal sphincter.

[Combined preoperative xeloda and radiotherapy for lower rectal cancer].

OBJECTIVE: To evaluate the effect of combined preoperative xeloda and pelvic radiotherapy on locally advanced lower rectal cancer. METHODS: Sixty lower rectal cancer patients were divided randomly into two groups. 30 patients (Group A) were treated with operation alone and 30 patients (Group B) were treated with xeloda and radiotherapy before operation. RESULTS: The operative resection, anal preservation and local recurrence rates were 86.66%, 33.33%, 15.38% in group A and 100%, 83.33%, 0% in group B (P < 0.05 and P < 0.01). CONCLUSION: Combined preoperative xeloda and radiotherapy for lower rectal cancer is able to significantly improve the operative resection, anal preservation and decrease the local recurrence rates.