The engagement of histone lysine methyltransferases with nucleosomes: structural basis, regulatory mechanisms, and therapeutic implications

Histone lysine methyltransferases (HKMTs) deposit methyl groups onto lysine residues on histones and play important roles in regulating chromatin structure and gene expression. The structures and functions of HKMTs have been extensively investigated in recent decades, significantly advancing our understanding of the dynamic regulation of histone methylation. Here, we review the recent progress in structural studies of representative HKMTs in complex with nucleosomes (H3K4, H3K27, H3K36, H3K79, and H4K20 methyltransferases), with emphasis on the molecular mechanisms of nucleosome recognition and trans-histone crosstalk by these HKMTs. These structural studies inform HKMTs' roles in tumorigenesis and provide the foundations for developing new therapeutic approaches targeting HKMTs in cancers.

Cut-off values of immunological tests to identify patients at high risk of severe lupus nephritis

Cut-off values for anti-dsDNA, anti-nucleosome and anti-C1q antibodies tests and for complement-mediated hemolytic activity (CH50) were explored to identify patients with high risk of developing severe lupus nephritis (LN). Forty-one patients with confirmed systemic lupus erythematosus (SLE) were identified; their levels for the three antibodies and complement had been measured on a same serum sample. These patients were classified based on the presence of renal involvem ent; sixteen had active proliferative LN. With the cut-off values accepted in the laboratory for SLE diagnosis (anti-dsDNA > 100 UI/ml, anti-nucleosome > 50 U/ ml or CH50 < 190 UCH50%) no significant differences were found between patients with and without LN. Anti-C1q > 40 U/ml showed a statistically significant association with LN and had 80% of specificity. Cut-off values for LN identified by Receiver Operating Characteristic curves (ROC) were higher for anti-dsDNA (> 455 IU/ml) and anti-nucleosome (>107 U/ml), lower for CH50 (< 150 UCH50%) and, for anti-C1q (> 41 U/ml) coincided with the cut-off values accepted for SLE. Anti-C1q > 134 U/ml had a 92% of specificity, 56% of sensibility and was associated with a fifteen-fold increased risk of LN. The simultaneous presence of anti-nucleosome > 107 U/ml and anti-C1q > 134 U/ml was associated with a 27-fold higher probability for LN. According to these results, the cut-off values used to detect SLE activity could be inadequate to identify patients at high risk of severe LN.

Se exploraron valores de corte para los ensayos de anti-ADNdc, anti-nucleosoma, anti-C1q y complemento hemolítico total (CH50) capaces de identificar los casos con mayor riesgo de nefritis lúpica (NL) grave. Se seleccionaron 41 pacientes ≥ 16 años con lupus eritematoso sistémico (LES) confirmado que tenían titulados los niveles de los tres anticuerpos y CH50, en una misma muestra de suero. Fueron clasificados según presencia de compromiso renal; 16 presentaron formas proliferativas de NL activa. Con los valores de corte aceptados por el laboratorio para el diagnóstico de LES (anti-ADNdc > 100 UI/ml, anti-nucleosoma > 50 U/ml o un CH50 < 190 UCH50%) no se encontraron diferencias significativas entre casos con y sin NL. Un anti-C1q > 40 U/ml tuvo una especificidad del 80% y mostró una asociación estadísticamente significativa con NL. Al aplicar curvas Receiver Operating Characteristic (ROC) para NL, se identificaron valores de corte más altos para anti-ADNdc (> 455 IU/ml) y anti-nucleosoma (> 107 U/ml), más bajo para CH50 (< 150 UCH50%) y para el anti-C1q (> 41 U/ml) coincidió con el aceptado para diagnóstico de LES. Un anti-C1q > 134 U/ml presentó una sensibilidad del 56%, una especificidad del 92% y se asoció con quince veces más riesgo de NL. La presencia simultánea de anti-C1q > 134 U/ml y anti-nucleosoma > 107 U/ml se asoció 27 veces más riesgo de NL. De acuerdo a estos resultados los valores de corte empleados para actividad en pacientes con LES podrían resultar inadecuados para identificar pacientes con mayor riesgo de NL grave.

Epigenetics: A key paradigm in reproductive health / 대한생식의학회지

It is well established that there is a heritable element of susceptibility to chronic human ailments, yet there is compelling evidence that some components of such heritability are transmitted through non-genetic factors. Due to the complexity of reproductive processes, identifying the inheritance patterns of these factors is not easy. But little doubt exists that besides the genomic backbone, a range of epigenetic cues affect our genetic programme. The inter-generational transmission of epigenetic marks is believed to operate via four principal means that dramatically differ in their information content: DNA methylation, histone modifications, microRNAs and nucleosome positioning. These epigenetic signatures influence the cellular machinery through positive and negative feedback mechanisms either alone or interactively. Understanding how these mechanisms work to activate or deactivate parts of our genetic programme not only on a day-to-day basis but also over generations is an important area of reproductive health research.

