Mammalian Exo1 encodes both structural and catalytic functions that play distinct roles in essential biological processes

Mammalian Exonuclease 1 (EXO1) is an evolutionarily conserved, multifunctional exonuclease involved in DNA damage repair, replication, immunoglobulin diversity, meiosis, and telomere maintenance. It has been assumed that EXO1 participates in these processes primarily through its exonuclease activity, but recent studies also suggest that EXO1 has a structural function in the assembly of higher-order protein complexes. To dissect the enzymatic and nonenzymatic roles of EXO1 in the different biological processes in vivo, we generated an EXO1-E109K knockin (Exo1(EK)) mouse expressing a stable exonuclease-deficient protein and, for comparison, a fully EXO1-deficient (Exo1(null)) mouse. In contrast to Exo1(null/null) mice, Exo1(EK/EK) mice retained mismatch repair activity and displayed normal class switch recombination and meiosis. However, both Exo1-mutant lines showed defects in DNA damage response including DNA double-strand break repair (DSBR) through DNA end resection, chromosomal stability, and tumor suppression, indicating that the enzymatic function is required for those processes. On a transformation-related protein 53 (Trp53)-null background, the DSBR defect caused by the E109K mutation altered the tumor spectrum but did not affect the overall survival as compared with p53-Exo1(null) mice, whose defects in both DSBR and mismatch repair also compromised survival. The separation of these functions demonstrates the differential requirement for the structural function and nuclease activity of mammalian EXO1 in distinct DNA repair processes and tumorigenesis in vivo

In vivo dual-modality MR and near-infrared fluorescence imaging of gastric cancer neovasculature with targeted multi-functionalized nanoparticles

Objective: To explore the feasibility of dual-modality probe to in vivo target angiogenesis of gastric cancer on MRI and near-infrared fluorescence (NIRF) optical imaging. Methods: Cy5.5-GX1 with magnetic FeO nanoparticles were conjugated, resulting in dual-modality probe DPs. The hydrodynamic size and Zeta potential of DPs were analyzed by nano-ZS. Twelve male nude mice were obtained and established gastric adenocarcinoma subcutaneous transplantation tumor model. Twelve nude mice were divided into experimental group and control group (n=6 for each) by using completely random experimental design, then intravenously injected the same volume of DPs and FeO-Cy5.5. MRI was applied before and 4, 8, 12, 18, 24 hours respectively after injections of nanoparticles to follow the changes of signals. For the evaluation of the MR images, the contrast to noise ratio (CNR) were calculated, and the different groups were compared with analysis of variance. MR images of the same level were selected before and 12 h after injections of nanoparticles in two groups and the percentage of reduced pixels was calculated, which were compared with the paired t test. At the same time, the time-resolved accumulation of the nanoparticles in the tumors were observed by using in vivo fluorescence imaging at 0, 4, 8, 12, 18, 24 hours after injecting nanoparticles, respectively. Then tumor and normal tissues were collected, and ex vivo optical imaging and histopathology were performed on the tissues. Results: At room temperature, the hydrodynamic size of FeO-Cy5.5 was(38.23 ± 0.06)nm and the Zeta potential was (0.29 ± 0.16)mV, and the hydrodynamic size of DPs was (39.49 ± 0.16) nm and the Zeta potential was (- 4.15 ± 0.79) mV. The coupled rate of DPs with polypeptide was >90%. The MRI signals of reticuloendothelial system were reduced significantly in experiment and control group. The tumor CNR of experiment group before and 4, 8, 12, 18, 24 h after injection were 18.27 ± 2.19, 18.40 ± 2.00, 10.22 ± 1.97, 9.25 ± 0.44, 20.28 ± 1.46 and 22.41 ± 1.71 (F= 49.55, P0.05). The percentage of MR signals decrease of the tumor periphery and central area were(33.0 ± 2.7)% and (22.0 ± 1.6)%, respectively in experiment group and that of control group were (8.3 ± 1.2)% and (3.8 ± 0.9)% respectively (t values were - 7.872 and 6.678, P< 0.01). The tumor fluorescence intensity of experimental group showed the high contrast to background tissue during 2 to 48 h p.i, but there was no significant difference in control group. Furthermore, ex vivo evaluation of excised organs showed DPs was predominantly taken up by the lumor and lung at 48 h p.i. Tumor neovascularization was mainly distributed in the tumor periphery area. Iron-positive cells were detected in the tumor of experiment group. The normal kidney tissues of the two groups and the tumor of control group were consistently negative for iron staining. Conclusion: DPs can selectively be delivered into gastric cancer and this novel receptor-targeted nanoparlicle could be used for MRI and NIRF optical imaging

