A dual-mode fluorescence and colorimetric sensing platform for efficient detection of ofloxacin in aquatic products using iron alkoxide nanozyme.

Trace detection of ofloxacin (OFL) with high sensitivity, reliability, and visual clarity is challenging. To address this, a novel dual-modal aptasensor with fluorescence-colorimetric capabilities was designed that exploit the target-induced release of 3,3',5,5'-tetramethylbenzidine (TMB) molecules from aptamer-gated mesoporous silica nanoparticles (MSNs), the oxidase-like activity of iron alkoxide (IA) nanozyme, and the fluorescence attributes of core-shell upconversion nanoparticles. Therefore, the study reports a dual mode detection, with a fluorescence detection range for OFL spanning from 0.1 µg/kg to 1000 µg/kg (and a detection limit of 0.048 µg/kg). Additionally, the colorimetric method offered a linear detection range of 0.3 µg/kg to 1000 µg/kg, with a detection limit of 0.165 µg/kg. The proposed biosensor had been successfully applied to the determination of OFL content in real samples with satisfactory recoveries (78.24-96.14 %).

Circular mRNA-based TCR-T offers a safe and effective therapeutic strategy for treatment of cytomegalovirus infection.

Circular mRNA (cmRNA) is particular useful due to its high resistance to degradation by exonucleases, resulting in greater stability and protein expression compared to linear mRNA. T cell receptor (TCR)-engineered T cells (TCR-T) represent a promising means of treating viral infections and cancer. This study aimed to evaluate the feasibility and efficacy of cmRNA in antigen-specific-TCR discovery and TCR-T therapy. Using human cytomegalovirus (CMV) pp65 antigen as a model, we found that the expansion of pp65-responsive T cells was induced more effectively by monocyte-derived dendritic cells transfected with pp65-encoding cmRNA compared with linear mRNA. Subsequently, we developed cmRNA-transduced pp65-TCR-T (cm-pp65-TCR-T) that specifically targets the CMV-pp65 epitope. Our results showed that pp65-TCR could be expressed on primary T cells for more than 7 days. Moreover, both in vitro killing and in vivo CDX models demonstrated that cm-pp65-TCR-T cells specifically and persistently kill pp65-and HLA-expressing tumor cells, significantly prolonging the survival of mice. Collectively, our results demonstrated that cmRNA can be used as a more effective technical approach for antigen-specific TCR isolation and identification, and cm-pp65-TCR-T may provide a safe, non-viral, non-integrated therapeutic approach for controlling CMV infection, particularly in patients who have undergone allogeneic hematopoietic stem cell transplantation.

Colossal Anisotropic Thermal Expansion in a Diazo-Functionalized Compound with Switchable Solid-State Behavior.

Achieving substantial anisotropic thermal expansion (TE) in solid-state materials is challenging as most materials undergo volumetric expansion upon heating. Here, we describe colossal, anisotropic TE in crystals of an organic compound functionalized with two azo groups. Interestingly, the material exhibits distinct and switchable TE behaviors within different temperature regions. At high temperature, two-dimensional, area zero TE and colossal, positive linear TE (α=211 MK-1 ) are attained due to dynamic motion, while at low temperature, moderate positive TE occurs in all directions. Investigation of the solid-state motion showed the change in enthalpy and entropy are quite different in the two temperature regions and solid-state NMR experiments support motion in the solid. Cycling experiments demonstrate that the solid-state motions and TE behaviors are completely reversible. These results reveal strategies for designing significant anisotropic and switchable behaviors in solid-state materials.

Wdr5 is essential for fetal erythropoiesis and hematopoiesis.

WDR5 is a highly conserved protein that performs multiple scaffolding functions in the context of chromatin. However, efforts to understand the function of WDR5 in normal tissues physiologically are quite limited so far. In our study, we explored the function of Wdr5 in erythropoiesis and hematopoiesis by using a hematopoietic-specific Wdr5 knockout mouse model. We found that loss of Wdr5 mediated by Vav-iCre leads to embryonic lethality with defective erythropoiesis. In addition, Wdr5-deficiency completely impairs the hematopoietic stem and progenitor cells function and might alter the immunophenotype of these stem cells and progenitors by decreasing c-Kit expression. Collectively, we identified the pivotal role of Wdr5 in fetal hematopoiesis and erythropoiesis as the de novo findings.