Are 30 minutes of rest between two incremental shuttle walking tests enough for cardiovascular variables and perceived exertion to return to baseline values?

Objective: To verify whether 30 minutes of rest between two incremental shuttle walking tests (ISWT) are enough for cardiovascular variables and perceived exertion to return to baseline values in healthy subjects in a broad age range. Method: The maximal exercise capacity of 334 apparently healthy subjects (age ≥18) was evaluated using the ISWT. The test was performed twice with 30 minutes of rest in between. Heart rate (HR), arterial blood pressure (ABP), dyspnea, and leg fatigue were evaluated before and after each test. Subjects were allocated to 6 groups according to their age: G1: 18-29 years; G2: 30-39 years; G3: 40-49 years; G4: 50-59 years; G5: 60-69 years and G6: ≥70 years. Results: All groups had a good performance in the ISWT (median >90% of the predicted distance). The initial HR (HRi) of the second ISWT was higher than the first ISWT in the total sample (p<0.0001), as well as in all groups (p<0.0001). No difference was observed in the behavior of ABP (systolic and diastolic) and dyspnea between the two tests, but this difference occurred for leg fatigue (greater before the second ISWT) in G1 (p<0.05). Most subjects (58%) performed better in the second test. Conclusion: 30 minutes of rest between two ISWTs are not enough for all cardiovascular variables and perceived exertion to return to baseline values. However, this period appears to be sufficient for blood pressure and performance to recover in most subjects. .

Leishmania, Babesia and Ehrlichia in urban pet dogs: co-infection or cross-reaction in serological methods?

INTRODUCTION: The present study was designed to assess the occurrence of co-infection or cross-reaction in the serological techniques used for detecting the anti-Leishmania spp., -Babesia canis vogeli and -Ehrlichia canis antibodies in urban dogs from an area endemic to these parasites. METHODS: The serum samples from dogs were tested for the Babesia canis vogeli strain Belo Horizonte antigen and Ehrlichia canis strain São Paulo by immunofluorescence antibody test (IFAT) and by anti-Leishmania immunoglobulin G (IgG) antibody detection to assess Leishmania infection. We used the following four commercial kits for canine visceral leishmaniasis: ELISA, IFAT, Dual Path Platform (DPP) (Bio Manguinhos(r)/FIOCRUZ/MS) and a rK39 RDT (Kalazar Detect Canine Rapid Test; Inbios). RESULTS : Of 96 serum samples submitted to serological assays, 4 (4.2%) were positive for Leishmania as determined by ELISA; 12 (12.5%), by IFAT; 14 (14.6%) by rK39 RDT; and 20 (20.8%), by DPP. Antibodies against Ehrlichia and Babesia were detected in 23/96 (23.9%) and 30/96 (31.2%) samples, respectively. No significant association was identified between the results of tests for detecting Babesia or Ehrlichia and those for detecting Leishmania (p-value>0.05). CONCLUSIONS: In the present study, we demonstrated co-infection with Ehrlichia or Babesia and Leishmania in dogs from Minas Gerais (Brazil); we also found that the serological tests that were used did not cross-react. .

Total triterpenoids from Ganoderma Lucidum suppresses prostate cancer cell growth by inducing growth arrest and apoptosis / 华中科技大学学报（医学）（英德文版）

In this study, one immortalized human normal prostatic epithelial cell line (BPH) and four human prostate cancer cell lines (LNCaP, 22Rv1, PC-3, and DU-145) were treated with Ganoderma Lucidum triterpenoids (GLT) at different doses and for different time periods. Cell viability, apoptosis, and cell cycle were analyzed using flow cytometry and chemical assays. Gene expression and binding to DNA were assessed using real-time PCR and Western blotting. It was found that GLT dose-dependently inhibited prostate cancer cell growth through induction of apoptosis and cell cycle arrest at G1 phase. GLT-induced apoptosis was due to activation of Caspases-9 and -3 and turning on the downstream apoptotic events. GLT-induced cell cycle arrest (mainly G1 arrest) was due to up-regulation of p21 expression at the early time and down-regulation of cyclin-dependent kinase 4 (CDK4) and E2F1 expression at the late time. These findings demonstrate that GLT suppresses prostate cancer cell growth by inducing growth arrest and apoptosis, which might suggest that GLT or Ganoderma Lucidum could be used as a potential therapeutic drug for prostate cancer.