Preparation and characterization of dual-modality molecular probes for imaging angiogenesis of gastric cancer

Objective: To develop an MR optical dual-modality probe targeting angiogenesis of gastric; cancer and to study its physical characteristics, in vitro cytotoxicity and magnetic effects of different pulse sequences on 3 T clinical MR scanner. Methods: We conjugated GXl-Cy5.5, a novel gastric cancer neo-vasculature targeted peptide labeled with Cy5.5, to the surface functionalized magnetic: nanoparticles according to different molecular weights (1:100, 1:500), resulting in dual-modality probe DPs, and DPs (named DPs). The hydrodynamic size and zeta potential of DPs and DPs were analyzed by nano-ZS. The human umbilical vein endothelial cells (HUVECs) and BGC-823 cells were treated with DPs for 24 h, and methyl thiazol tetrazolium (MTT) method was used to detect the survival rate of cells. DPs with different concentrations were scanned on different MR sequences, and then the relative signal intensity was observed. The absorbance of HUVECs and BGC823 cells treated with DPs of different concentration (0.00, 1.25, 2.50, 15.00, 50.00, 100.00 and 150.00 (xg/ml) were compared with single factor analysis of variance. Relative signal intensity of different MR sequences was compared using a paired Wilcoxon signed-rank test. Results: The dual-modality probe targeting angiogenesis of gastric cancer was successfully constructed. The hydrodynamic size of iron oxide nanoparticles, DPs and DPswas (35.23±0.07), (39.49±0.16) and (40.43±1.70) nm and the Zeta potential was (0.31±0.20), (-4.15±0.79) and (-10.51±2.37) mV. The coupled rates of DPs and DPs with polypeptide were 92% and 94% respectively. The absorbance of HUVECs and BGC823 cells treated with DPs of different concentrations were 0.76±0.04, 0.80±0.03, 0.79±0.05, 0.75±0.06, 0.74±0.05, 0.77±0.01, 0.71±0.04 and 0.38±0.04, 0.43±0.04, 0.41±0.03, 0.43±0.07, 0.44±0.04, 0.41±0.07 and 0.40±0.04, there was no statistical significance (F=0.94, 0.51; P≤0.05). The signal intensity increased first and then decreased following the increasing concentrations of DPs on TWI, especially on FSPGR TWI (Z=-3.294, P10 μg/ml, the signal intensity on SSFSE TWI was significantly decreased compared to FSE TWI (Z=-2.023,

Direction controllable inverse transition radiation from the spatial dispersion in a graphene-dielectric stack

Transition radiation (TR) induced by electron-matter interaction usually demands vast accelerating voltages, and the radiation angle cannot be controlled. Here we present a mechanism of direction controllable inverse transition radiation (DCITR) in a graphene-dielectric stack excited by low-velocity electrons. The revealed mechanism shows that the induced hyperbolic-like spatial dispersion and the superposition of the individual bulk graphene plasmons (GPs) modes make the fields, which are supposed to be confined on the surface, radiate in the stack along a special radiation angle normal to the Poynting vector. By adjusting the chemical potential of the graphene sheets, the radiation angle can be controlled. And owing to the excitation of bulk GPs, only hundreds of volts for the accelerating voltage are required and the field intensity is dramatically enhanced compared with that of the normal TR. Furthermore, the presented mechanism can also be applied to the hyperbolic stack based on semiconductors in the infrared region as well as noble metals in the visible and ultraviolet region. Accordingly, the presented mechanism of DCITR is of great significance in particle detection, radiation emission, and so on

