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DNA double-strand breaks (DSBs) are repaired by either the homology-directed repair (HDR) or the non-homologous end-joining (NHEJ) pathway. RIF1 (RAP1-interacting factor homolog) was recently shown to stimulate NHEJ through an interaction with 53BP1 (p53-binding protein 1) phosphorylated at S/TQ sites, but the molecular mechanism underlying pathway choice remains unclear. Here, we show that SCAI (suppressor of cancer cell invasion) binds to 53BP1 phosphorylated at S/TP sites and facilitates HDR. Upon DNA damage, RIF1 immediately accumulates at damage sites and then gradually dissociates from 53BP1 and is subsequently replaced with SCAI. Depletion of SCAI reduces both the accumulation of HDR factors, including BRCA1 (breast cancer susceptibility gene 1), at damage sites and the efficiency of HDR, as detected by a reporter assay system. These data suggest that SCAI inhibits RIF1 function to allow BRCA1-mediated repair, which possibly includes alt-NHEJ and resection-dependent NHEJ in G1, as well as HDR in S/G2.

Human inactive X chromosome (Xi) forms a compact structure called the Barr body, which is enriched in repressive histone modifications such as trimethylation of histone H3 Lys9 (H3K9me3) and Lys27 (H3K27me3). These two histone marks are distributed in distinct domains, and X-inactive specific transcript (XIST) preferentially colocalizes with H3K27me3 domains. Here we show that Xi compaction requires HBiX1, a heterochromatin protein 1 (HP1)-binding protein, and structural maintenance of chromosomes hinge domain-containing protein 1 (SMCHD1), both of which are enriched throughout the Xi chromosome. HBiX1 localization to H3K9me3 and XIST-associated H3K27me3 (XIST-H3K27me3) domains was mediated through interactions with HP1 and SMCHD1, respectively. Furthermore, HBiX1 was required for SMCHD1 localization to H3K9me3 domains. Depletion of HBiX1 or SMCHD1, but not Polycomb repressive complex 2 (PRC2), resulted in Xi decompaction, similarly to XIST depletion. Thus, the molecular network involving HBiX1 and SMCHD1 links the H3K9me3 and XIST-H3K27me3 domains to organize the compact Xi structure.

Summary Polycomb repressor complexes (PRCs) are important chromatin modifiers fundamentally implicated in pluripotency and cancer. Polycomb silencing in embryonic stem cells (ESCs) can be accompanied by active chromatin and primed RNA polymerase II (RNAPII), but the relationship between PRCs and RNAPII remains unclear genome-wide. We mapped PRC repression markers and four RNAPII states in ESCs using ChIP-seq, and found that PRC targets exhibit a range of RNAPII variants. First, developmental PRC targets are bound by unproductive RNAPII (S5p+S7p−S2p−) genome-wide. Sequential ChIP, Ring1B depletion, and genome-wide correlations show that PRCs and RNAPII-S5p physically bind to the same chromatin and functionally synergize. Second, we identify a cohort of genes marked by PRC and elongating RNAPII (S5p+S7p+S2p+); they produce mRNA and protein, and their expression increases upon PRC1 knockdown. We show that this group of PRC targets switches between active and PRC-repressed states within the ESC population, and that many have roles in metabolism., Graphical Abstract Highlights ► A unique RNAPII variant (S5p+S7p−S2p−) binds PRC targets genome-wide in ESCs ► RNAPII-S5p and PRC coincide in time and localization, and show proportional abundance ► Novel, active PRC-target genes identified in ESCs include metabolic genes ► Active PRC targets switch between on/off (active/PRC) states in the ESC population

Histone acetylation is generally associated with gene activation and chromatin decondensation. Recent mass spectrometry analysis has revealed that histone H4 lysine 20, a major methylation site, can also be acetylated. To understand the function of H4 lysine 20 acetylation (H4K20ac), we have developed a specific monoclonal antibody and performed ChIP-seq analysis using HeLa-S3 cells. H4K20ac was enriched around the transcription start sites (TSSs) of minimally expressed genes and in the gene body of expressed genes, in contrast to most histone acetylation being enriched around the TSSs of expressed genes. The distribution of H4K20ac showed little correlation with known histone modifications, including histone H3 methylations. A motif search in H4K20ac-enriched sequences, together with transcription factor binding profiles based on ENCODE ChIP-seq data, revealed that most transcription activators are excluded from H4K20ac-enriched genes and a transcription repressor NRSF/REST co-localized with H4K20ac. These results suggest that H4K20ac is a unique acetylation mark associated with gene repression.

