Apoptosis is a common pathway that finally mediated the killing functions of anticancer drugs, which is an important cause of multidrug resistance (MDR). The aim of this study was to investigate the potential benefit of combination therapy with magnetic nanoparticle of Fe(3)O(4) (MNP(Fe(3)O(4))) and 5-bromotetrandrin (BrTet). Analysis of the apoptosis percentage showed that combination of daunorubicin (DNR) with either MNP(Fe(3)O(4)) or BrTet exerted a potent cytotoxic effect on K562/A02 cells, while MNP(Fe(3)O(4)) and BrTet cotreatment can synergistically enhance DNR-induced apoptosis. Importantly, we confirmed that the distinct synergism effect of that composite on reverse multidrug resistance may owe to the regulation of various proliferative and antiapoptotic gene products, including P53 and caspase-3. Thus our in vitro data strongly suggests a potential clinical application of MNP(Fe(3)O(4)) and BrTet combination on CML.

Oxidative stress is an important contributor to cancer development. Consistent with that, antioxidant enzymes have been demonstrated to suppress tumorigenesis when being elevated both in vitro and in vivo, making induction of these enzymes a more potent approach for cancer prevention. Protandim, a well-defined combination of widely studied medicinal plants, has been shown to induce superoxide dismutase (SOD) and catalase activities and reduce superoxide generation and lipid peroxidation in healthy human subjects. To investigate whether Protandim can suppress tumor formation by a dietary approach, a two-stage mouse skin carcinogenesis study was performed. At the end of the study, the mice on a Protandim-containing basal diet had similar body weight compared with those on the basal diet, which indicated no overt toxicity by Protandim. After three weeks on the diets, there was a significant increase in the expression levels of SOD and catalase, in addition to the increases in SOD activities. Importantly, at the end of the carcinogenesis study, both skin tumor incidence and multiplicity were reduced in the mice on the Protandim diet by 33% and 57% respectively, compared with those on basal diet. Biochemical and histological studies revealed that the Protandim diet suppressed tumor promoter-induced oxidative stress (evidenced by reduction of protein carbonyl levels), cell proliferation (evidenced by reduction of skin hyperplasia and suppression of PKC/JNK/Jun pathway), and inflammation (evidenced by reduction of ICAM-1/VCAM-1 expression, NF-kappaB binding activity, and nuclear p65/p50 levels). Overall, induction of antioxidant enzymes by Protandim may serve as a practical and potent approach for cancer prevention.

The X protein (HBx) of hepatitis B virus (HBV) is involved in the development of hepatocellular carcinoma (HCC), and methionine adenosyltransferase 2A (MAT2A) promotes the growth of liver cancer cells through altering S-adenosylmethionine homeostasis. Thus, we speculated that a link between HBx and MAT2A may contribute to HCC development. In this study, the effects of HBx on MAT2A expression and cell apoptosis were investigated, and the molecular mechanism by which HBx and MAT2A regulate tumorigenesis was evaluated. Results from immunohistochemistry analyses of 37 pairs of HBV-associated liver cancer tissues/corresponding peritumor tissues showed that HBx and MAT2A are highly expressed in most liver tumor tissues. Our in vitro results revealed that HBx activates MAT2A expression in a dose-dependent manner in hepatoma cells, and such regulation requires the cis-regulatory elements NF-κB and CREB on the MAT2A gene promoter. Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) further demonstrated that HBx facilitates the binding of NF-κB and CREB to MAT2A gene promoter. In addition, overexpression of HBx or MAT2A inhibits cell apoptosis, whereas knockdown of MAT2A expression stimulates apoptosis in hepatoma cells. Furthermore, we demonstrated that HBx reduces MAT1A expression and AdoMet production but enhances MAT2β expression. Thus, we proposed that HBx activates MAT2A expression through NF-κB and CREB signaling pathways to reduce AdoMet production, inhibit hepatoma cell apoptosis, and perhaps enhance HCC development. These findings should provide new insights into our understanding how the molecular mechanisms underline the effects of HBV infection on the production of MAT2A and the development of HCC.