Bipyridine-mediated fluorescence charge transfer process based on copper ion grafted upconversion nanoparticle platform for ciprofloxacin sensing in aquatic products.

In this work, an ultrasensitive ciprofloxacin (CIP) detection strategy has been established based on copper (Cu2+) ions-induced strong charge transfer in poly acrylic acid (PAA) functionalized upconversion nanoparticles (UCNPs)/2,2-bipyridine (bipy) system. The positively charged Cu2+ ions electrostatically adhere to the surface of the PAA-UCNPs and deactivate the fluorescence via a charge transfer process. The bipy in this hybrid system controls the aggregation by chelating in proximity to the Cu2+ center. Due to the strong affinity between pyridone oxygen and carboxy oxygen, CIP coordinates in high stoichiometry with the bipy-Cu complex as compared to the PAA-UCNPs, causing the trapped fluorescence to be released in an amount equivalent to the target concentration. Under the optimum assay conditions, a good calibration plot (0.05-1000 ng/mL) was acquired with a detection limit of 0.13 ng/mL. The satisfactory recoveries (85.93-96.87%) for real prawn and fish samples were further validated by enzyme-linked immunoassays (P > 0.05).

Differences in thermal expansion and motion ability for herringbone and face-to-face π-stacked solids.

A series of aromatic organic molecules functionalized with different halogen atoms (I/ Br), motion-capable groups (olefin, azo or imine) and molecular length were designed and synthesized. The molecules self-assemble in the solid state through halogen bonding and exhibit molecular packing sustained by either herringbone or face-to-face π-stacking, two common motifs in organic semiconductor molecules. Interestingly, dynamic pedal motion is only achieved in solids with herringbone packing. On average, solids with herringbone packing exhibit larger thermal expansion within the halogen-bonded sheets due to motion occurrence and molecular twisting, whereas molecules with face-to-face π-stacking do not undergo motion or twisting. Thermal expansion along the π-stacked direction is surprisingly similar, but slightly larger for the face-to-face π-stacked solids due to larger changes in π-stacking distances with temperature changes. The results speak to the importance of crystal packing and intermolecular interaction strength when designing aromatic-based solids for organic electronics applications.

Thermal Expansion Properties and Mechanochemical Synthesis of Stoichiometric Cocrystals Containing Tetrabromobenzene as a Hydrogen- and Halogen-Bond Donor.

The solution and mechanochemical synthesis of two cocrystals that differ in the stoichiometric ratio of the components (stoichiometric cocrystals) is reported. The components in the stoichiometric cocrystals interact through hydrogen or hydrogen/halogen bonds and differ in π-stacking arrangements. The difference in structure and noncovalent interactions affords dramatically different thermal expansion behaviors in the two cocrystals. At certain molar ratios, the cocrystals are obtained concomitantly; however, by varying the ratios, a single stoichiometric cocrystal is achieved using mechanochemistry.

Preventive and Therapeutic Effects of a Novel JAK Inhibitor SHR0302 in Acute Graft-Versus-Host Disease.

Acute graft-versus-host disease (aGVHD) is one of the most common complications of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Janus kinase (JAK) inhibitors are considered as reliable and promising agents for patients with aGVHD. The prophylactic and therapeutic effects of SHR0302, a novel JAK inhibitor, were evaluated in aGVHD mouse models. The overall survival (OS), progression-free survival (PFS), bodyweight of mice, GVHD scores were observed and recorded. The bone marrow and spleen samples of diseased model mice or peripheral blood of patients were analyzed. SHR0302 could prevent and reverse aGVHD in mouse models with preserving graft-versus-tumor effect. Functionally, SHR0302 improved the OS and PFS, restored bodyweight, reduced GVHD scores, and reduced immune cells infiltrated in target tissues. SHR0302 treatment also enhanced the hematopoietic reconstruction compared to the control group. Mechanistically, our results suggested that SHR0302 could inhibit the activation of T cells and modulate the differentiation of helper T (Th) cells by reducing Th1 and increasing regulatory T (Treg) cells. In addition, SHR0302 decreased the expression of chemokine receptor CXCR3 on donor T cells and the secretion of cytokines or chemokines including interleukin (IL)-6, interferon γ (IFN-γ), tumor necrosis factor α (TNF-α), CXCL10, etc. thereby destroying the IFN-γ/CXCR3/CXCL10 axis which promotes the progression of GVHD. Besides, SHR0302 decreased the phosphorylation of JAK and its downstream STATs, AKT and ERK1/2, which ultimately regulated the activation, proliferation, and differentiation of lymphocytes. Experiments on primary cells from aGVHD patients also confirmed the results. In summary, our results indicated that JAK inhibitor SHR0302 might be used as a novel agent for patients with aGVHD.