Histone modifications play an important role in epigenetic gene regulation and genome integrity. It remains largely unknown, however, how these modifications dynamically change in individual cells. By using fluorescently labeled specific antigen binding fragments (Fabs), we have developed a general method to monitor the distribution and global level of endogenous histone H3 lysine modifications in living cells without disturbing cell growth and embryo development. Fabs produce distinct nuclear patterns that are characteristic of their target modifications. H3K27 trimethylation-specific Fabs, for example, are concentrated on inactive X chromosomes. As Fabs bind their targets transiently, the ratio of bound and free molecules depends on the target concentration, allowing us to measure changes in global modification levels. High-affinity Fabs are suitable for mouse embryo imaging, so we have used them to monitor H3K9 and H3K27 acetylation levels in mouse preimplantation embryos produced by in vitro fertilization and somatic cell nuclear transfer. The data suggest that a high level of H3K27 acetylation is important for normal embryo development. As Fab-based live endogenous modification labeling (FabLEM) is broadly useful for visualizing any modification, it should be a powerful tool for studying cell signaling and diagnosis in the future.

Heterochromatin protein 1 (HP1) has an essential role in heterochromatin formation and mitotic progression through its interaction with various proteins. We have identified a unique HP1alpha-binding protein, POGZ (pogo transposable element-derived protein with zinc finger domain), using an advanced proteomics approach. Proteins generally interact with HP1 through a PxVxL (where x is any amino-acid residue) motif; however, POGZ was found to bind to HP1alpha through a zinc-finger-like motif. Binding by POGZ, mediated through its zinc-finger-like motif, competed with PxVxL proteins and destabilized the HP1alpha-chromatin interaction. Depletion experiments confirmed that the POGZ HP1-binding domain is essential for normal mitotic progression and dissociation of HP1alpha from mitotic chromosome arms. Furthermore, POGZ is required for the correct activation and dissociation of Aurora B kinase from chromosome arms during M phase. These results reveal POGZ as an essential protein that links HP1alpha dissociation with Aurora B kinase activation during mitosis.

A new technique illuminates differential H3S10 phosphorylation dynamics in normal and cancer cells; spatial and temporal regulation of this process by aurora B kinase is required for accurate chromosome segregation., Posttranslational histone modifications regulate both gene expression and genome integrity. Despite the dynamic nature of these modifications, appropriate real-time monitoring systems are lacking. In this study, we developed a method to visualize histone modifications in living somatic cells and preimplantation embryos by loading fluorescently labeled specific Fab antibody fragments. The technique was used to study histone H3 Ser10 (H3S10) phosphorylation, which occurs during chromosome condensation in mitosis mediated by the aurora B kinase. In aneuploid cancer cells that frequently missegregate chromosomes, H3S10 is phosphorylated just before the chromosomes condense, whereas aurora B already accumulates in nuclei during S phase. In contrast, in nontransformed cells, phosphorylated H3S10 foci appear for a few hours during interphase, and transient exposure to an aurora B–selective inhibitor during this period induces chromosome missegregation. These results suggest that, during interphase, moderate aurora B activity or H3S10 phosphorylation is required for accurate chromosome segregation. Visualizing histone modifications in living cells will facilitate future epigenetic and cell regulation studies.

The prevalence of smoking among Japanese nurses, specially in their twenties, is higher than that among the general female population. To examine smoking behavior, smoking initiating and cessation factors, we conducted a cohort study through questionnaire survey, targeting nurses (n=1572) working at 11 hospitals located in Tokyo metropolitan area. The first survey was conducted using a confidential questionnaire on smoking, followed by a second survey conducted in the same manner on the same subjects two years later. As to smoking status after two years, 8% (95%CI=1.5%) started smoking and 6% (95%CI=1.4%) quitted resulting in a 2% increase in the prevalence of current smoking. The average nicotine dependence for nurses who were smokers in the two surveys rose from 3.9 to 4.3 (P