Anticuerpos antinucleosoma frente a marcadores inmunológicos convencionales en el diagnóstico de la actividad del lupus eritematoso sistémico / Anti-nucleosome antibodies against conventional Immunological markers in the diagnosis of SLE activity

OBJETIVOS: examinar el perfil de anticuerpos en pacientes con lupus eritematoso sistémico y establecer la correlación entre los niveles de anticuerpos y la actividad de la enfermedad y de la nefritis lúpica. MÉTODOS: en 213 pacientes con lupus eritematoso sistémico, atendidos de forma consecutiva, se determinaron los anticuerpos anti-DNA de doble cadena (DNAdc), antinucleosoma (Nu), anti-Sm, anti-RNP, anti-Ro, anti-La y anti-Scl-70 por ensayo inmunoadsorbente ligado a enzima (ELISA), el C3 y el C4. La actividad de la enfermedad fue evaluada por el índice SLEDAI-2K, sin la contribución de anti-DNAdc, C3 ni C4. Los niveles de anticuerpos, el complemento y la actividad del lupus eritematoso sistémico fueron correlacionados. RESULTADOS: los niveles de todos los anticuerpos resultaron superiores significativamente en los pacientes en fase activa de la enfermedad con respecto a los que se hallaban en la fase inactiva. Los coeficientes de correlación de Spearman más altos con la puntuación de SLEDAI-2K correspondieron a los anti-Nu y anti-DNAdc (p= 0,856 y p= 0,616, respectivamente, p < 0,001 para ambos). Las áreas bajo de la curva (AUC) del análisis COR de la actividad del LES fueron en orden decreciente para los anti-Nu= 0,948, anti-DNAdc= 0,810, anti-RNP= 0,705, C4= 0,704, anti-Sm= 0,703, C3= 0,688, anti-Scl-70= 0,611, anti-La= 0,601 y anti-Ro= 0,593; y de la actividad renal para los anti-Nu= 0,845, anti-DNAdc= 0,755, C4= 0,694, C3= 0,670, anti-Sm= 0,641, anti-RNP= 0,630, anti-Scl-70= 0,611, anti-Ro= 0,593 y anti-La= 0,567. CONCLUSIÓN: los anticuerpos anti-Nu mostraron una capacidad discriminatoria excelente para la actividad del LES y de la actividad renal lúpica, superior a la de los anti-DNAdc y el resto de los marcadores.

OBJECTIVES: to examine the profile of antibodies in patients with systemic lupus erythematosus and establish the correlation between antibody levels and disease activity, and lupus nephritis. METHODS: anti-double stranded DNA (dsDNA), antinucleosoma (Nu), anti-Sm, anti-RNP, anti-Ro, anti-La, and anti-Scl-70 antibodies by enzyme-linked immunosorbent assay (ELISA) as well as C3 and C4 were determined in 213 patients with systemic lupus erythematosus who were treated consecutively. Disease activity was assessed by the SLEDAI 2K-index, without the contribution of anti-dsDNA, C3 or C4. The levels of antibodies, complement and activity of systemic lupus erythematosus were correlated. RESULTS: the levels of antibodies turned out to be remarkably higher in patients in the active phase of the disease compared to those who were in the inactive phase. The higher Spearman correlation coefficients with SLEDAI-2K score corresponded to the anti-Nu and anti-dsDNA (p = 0.856 and p = 0.616, respectively, p <0.001 for both). The areas under the ROC curve analysis of the activity of systemic lupus erythematosus were in descending order as follows: anti-Nu = 0.948; anti-dsDNA = 0.810; anti-RNP = 0.705; C4 = 0.704; anti-Sm = 0.703; C3 = 0.688; anti-Scl-70 = 0.611; = 0.601 anti-La. Anti-Ro = 0.593; and renal activity for anti-Nu = 0.845; anti-dsDNA = 0.755; C4= 0.694; C3 = 0.670; anti-Sm = 0.641; anti-RNP = 0.630; anti-Scl-70 = 0.611; anti-Ro = 0.593 and anti-La = 0.567. CONCLUSION: the anti-Un exhibit excellent activity discriminating capacity of SLE lupus and renal activity, higher than the anti-dsDNA and other markers.