[Establishment of A Mixed Chimeric Mouse Model of Allogeneic Bone Marrow Transplantation and Its Influencing Factors].

OBJECTIVE: To establish a mouse mixed chimerism (MC) model of nonmyeloablative allogeneic bone marrow transplantation(allo-BMT) and explore its affecting factors. METHODS: The MC model was established by nonmyeloablative allo-BMT followed by high-dose post-transplant cyclophosphamide (PTCY). 123 mice in the experiments was retrospectively analyzed, and the factors related with the chimerism were explored with the univariate and multivariate logistic regression analysis. A multivariate linear regression was performed by R project to obtain a mathematical model for predicting the chimeric level with relevant affecting factors. RESULTS: The model presented mixed chimerism on day 14 after transplantation, and was characterized by a donor lymphocyte infusion (DLI) which significantly promoted donor engraftment on day 15, but transfplantation of PBS in control group was failed. Among 123 mice, 47 (38.21%) mice were MC, while 76 (61.79%) mice were non-MC in 123 mice, respectively; univariate analysis showed that the baseline body weight of mice (P=0.001, 17.84±1.19 g vs 18.50±0.94 g), total body irradiation(TBI，P=0.048) and the using of cyclophosphamide (P=0.16) were affected the chimeric state of mice, while the number of infusing cells and the time of detection showed no significant effects. Multivariate regression analysis showed that under certain conditions, the body weight of mice on day 0 was an independent factor affecting chimeric levels (OR=0.493, 95% CI 0.307-0.791, P=0.003). Through R project multiple linear regression, the math model was achieved, which was chimerism=6.09-12×weight(g)+80.03×TBI(Gy)-4.4×cell-counts (× 107) +0.38×CTX (mg/kg), R2=0.5841, P<0.001. CONCLUSION: The experiment presents a method for establishing a mixed chimeric mice model after non-myeloablative bone marrow transplantation and constructs a mathematical model with relevant factors affected chimerism status.

Controlling thermal expansion within mixed cocrystals by tuning molecular motion capability.

Controlling thermal expansion (TE) behaviors of organic materials is challenging because several mechanisms can govern TE, such as noncovalent interaction strength and structural motions. Here, we report the first demonstration of tuning TE within organic solids by using a mixed cocrystal approach. The mixed cocrystals contain three unique molecules, two of which are present in variable ratios. These two molecules either lack or exhibit the ability to undergo molecular motion in the solid state. Incorporation of higher ratios of motion-capable molecules results in larger, positive TE along the motion direction. Addition of a motion-incapable molecule affords solids that undergo less TE. Fine-tuned TE behavior was attained by systematically controlling the ratio of motion-capable and -incapable molecules in each solid.

Comparative analysis of brain pathology in heparan sulphate storing mucopolysaccharidoses.

The cause of neurodegeneration in MPS mouse models is the focus of much debate and what the underlying cause of disease pathology in MPS mice is. The timing of development of pathology and when this can be reversed or impacted is the key to developing suitable therapies in MPS. This study is the first of its kind to correlate the biochemical changes with the functional outcome as assessed using non-invasive behaviour testing across multiple mucopolysaccharidosis (MPS) mouse models. In the MPS brain, the primary lysosomal enzyme dysfunction leads to accumulation of primary glycosaminoglycans (GAGs) with gangliosides (GM2 and GM3) being the major secondary storage products. With a focus on the neuropathology, a time course experiment was conducted in MPS I, MPS IIIA, MPS VII (severe and attenuated models) in order to understand the relative timing and level of GAG and ganglioside accumulation and how this correlates to behaviour deficits. Time course analysis from 1 to 6 months of age was conducted on brain samples to assess primary GAG (uronic acid), ß-hexosaminidase enzyme activity and levels of GM2 and GM3 gangliosides. This was compared to a battery of non-invasive behaviour tests including open field, inverted grid, rotarod and water cross maze were assessed to determine effects on motor function, activity and learning ability. The results show that the GAG and ganglioside accumulation begins prior to the onset of detectable changes in learning ability and behaviour. Interestingly, the highest levels of GAG and ganglioside accumulation was observed in the MPS IIIA mouse despite having 3% residual enzyme activity. Deficits in motor function were clearly observed in the severe Gusmps/mps, which were significantly delayed in the attenuated Gustm(L175F)Sly model despite their minimal increase in detectable enzyme activity. This suggests that genotype and residual enzyme activity are not indicative of severity of disease pathology in MPS disease and there exists a window when there are considerable storage products without detectable functional deficits which may allow an alteration to occur with therapy.