Polycomb group proteins are critical to maintaining gene repression established during Drosophila development. Part of this group forms the PRC2 complex containing Ez that catalyzes di- and trimethylation of histone H3 lysine 27 (H3K37me2/3), marks repressive to transcription. We report that the mammalian homologs Ezh1 and Ezh2 form similar PRC2 complexes but exhibit contrasting repressive roles. While PRC2-Ezh2 catalyzes H3K27me2/3 and its knockdown affects global H3K27me2/3 levels, PRC2-Ezh1 performs this function weakly. In accordance, Ezh1 knockdown was ineffectual on global H3K27me2/3 levels. Instead, PRC2-Ezh1 directly and robustly represses transcription from chromatinized templates and compacts chromatin in the absence of the methyltransferase cofactor SAM, as evidenced by electron microscopy. Ezh1 targets a subset of Ezh2 genes, yet Ezh1 is more abundant in nonproliferative adult organs while Ezh2 expression is tightly associated with proliferation, as evidenced when analyzing aging mouse kidney. These results might reflect subfunctionalization of a PcG protein during evolution.

Studies have begun to focus on the emerging function of platelets as immune and inflammatory cells that initiate and accelerate vascular inflammation. Phosphoinositide 3-kinase gamma (PI3Kγ) is critically involved in a number of inflammatory and autoimmune diseases. This study aims to investigate the contribution of platelet PI3Kγ to vascular remodeling under flow severely reduced conditions. Mouse partial left carotid artery ligation with adoptive transfer of activated, washed wild-type or PI3Kγ-/- platelets was used as the model. Intima-media area, leukocyte recruitment, and proinflammatory mediator expression were assessed. In vitro PI3Kγ-/- platelets were used to verify the effect of PI3Kγ on platelet activation, interaction with leukocytes, and endothelial cells. Mice injected with activated platelets showed a significant increase in intima-media thickening, recruitment of neutrophils (at 3 d) and macrophages (at 21 d), and intercellular adhesion molecule-1, vascular cell adhesion molecule-1, tumor necrosis factor alpha, and interleukin-6 expression (at 3 d) in the flow-reduced area. These effects were abrogated by platelet PI3Kγ deficiency. Circulating platelet-leukocyte aggregates were reduced in PI3Kγ-/- mice after partial ligation. In vivo data confirmed that PI3Kγ mediated Adenine di-Phosphate -induced platelet activation through the Akt and p38 MAP kinase signaling pathways. Moreover, platelet PI3Kγ deficiency reduced platelet-leukocyte aggregation and platelet-endothelial cell (EC) interaction. These findings indicate that platelet PI3Kγ contributes to platelet-mediated vascular inflammation and carotid intima-media thickening after flow severely reduced. Platelet PI3Kγ may be a new target in the treatment of vascular diseases.

The H3 histone variant CENP-A is an epigenetic marker critical for the centromere identity and function. However, the precise regulation of the spatiotemporal deposition and propagation of CENP-A at centromeres during the cell cycle is still poorly understood. Here, we show that CENP-A is phosphorylated at Ser68 during early mitosis by Cdk1. Our results demonstrate that phosphorylation of Ser68 eliminates the binding of CENP-A to the assembly factor HJURP, thus preventing the premature loading of CENP-A to the centromere prior to mitotic exit. Because Cdk1 activity is at its minimum at the mitotic exit, the ratio of Cdk1/PP1α activity changes in favor of Ser68 dephosphorylation, thus making CENP-A available for centromeric deposition by HJURP. Thus, we reveal that dynamic phosphorylation of CENP-A Ser68 orchestrates the spatiotemporal assembly of newly synthesized CENP-A at active centromeres during the cell cycle.

Human cytomegalovirus (hCMV) immediate early 1 (IE1) protein associates with condensed chromatin of the host cell during mitosis. We have determined the structure of the chromatin-tethering domain (CTD) of IE1 bound to the nucleosome core particle, and discovered that IE1-CTD specifically interacts with the H2A-H2B acidic patch and impairs the compaction of higher-order chromatin structure. Our results suggest that IE1 loosens up the folding of host chromatin during hCMV infections.

Coactosin-like protein 1 (Cotl1), a member of the actin-depolymerizing factor (ADF)/cofilin family, was first purified from a soluble fraction of Dictyostelium discoideum cells. Neuronal migration requires cytoskeletal remodeling and actin regulation. Although Cotl1 strongly binds to F-actin, the role of Cotl1 in neuronal migration remains undescribed. In this study, we revealed that Cotl1 overexpression impaired migrationof both early- and late-born neurons during mouse corticogenesis. Moreover, Cotl1 overexpression delayed, rather than blocked, neuronal migration in late-born neurons. Cotl1 expression disturbed the morphology of migrating neurons, lengthening the leading processes. This study is the first to investigate the function of Cotl1, and the results indicate that Cotl1 is involved in the regulation of neuronal migration and morphogenesis.