El papel de los anticuerpos anti-cromatina, antiC1qy las fracciones del complemento unidas a célulasen el diagnóstico precoz de actividad lúpica / Role of Anti-chromatin, anti-C1q and cell bound complement activation products in the early diagnosis of Systemic Lupus Erythematosus disease activity

Actualmente se percibe una necesidad apremiante en la identificación y validación debiomarcadores que reflejen tempranamente el inicio de actividad lúpica o que se conviertanen predictores de la misma. La actividad clínica del lupus eritematoso sistémico (LES) esondulante a lo largo del tiempo y la actividad subyacente persistente lleva a daño tisular.Este daño es reflejo de cambios irreversibles en la función y estructura orgánica, por loque la prevención, más que el tratamiento, debería ser la meta de cualquier terapia enLES y así lograr disminuir la morbimortalidad y los costos directos e indirectos causadospor la enfermedad. Es necesario encontrar biomarcadores no invasivos de actividadlúpica que no solo permitan tomar de forma oportuna decisiones terapéuticas, sino quetambién se correlacionen con los desenlaces clínicos y sean útiles en los ensayos clínicos,permitiendo acortar el tiempo del desarrollo de estos estudios. Este artículo pretendebuscar la evidencia que se tiene con respecto a los nuevos biomarcadores existentes paraactividad de la enfermedad en LES y su utilidad actual y futura, enfatizando en la necesidadde buscar nuevas moléculas que permitan un diagnóstico más precoz de la actividad de laenfermedad.

There is a need for the identification and validation of biomarkers that reflect the early onset of lupus activity or may be predictors of this. The clinical activity of systemic lupus erythematosus (SLE) fluctuates over time and the underlying activity leads to persistent tissue damage. This damage is a reflection of irreversible changes in the function and organic structure, so prevention, rather than treatment, should be the goal of any therapy in SLE.This will reduce morbidity, mortality, direct and indirect costs caused by the disease. It is necessary to find biomarkers of lupus activity that not only allow making treatment decisions in the short term, but also to correlate with clinical outcomes. These could also be useful in clinical trials and may shorten the duration of these studies. This article aims to find evidence on new biomarkers for SLE disease activity, and their current and future use. Emphasis will be made on the need to find new molecules for an early diagnosis of disease activity.

Influencia de las modificaciones epigenéticasocasionadas por el consumo de cigarrillos en relación con la disminución del hueso alveolar-revisión de la literatura / Epigenetic influence of changes caused by cigarette consumption in relation to the bone reduction alveolar-literature review

La epigenética hoy en día constituye uno de los temas de mayor interés en el campo científico, debido a la relación que se ha encontrado con cambios fenotípicos, siendo la metilación del ADN y la desacetilación de las histonas los principales eventos que la caracterizan. A su vez, se ha evidenciado en una amplia gama de patologías. Es por esto, que los factores que inducen estos cambios epigenéticos pueden ser ambientales (como el cigarrillo) o hereditarios. Hay que destacar que entre las alteraciones en las que se ha visto involucrada a la epigenética se encuentra disminución en la cantidad y calidad del hueso en el complejo maxilar-mandíbula, los cuales, a su vez son considerados parámetros de vital importancia en tratamientos odontológicos rehabilitadores. El objetivo de la presente investigación realizar una revisión a la literatura actualizada con el propósito de describir la influencia de las modificaciones epigenéticas ocasionadas por el consumo de cigarrillos y su asociación con la resorción ósea alveolar.

In the present time, the epigenetics is one of the topics with most interest on the scientific field, due to the relationship that has been found with phenotypic changes, been epigenetic´s main event the DNA methylation and the Histone acetylation, that at the same time have been evidenced on a great quantity of pathologies. Because of this, the epigenetics changes are induced by environmental (like smoking) and hereditary factors. Is worth to mention, that among the alterations on which the epigenetic has been related is found the decrease en the quality and quantity of the bone on the maxillary-mandibular complex, which are also consider important parameters for successful dental rehabilitators treatments. A current bibliographic revision was made with the purpose of describe the influence of epigenetic´s modifications involved on the smoking in relationships with the of the alveolar bone loss.

Analysis of Gene Expression in Cyclooxygenase-2-Overexpressed Human Osteosarcoma Cell Lines

Osteosarcoma is the most common primary bone tumor, generally affecting young people. While the etiology of osteosarcoma has been largely unknown, recent studies have suggested that cyclooxygenase-2 (COX-2) plays a critical role in the proliferation, migration, and invasion of osteosarcoma cells. To understand the mechanism of action of COX-2 in the pathogenesis of osteosarcoma, we compared gene expression patterns between three stable COX-2-overexpressing cell lines and three control cell lines derived from U2OS human osteosarcoma cells. The data showed that 56 genes were upregulated, whereas 20 genes were downregulated, in COX-2-overexpressed cell lines, with an average fold-change > 1.5. Among the upregulated genes, COL1A1, COL5A2, FBN1, HOXD10, RUNX2, and TRAPPC2are involved in bone and skeletal system development, while DDR2, RAC2, RUNX2, and TSPAN31are involved in the positive regulation of cell proliferation. Among the downregulated genes, HIST1H1D, HIST1H2AI, HIST1H3H, and HIST1H4C are involved in nucleosome assembly and DNA packaging. These results may provide useful information to elucidate the molecular mechanism of the COX-2-mediated malignant phenotype in osteosarcoma.