Statins exert atheroprotective effects through the induction of specific transcriptional factors in multiple organs. In endothelial cells, statin-dependent atheroprotective gene up-regulation is mediated by Kruppel-like factor (KLF) family transcription factors. To dissect the mechanism of gene regulation, we sought to determine molecular targets by performing microarray analyses of human umbilical vein endothelial cells (HUVECs) treated with pitavastatin, and KLF4 was determined to be the most highly induced gene. In addition, it was revealed that the atheroprotective genes induced with pitavastatin, such as nitric oxide synthase 3 (NOS3) and thrombomodulin (THBD), were suppressed by KLF4 knockdown. Myocyte enhancer factor-2 (MEF2) family activation is reported to be involved in pitavastatin-dependent KLF4 induction. We focused on MEF2C among the MEF2 family members and identified a novel functional MEF2C binding site 148 kb upstream of the KLF4 gene by chromatin immunoprecipitation along with deep sequencing (ChIP-seq) followed by luciferase assay. By applying whole genome and quantitative chromatin conformation analysis {chromatin interaction analysis with paired end tag sequencing (ChIA-PET), and real time chromosome conformation capture (3C) assay}, we observed that the MEF2C-bound enhancer and transcription start site (TSS) of KLF4 came into closer spatial proximity by pitavastatin treatment. 3D-Fluorescence in situ hybridization (FISH) imaging supported the conformational change in individual cells. Taken together, dynamic chromatin conformation change was shown to mediate pitavastatin-responsive gene induction in endothelial cells.

Photobrightening of photodarkened CdS- and CdS x Se1 - x -doped glasses was investigated using luminescence and electron spin resonance (ESR). Photobrightening depends on wavelength of laser light, and it is observed in all samples investigated, when wavelength of laser light is longer than that of absorption edge. Photobrightening depends on glass composition.

To optimize live cell fluorescence imaging, the choice of fluorescent substrate is a critical factor. Although genetically encoded fluorescent proteins have been used widely, chemical fluorescent dyes are still useful when conjugated to proteins or ligands. However, little information is available for the suitability of different fluorescent dyes for live imaging. We here systematically analyzed the property of a number of commercial fluorescent dyes when conjugated with antigen-binding (Fab) fragments directed against specific histone modifications, in particular, phosphorylated H3S28 (H3S28ph) and acetylated H3K9 (H3K9ac). These Fab fragments were conjugated with a fluorescent dye and loaded into living HeLa cells. H3S28ph-specific Fab fragments were expected to be enriched in condensed chromosomes, as H3S28 is phosphorylated during mitosis. However, the degree of Fab fragment enrichment on mitotic chromosomes varied depending on the conjugated dye. In general, green fluorescent dyes showed higher enrichment, compared to red and far-red fluorescent dyes, even when dye∶protein conjugation ratios were similar. These differences are partly explained by an altered affinity of Fab fragment after dye-conjugation; some dyes have less effect on the affinity, while others can affect it more. Moreover, red and far-red fluorescent dyes tended to form aggregates in the cytoplasm. Similar results were observed when H3K9ac-specific Fab fragments were used, suggesting that the properties of each dye affect different Fab fragments similarly. According to our analysis, conjugation with green fluorescent dyes, like Alexa Fluor 488 and Dylight 488, has the least effect on Fab affinity and is the best for live cell imaging, although these dyes are less photostable than red fluorescent dyes. When multicolor imaging is required, we recommend the following dye combinations for optimal results: Alexa Fluor 488 (green), Cy3 (red), and Cy5 or CF640 (far-red).

To prevent osteoporosis, which is expected to increase in incidence in this rapidly aging society, in recent years bone mineral density (BMD) has frequently been measured as a predisposition index. However, these measurements are made on different sites with different apparatus, and the results are independently studied by different institutions. In our present investigation, to establish the standard radius BMD as determined by dual-energy X-ray absorptiometry (DXA), we carried out a general population survey in 29 municipalities and prefectures on 11,252 locally residing females aged 15 to 83 years (mean, 35.61 +/- 12.85 years). Their YAM (young adult mean) BMD was estimated at 0.664 +/- 0.054 g/cm2, which was almost the same as the figure given in the 1996 version of the diagnostic criteria for primary osteoporosis. We further studied the relationships of BMD to age and physical factors known to be influential to BMD. It was found that BMD was correlated negatively to age and positively to body mass index (BMI). The average values we obtained for age and physique groups appeared to have provided reliable indices for the primary prevention of osteoporosis.