H3.3 is an ancient and conserved H3 variant and plays essential roles in transcriptional regulation. HIRA complex, which is composed of HIRA, UBN1 or UBN2, and Cabin1, is a H3.3 specific chaperone complex. However, it still remains largely uncharacterized how HIRA complex specifically recognizes and deposits H3.3 to the chromatin, such as promoters and enhancers.

Wnt signaling is essential for the maintenance of adult stem cells and its aberrant activation is a stimulator of carcinogenesis. The transmembrane protein, Wntless, is an essential Wnt signaling component through regulating the secretion of Wnt ligands. Here, we generated a mouse model with specific Wntless knockout in intestinal epithelium to study its function in the intestinal epithelium. Wntless knockout exhibits no obvious defects in mice but significantly disrupted proliferation and differentiation of small intestinal organoids. We also discovered that these deficiencies could be partially rescued by Wnt3a supplement but not Wnt9b. To further investigate the role of Wntless in tumorigenesis, APC-deficient spontaneous intestinal tumors and chemical induced colorectal cancer mouse models were employed. To our surprise, intestinal epithelium-specific knockout of Wntless did not cause significant differences in tumor number and size. In summary, our data demonstrated that epithelial Wntless was required for the growth and differentiation of small intestinal organoids but not in live animals, suggesting the other tissues, such as mesenchymal tissue, play critical role for Wnt secretion in both intestinal homeostasis as well as tumorigenesis.

Evodiamine (EVO) is a natural compound derived from Tetradium ruticarpum (A.Juss.) T.G.Hartley used to treat pain and migraine in traditional Chinese medicine. EVO is the primary active ingredient of Tetradium ruticarpum. However, the preventive effect of EVO against migraine remains unexplored.

Chromatin dynamics play a critical role in cell fate determination and maintenance by regulating the expression of genes essential for development and differentiation. In mouse embryonic stem cells (mESCs), maintenance of pluripotency coincides with a poised chromatin state containing active and repressive histone modifications. However, the structural features of poised chromatin are largely uncharacterized. By adopting mild time-course MNase-seq with computational analysis, the low-compact chromatin in mESCs is featured in two groups: one in more open regions, corresponding to an active state, and the other enriched with bivalent histone modifications, considered the poised state. A parameter called the chromatin opening potential index (COPI) is also devised to quantify the transcription potential based on the dynamic changes of MNase-seq signals at promoter regions. Use of COPI provides effective prediction of gene activation potential and, more importantly, reveals a few developmental factors essential for mouse neural progenitor cell (NPC) differentiation.

Metazoan cells only utilize a small subset of the potential DNA replication origins to duplicate the whole genome in each cell cycle. Origin choice is linked to cell growth, differentiation, and replication stress. Although various genetic and epigenetic signatures have been linked to the replication efficiency of origins, there is no consensus on how the selection of origins is determined.

Phosphoinositide 3-kinase beta (PI3Kβ) plays an important role in platelet activation and thrombosis, but its role in stroke pathology remains unknown. In this study, we investigated whether inhibition of PI3Kβ protects against cerebral ischemia/reperfusion (I/R) injury by preventing circulating platelet activation and downstream microvascular thrombosis. We used a rat intraluminal filament model of transient middle cerebral artery occlusion (tMCAO) because the rapid restoration of cerebral blood flow to the ischemic area in both tMCAO and endovascular thrombectomy provides clinical relevance for this model. The results showed that TGX221, a selective PI3Kβ inhibitor, treatment immediately before the onset of reperfusion dose-dependently reduced infarct volume and improved neurological function. The protective effects were associated with blocking platelet activation and thrombotic response, thereby reducing downstream microvascular thrombosis, and maintaining reperfusion efficiency. These results suggest that PI3Kβ might be a promising target for treating downstream microvascular thrombosis induced by cerebral I/R injury and offer a novel adjunctive treatment to improve reperfusion therapy for acute ischemic stroke.

DNA replication ensures the accurate transmission of genetic information during the cell cycle. Histone variant H2A.Z is crucial for early replication origins licensing and activation in which SUV420H1 preferentially recognizes H2A.Z-nucleosome and deposits H4 lysine 20 dimethylation (H4K20me2) on replication origins. Here, we report the cryo-EM structures of SUV420H1 bound to H2A.Z-nucleosome or H2A-nucleosome and demonstrate that SUV420H1 directly interacts with H4 N-terminal tail, the DNA, and the acidic patch in the nucleosome. The H4 (1-24) forms a lasso-shaped structure that stabilizes the SUV420H1-nucleosome complex and precisely projects the H4K20 residue into the SUV420H1 catalytic center. In vitro and in vivo analyses reveal a crucial role of the SUV420H1 KR loop (residues 214-223), which lies close to the H2A.Z-specific residues D97/S98, in H2A.Z-nucleosome preferential recognition. Together, our findings elucidate how SUV420H1 recognizes nucleosomes to ensure site-specific H4K20me2 modification and provide insights into how SUV420H1 preferentially recognizes H2A.Z nucleosome.