Structural characteristics of Medicago Sativa L. Polysaccharides and Se-modified polysaccharides as well as their antioxidant and neuroprotective activities.

Medicago Sativa L., a nutrient-rich plant used as feed for cattle and sheep, is widely planted globally. This study investigated the structural characteristics and activities of three kinds of novel polysaccharides (APS1, APS2 and APS3) isolated from the stems of M. sativa as well as its two selenium modified products (Se-APS2 and Se-APS3). APS1 (Mw = 13.4 KDa) and APS2 (Mw = 11.2 KDa) were composed of rhamnose, arabinose, mannose and galactose with different molar ratio, APS3 (Mw = 18.6 KDa) was composed of rhamnose, arabinose, fructose, mannose and galactose. All APS1-3 contained 1 â†’ 3 : 1 â†’ 6 : 1 â†’ 4 : 1 â†’ 2 glycosidic bonds in a ratio of 0.74:0.09:0.05:0.12, 0.34:0.20:0.36:0.10 and 0.63:0.17:0.06:0.14, respectively. The selenium content of Se-APS2 (Mw = 9.0 KDa) and Se-APS3 (Mw = 10.2 KDa) were 1.05 and 2.57 µg/mg, respectively. Their surface morphology and thermal stability were determined by scanning electron microscope (SEM) and thermal analysis (TGA), respectively. Further, the antioxidant and neuroprotective activities of the three natural polysaccharides and two Se-polysaccharides were studied. Interestingly, Se-polysaccharides not only exhibited higher antioxidant activity, but also higher neuroprotective activity compared to natural polysaccharides.

The nuclear receptor corepressor NCoR1 regulates hematopoiesis and leukemogenesis in vivo.

Enhanced understanding of normal and malignant hematopoiesis pathways should facilitate the development of effective clinical treatment strategies for hematopoietic malignancies. Nuclear receptor corepressor 1 (NCoR1) has been implicated in transcriptional repression and embryonic organ development, but its role in hematopoiesis is yet to be fully elucidated. Here, we showed that hematopoietic-specific loss of NCoR1 leads to expansion of the hematopoietic stem cell (HSC) pool due to aberrant cell cycle entry of long-term HSCs under steady-state conditions. Moreover, NCoR1-deficient HSCs exhibited normal self-renewal capacity but severely impaired lymphoid-differentiation potential in competitive hematopoietic-reconstitution assays. Transcriptome analysis further revealed that several hematopoiesis-associated genes are regulated by NCoR1. In addition, NCoR1 deficiency in hematopoietic cells delayed the course of leukemia and promoted leukemia cell differentiation in an MLL-AF9-induced mouse model. NCoR1 and its partner, histone deacetylase 3, can modulate histone acetylation and gene transcription through binding the promoter regions of myeloid-differentiation genes. Our collective results support the critical involvement of NCoR1 in normal and malignant hematopoiesis in vivo.

MLL5 suppresses antiviral innate immune response by facilitating STUB1-mediated RIG-I degradation.

Trithorax group protein MLL5 is an important epigenetic modifier that controls cell cycle progression, chromatin architecture maintenance, and hematopoiesis. However, whether MLL5 has a role in innate antiviral immunity is largely unknown. Here we show that MLL5 suppresses the RIG-I-mediated anti-viral immune response. Mll5-deficient mice infected with vesicular stomatitis virus show enhanced anti-viral innate immunity, reduced morbidity, and viral load. Mechanistically, a fraction of MLL5 located in the cytoplasm interacts with both RIG-I and its E3 ubiquitin ligase STUB1, which promotes K48-linked polyubiquitination and proteasomal degradation of RIG-I. MLL5 deficiency attenuates the RIG-I and STUB1 association, reducing K48-linked polyubiquitination and accumulation of RIG-I protein in cells. Upon virus infection, nuclear MLL5 protein translocates from the nucleus to the cytoplasm inducing STUB1-mediated degradation of RIG-I. Our study uncovers a previously unrecognized role for MLL5 in antiviral innate immune responses and suggests a new target for controlling viral infection.