Theoretical analysis and spatial–temporal dynamic simulation of radiation from graphene

In this paper, the terahertz (THz) radiation based on the graphene is studied by theoretical analysis and particle-in-cell (PIC) simulation. We present the transition radiation (TR) of the charged particle traversing a monoatomic graphene layer under arbitrary incidence. By theoretical analysis, we find strongly tunable effects of the radiation field distribution related to the electron’s incident angle, substrate permittivity and graphene conductivity. In the case of the normal incidence, the transition radiation exhibits strong symmetry and considerably more intensive than that at oblique incidence. Furthermore, the plasmon and radiation are simulated by a PIC code with the method of equivalent permittivity to deal graphene. With the PIC code, we observe the spatial–temporal dynamics of plasmon and transition radiation from graphene. Meanwhile, the PIC simulation results of radiation are in good agreement with those by theoretical analysis

Gold nanoparticle-directed autophagy intervention for antitumor immunotherapy via inhibiting tumor-associated macrophage M2 polarization

Tumor-associated macrophages (TAMs), one of the dominating constituents of tumor microenvironment, are important contributors to cancer progression and treatment resistance. Therefore, regulation of TAMs polarization from M2 phenotype towards M1 phenotype has emerged as a new strategy for tumor immunotherapy. Herein, we successfully initiated antitumor immunotherapy by inhibiting TAMs M2 polarization via autophagy intervention with polyethylene glycol-conjugated gold nanoparticles (PEG-AuNPs). PEG-AuNPs suppressed TAMs M2 polarization in both in vitro and in vivo models, elicited antitumor immunotherapy and inhibited subcutaneous tumor growth in mice. As demonstrated by the mRFP-GFP-LC3 assay and analyzing the autophagy-related proteins (LC3, beclin1 and P62), PEG-AuNPs induced autophagic flux inhibition in TAMs, which is attributed to the PEG-AuNPs induced lysosome alkalization and membrane permeabilization. Besides, TAMs were prone to polarize towards M2 phenotype following autophagy activation, whereas inhibition of autophagic flux could reduce the M2 polarization of TAMs. Our results revealed a mechanism underlying PEG-AuNPs induced antitumor immunotherapy, where PEG-AuNPs reduce TAMs M2 polarization via induction of lysosome dysfunction and autophagic flux inhibition. This study elucidated the biological effects of nanomaterials on TAMs polarization and provided insight into harnessing the intrinsic immunomodulation capacity of nanomaterials for effective cancer treatment.</p

Inactivation of Exonuclease 1 in mice results in DNA mismatch repair defects, increased cancer susceptibility, and male and female sterility

Exonuclease 1 (Exo1) is a 5′–3′ exonuclease that interacts with MutS and MutL homologs and has been implicated in the excision step of DNA mismatch repair. To investigate the role of Exo1 in mammalian mismatch repair and assess its importance for tumorigenesis and meiosis, we generated an Exo1 mutant mouse line. Analysis of Exo1(−/−) cells for mismatch repair activity in vitro showed that Exo1 is required for the repair of base:base and single-base insertion/deletion mismatches in both 5′ and 3′ nick-directed repair. The repair defect in Exo1(−/−) cells also caused elevated microsatellite instability at a mononucleotide repeat marker and a significant increase in mutation rate at the Hprt locus. Exo1(−/−) animals displayed reduced survival and increased susceptibility to the development of lymphomas. In addition, Exo1(−/−) male and female mice were sterile because of a meiotic defect. Meiosis in Exo1(−/−) animals proceeded through prophase I; however, the chromosomes exhibited dynamic loss of chiasmata during metaphase I, resulting in meiotic failure and apoptosis. Our results show that mammalian Exo1 functions in mutation avoidance and is essential for male and female meiosis