Lysine succinylation is one of the major post-translational modifications occurring on histones and is believed to have significant roles in regulating chromatin structure and function. Currently, histone desuccinylation is widely believed to be catalyzed by members of the SIRT family deacetylases. Here, we report that histone desuccinylation is in fact primarily catalyzed by the class I HDAC1/2/3. Inhibition or depletion of HDAC1/2/3 resulted in a marked increase of global histone succinylation, whereas ectopic expression of HDAC1/2/3 but not their deacetylase inactive mutants downregulated global histone succinylation. We demonstrated that the class I HDAC1/2/3 complexes have robust histone desuccinylase activity in vitro. Genomic landscape analysis revealed that histone succinylation is highly enriched at gene promoters and inhibition of HDAC activity results in marked elevation of promoter histone succinylation. Furthermore, our integrated analysis revealed that promoter histone succinylation positively correlates with gene transcriptional activity. Collectively, we demonstrate that the class I HDAC1/2/3 but not the SIRT family proteins are the major histone desuccinylases particularly important for promoter histone desuccinylation. Our study thus sheds new light on the role of histone succinylation in transcriptional regulation.

The chromatin-based rule governing the selection and activation of replication origins in metazoans remains to be investigated. Here we report that NFIB, a member of Nuclear Factor I (NFI) family that was initially purified in host cells to promote adenoviral DNA replication but has since mainly been investigated in transcription regulation, is physically associated with the pre-replication complex (pre-RC) in mammalian cells. Genomic analyses reveal that NFIB facilitates the assembly of the pre-RC by increasing chromatin accessibility. Nucleosome binding and single-molecule magnetic tweezers shows that NFIB binds to and opens up nucleosomes. Transmission electron microscopy indicates that NFIB promotes nucleosome eviction on parental chromatin. NFIB deficiency leads to alterations of chromosome contacts/compartments in both G1 and S phase and affects the firing of a subset of origins at early-replication domains. Significantly, cancer-associated NFIB overexpression provokes gene duplication and genomic alterations recapitulating the genetic aberrance in clinical breast cancer and empowering cancer cells to dynamically evolve growth advantage and drug resistance. Together, these results point a role for NFIB in facilitating replication licensing by acting as a genome organizer, shedding new lights on the biological function of NFIB and on the replication origin selection in eukaryotes.

The major enhancer regulator lysine-specific histone demethylase 1A (LSD1) is required for mammalian embryogenesis and is implicated in human congenital diseases and multiple types of cancer; however, the underlying mechanisms remain enigmatic. Here, we dissect the role of LSD1 and its demethylase activity in gene regulation and cell fate transition. Surprisingly, the catalytic inactivation of LSD1 has a mild impact on gene expression and cellular differentiation whereas the loss of LSD1 protein de-represses enhancers globally and impairs cell fate transition. LSD1 deletion increases H3K27ac levels and P300 occupancy at LSD1-targeted enhancers. The gain of H3K27ac catalyzed by P300/CBP, not the loss of CoREST complex components from chromatin, contributes to the transcription de-repression of LSD1 targets and differentiation defects caused by LSD1 loss. Together, our study demonstrates a demethylase-independent role of LSD1 in regulating enhancers and cell fate transition, providing insight into treating diseases driven by LSD1 mutations and misregulation.

Whole-genome duplication (WGD), or polyploidy, events are widespread and significant in the evolutionary history of angiosperms. However, empirical evidence for rediploidization, the major process where polyploids give rise to diploid descendants, is still lacking at the genomic level. Here we present chromosome-scale genomes of the mangrove tree Sonneratia alba and the related inland plant Lagerstroemia speciosa. Their common ancestor has experienced a whole-genome triplication (WGT) approximately 64 million years ago coinciding with a period of dramatic global climate change. Sonneratia, adapting mangrove habitats, experienced extensive chromosome rearrangements post-WGT. We observe the WGT retentions display sequence and expression divergence, suggesting potential neo- and sub-functionalization. Strong selection acting on three-copy retentions indicates adaptive value in response to new environments. To elucidate the role of ploidy changes in genome evolution, we improve a model of the polyploidization-rediploidization process based on genomic evidence, contributing to the understanding of adaptive evolution during climate change.

No abstract available