The chromatin remodeling subunit Baf200 promotes normal hematopoiesis and inhibits leukemogenesis.

BACKGROUND: Adenosine triphosphate (ATP)-dependent chromatin remodeling SWI/SNF-like BAF and PBAF complexes have been implicated in the regulation of stem cell function and cancers. Several subunits of BAF or PBAF, including BRG1, BAF53a, BAF45a, BAF180, and BAF250a, are known to be involved in hematopoiesis. Baf200, a subunit of PBAF complex, plays a pivotal role in heart morphogenesis and coronary artery angiogenesis. However, little is known on the importance of Baf200 in normal and malignant hematopoiesis. METHODS: Utilizing Tie2-Cre-, Vav-iCre-, and Mx1-Cre-mediated Baf200 gene deletion combined with fetal liver/bone marrow transplantation, we investigated the function of Baf200 in fetal and adult hematopoiesis. In addition, a mouse model of MLL-AF9-driven leukemogenesis was used to study the role of Baf200 in malignant hematopoiesis. We also explored the potential mechanism by using RNA-seq, RT-qPCR, cell cycle, and apoptosis assays. RESULTS: Tie2-Cre-mediated loss of Baf200 causes perinatal death due to defective erythropoiesis and impaired hematopoietic stem cell expansion in the fetal liver. Vav-iCre-mediated loss of Baf200 causes only mild anemia and enhanced extramedullary hematopoiesis. Fetal liver hematopoietic stem cells from Tie2-Cre + , Baf200 f/f or Vav-iCre + , Baf200 f/f embryos and bone marrow hematopoietic stem cells from Vav-iCre + , Baf200 f/f mice exhibited impaired long-term reconstitution potential in vivo. A cell-autonomous requirement of Baf200 for hematopoietic stem cell function was confirmed utilizing the interferon-inducible Mx1-Cre mouse strain. Transcriptomes analysis revealed that expression of several erythropoiesis- and hematopoiesis-associated genes were regulated by Baf200. In addition, loss of Baf200 in a mouse model of MLL-AF9-driven leukemogenesis accelerates the tumor burden and shortens the host survival. CONCLUSION: Our current studies uncover critical roles of Baf200 in both normal and malignant hematopoiesis and provide a potential therapeutic target for suppressing the progression of leukemia without interfering with normal hematopoiesis.

Complement component C3a plays a critical role in endothelial activation and leukocyte recruitment into the brain.

BACKGROUND: The complement system is becoming increasingly recognized as a key participant in many neurodegenerative diseases of the brain. Complement-deficient animals exhibit reduced neuroinflammation. METHODS: In the present study, we administered intracerebroventricularly lipopolysaccharide (LPS) to mimic local infection of the brain and investigated the role of key complement component C3 in brain vasculature endothelial activation and leukocyte recruitment. The degree of neutrophil infiltration was determined by esterase staining. Leukocyte-endothelial interactions were measured using intravital microscopy. Cerebral endothelial activation was evaluated using real-time PCR and Western blotting. RESULTS: Neutrophil infiltration into the brain cortex and hippocampus was significantly reduced in C3(-/-) mice and C3aR(-/-) mice but not in C6(-/-) mice. We detected markedly attenuated leukocyte-endothelial interactions in the brain microvasculature of C3(-/-) mice. Accordingly, in response to LPS administration, the brain microvasculature in these mice had decreased expression of P-selectin, E-selectin, intercellular cell adhesion molecule 1 (ICAM-1), and vascular cell adhesion molecule 1 (VCAM-1). Depletion of C3 from the circulation also caused reduction in VCAM-1 and E-selectin expression and leukocyte recruitment, suggesting that C3 in the circulation contributed to brain endothelial activation. Furthermore, C3(-/-) mice exhibited decreased leukocyte recruitment into the brain upon tumor necrosis factor-α (TNF-α) stimulation. C3a activated the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) and induced the upregulation of VCAM-1 and ICAM-1 expression in murine primary cerebral endothelial cells in vitro. CONCLUSIONS: Our study provides the first evidence that C3a plays a critical role in cerebral endothelial activation and leukocyte recruitment during inflammation in the brain.