Post-translational histone modifications play key roles in gene regulation, development, and differentiation, but their dynamics in living organisms remain almost completely unknown. To address this problem, we developed a genetically encoded system for tracking histone modifications by generating fluorescent modification-specific intracellular antibodies (mintbodies) that can be expressed in vivo. To demonstrate, an H3 lysine 9 acetylation specific mintbody (H3K9ac-mintbody) was engineered and stably expressed in human cells. In good agreement with the localization of its target acetylation, H3K9ac-mintbody was enriched in euchromatin, and its kinetics measurably changed upon treatment with a histone deacetylase inhibitor. We also generated transgenic fruit fly and zebrafish stably expressing H3K9ac-mintbody for in vivo tracking. Dramatic changes in H3K9ac-mintbody localization during Drosophila embryogenesis could highlight enhanced acetylation at the start of zygotic transcription around mitotic cycle 7. Together, this work demonstrates the broad potential of mintbody and lays the foundation for epigenetic analysis in vivo.

Topoisomerase II (topo II) separates chromosomes at the end of mitosis and is also the target for various chemotherapeutic agents. Expression of this enzyme has been demonstrated to increase rapidly at the end of the S to G2/M phase and decrease after the completion of mitosis. We immunolocalized topo II in specimens of both normal and neoplastic human gastric mucosas to evaluate expression of this enzyme. Three different antibodies were used for the immunostaining of topo II (anti-topo II alpha isoform, anti-topo II beta isoform and anti-topo II alpha and -beta isoforms). There were no significant differences in topo II labeling index (LI) between frozen and paraffin-embedded tissue sections obtained from the same cases. Topo II LI was significantly correlated with Ki67 LI in all of the specimens examined. The area of cells positive for Topo II was much narrower than that of Ki67 in the normal gastric glands, and the pattern of Topo II immunolocalization in both adenomas and adenocarcinomas was also essentially the same as that of Ki67. The topo II LI values (positive cells/1000 cells) for normal gastric gland, adenoma, intestinal-type adenocarcinoma, and diffuse-type adenocarcinoma were 114.7 +/- 2.2, 266.7 +/- 18.8, 277.6 +/- 19.2, and 324.5 +/- 5.3, respectively. Significant differences in topo II LI and topo II/Ki67 index were observed between normal and neoplastic mucosas (P < 0.0001) and between adenomas or intestinal-type adenocarcinoma and diffuse-type adenocarcinoma (P < 0.001 and P < 0.01, respectively). Simultaneous measurement of topo II alpha and nuclear DNA content by two-parameter flow cytometry revealed that the Jurkat cell line established from acute lymphocytic leukemia cells expressed the enzyme in cells at other than S and G2/M phases of the cell cycle whereas topo-II alpha-positive cells were predominantly observed in S and G2/M phases of the cell cycle in the cells from normal lymph nodes. These findings suggest that dys-regulation or qualitative changes of topo II alpha expression are associated with malignancy. Topo II immunostaining can thus detect proliferating cells in routinely processed tissue sections and can indicate the altered topo II alpha expression in human cancers, which may be related to the sensitivity to topo-II-targeted chemotherapeutic agents.

Post-translational histone modifications play a critical role in genome functions such as epigenetic gene regulation and genome maintenance. The tail of the histone H4 N-terminus contains several amino acids that can be acetylated and methylated. Some of these modifications are known to undergo drastic changes during the cell cycle. In this study, we generated a panel of mouse monoclonal antibodies against histone H4 modifications, including acetylation at K5, K8, K12, and K16, and different levels of methylation at K20. Their specificity was evaluated by ELISA and immunoblotting using synthetic peptide and recombinant proteins that harbor specific modifications or amino acid substitutions. Immunofluorescence confirmed the characteristic distributions of target modifications. An H4K5 acetylation (H4K5ac)-specific antibody CMA405 reacted with K5ac only when the neighboring K8 was unacetylated. This unique feature allowed us to detect newly assembled H4, which is diacetylated at K5 and K12, and distinguish it from hyperacetylated H4, where K5 and K8 are both acetylated. Chromatin immunoprecipiation combined with deep sequencing (ChIP-seq) revealed that acetylation of both H4K8 and H4K16 were enriched around transcription start sites. These extensively characterized and highly specific antibodies will be useful for future epigenetics and epigenome studies.