Mixed Lineage Leukemia 5 (MLL5) Protein Stability Is Cooperatively Regulated by O-GlcNac Transferase (OGT) and Ubiquitin Specific Protease 7 (USP7).

Mixed lineage leukemia 5 (MLL5) protein is a trithorax family histone 3 lysine 4 (H3K4) methyltransferase that regulates diverse biological processes, including cell cycle progression, hematopoiesis and cancer. The mechanisms by which MLL5 protein stability is regulated have remained unclear to date. Here, we showed that MLL5 protein stability is cooperatively regulated by O-GlcNAc transferase (OGT) and ubiquitin-specific protease 7 (USP7). Depletion of OGT in cells led to a decrease in the MLL5 protein level through ubiquitin/proteasome-dependent proteolytic degradation, whereas ectopic expression of OGT protein suppressed MLL5 ubiquitylation. We further identified deubiquitinase USP7 as a novel MLL5-associated protein using mass spectrometry. USP7 stabilized the MLL5 protein through direct binding and deubiquitylation. Loss of USP7 induced degradation of MLL5 protein. Conversely, overexpression of USP7, but not a catalytically inactive USP7 mutant, led to decreased ubiquitylation and increased MLL5 stability. Co-immunoprecipitation and co-immunostaining assays revealed that MLL5, OGT and USP7 interact with each other to form a stable ternary complex that is predominantly located in the nucleus. In addition, upregulation of MLL5 expression was correlated with increased expression of OGT and USP7 in human primary cervical adenocarcinomas. Our results collectively reveal a novel molecular mechanism underlying regulation of MLL5 protein stability and provide new insights into the functional interplay among O-GlcNAc transferase, deubiquitinase and histone methyltransferase.

Mll2 controls cardiac lineage differentiation of mouse embryonic stem cells by promoting H3K4me3 deposition at cardiac-specific genes.

Trithorax group (TrxG) proteins play critical roles in transcriptional activation by promoting methylation of histone H3 Lysine 4 (H3K4), but the precise functions of the individual TrxG members during embryonic differentiation are not fully understood. Here we show that Mll2, a TrxG member, is required for proliferation but is dispensable for maintaining the pluripotency of mouse embryonic stem cells (ESCs). In addition, differentiation of ESCs toward mesodermal and endodermal lineages is severely altered and, in particular, the cardiac lineage differentiation of ESCs is completely abolished in the absence of Mll2. Moreover, the expression of core cardiac transcription factors and the levels of H3K4 tri-methylation of these cardiac-specific promoters are significantly decreased by the loss of Mll2. Taken together, our results reveal a critical role for Mll2 in proliferation and cardiac lineage differentiation of mouse ESCs, and provide novel molecular insight into the mechanisms of cardiac development and disease.

Mixed lineage leukemia 5 (MLL5) protein regulates cell cycle progression and E2F1-responsive gene expression via association with host cell factor-1 (HCF-1).

Trithorax group proteins methylate lysine 4 of histone 3 (H3K4) at active gene promoters. MLL5 protein, a member of the Trithorax protein family, has been implicated in the control of the cell cycle progression; however, the underlying molecular mechanism(s) have not been fully determined. In this study, we found that the MLL5 protein can associate with the cell cycle regulator "host cell factor" (HCF-1). The interaction between MLL5 and HCF-1 is mediated by the "HCF-1 binding motif" (HBM) of the MLL5 protein and the Kelch domain of the HCF-1 protein. Confocal microscopy showed that the MLL5 protein largely colocalized with HCF-1 in the nucleus. Knockdown of MLL5 resulted in reduced cell proliferation and cell cycle arrest in the G1 phase. Moreover, down-regulation of E2F1 target gene expression and decreased H3K4me3 levels at E2F1-responsive promoters were observed in MLL5 knockdown cells. Additionally, the core subunits, including ASH2L, RBBP5, and WDR5, that are necessary for effective H3K4 methyltransferase activities of the Trithorax protein complexes, were absent in the MLL5 complex, suggesting that a distinct mechanism may be used by MLL5 for exerting its H3K4 methyltransferase activity. Together, our findings demonstrate that MLL5 could associate with HCF-1 and then be recruited to E2F1-responsive promoters to stimulate H3K4 trimethylation and transcriptional activation, thereby facilitating the cell cycle G1 to S phase transition.