ENCODE: A Sourcebook of Epigenomes and Chromatin Language

Until recently, since the Human Genome Project, the general view has been that the majority of the human genome is composed of junk DNA and has little or no selective advantage to the organism. Now we know that this conclusion is an oversimplification. In April 2003, the National Human Genome Research Institute (NHGRI) launched an international research consortium called Encyclopedia of DNA Elements (ENCODE) to uncover non-coding functional elements in the human genome. The result of this project has identified a set of new DNA regulatory elements, based on novel relationships among chromatin accessibility, histone modifications, nucleosome positioning, DNA methylation, transcription, and the occupancy of sequence-specific factors. The project gives us new insights into the organization and regulation of the human genome and epigenome. Here, we sought to summarize particular aspects of the ENCODE project and highlight the features and data that have recently been released. At the end of this review, we have summarized a case study we conducted using the ENCODE epigenome data.

Epigenetic Modification in Systemic Rheumatic Diseases

Epigenetics is defined as an inheritable effect that influences gene activity, but does not involve a change in DNA sequence. Epigenetic gene regulation has an essential role in determining individual gene function and activity in each specific cell type. Epigenetics includes four predominant mechanisms: DNA methylation, histone modification, nucleosome positioning and microRNA (miRNA). These mechanisms influence gene expression, cell differentiation, proliferation, DNA repair and replication. Epigenetic modifications are far more sensitive to environmental stimuli than DNA sequence alterations. Candidate gene approaches have identified a small set of genes that undergo epigenetic changes, such as aberrant DNA demethylation, histone modification, as well as regulation by miRNA in rheumatic diseases. It is well known that T cells from patients with SLE or RA, as well as synovial fibroblasts from individuals with RA, have sequences undergoing DNA hypomethylation and/or histone modifications. In addition, miRNA regulates the gene expression by pairing with its target mRNAs and is often deregulated in systemic rheumatic diseases. High-throughput approaches are necessary for screening the epigenetic alterations, and it is essential to screen the specific tissue and cell types that are relevant to the disease pathogenesis. Identification of cell-specific targets of the epigenetic deregulation in rheumatic disorders will provide clinical markers for the diagnosis, disease progression and response to therapy. Our understanding of epigenetics is in its infancy. New generation of pharmaceuticals, which manipulate the epigenome to the switch targeted genes on or off are under investigation. The new field of repairing or optimizing the epigenome through epigenetic modifier and/or diet is wide open.

Anticorpos antinucleossomo e síndrome antifosfolipídica: estudo observacional / Antinucleosome antibodies and primary antiphospholipid syndrome: an observational study

OBJETIVO: Avaliar a associação entre a presença de anticorpos antinucleossomo (anti-NCS) e a síndrome antifosfolipídica primária (SAFP) e o posterior desenvolvimento de lúpus eritematoso sistêmico (LES). MATERIAIS E MÉTODOS: Trinta e seis mulheres com o diagnóstico de SAFP foram avaliadas prospectivamente para manifestações de doenças reumáticas autoimunes e para a presença de anticorpos antifosfolípides, anticorpos antinucleares e anti-NCS/cromatina. RESULTADOS: Após um período médio de seguimento de 45,7 meses, anticorpos anti-NCS/cromatina foram detectados em apenas uma paciente (2,8%), que desenvolveu manifestações de LES tais como poliartrite, linfopenia, neurite óptica, lesões compatíveis com esclerose múltipla em substância branca cerebral e perfil de autoanticorpos altamente sugestivo de LES. CONCLUSÃO: A frequência de anticorpos anti-NCS/cromatina é baixa em pacientes com SAFP, e sua presença pode associar-se ao desenvolvimento de manifestações de LES.

OBJECTIVE: To study the association of anti-nucleosome (anti-NCS) antibodies in primary antiphospholipid syndrome (APS) and the development of systemic lupus erythematosus (SLE) during follow-up. MATERIALS AND METHODS: Thirty-six women with primary APS were evaluated prospectively for clinical features of systemic autoimmune diseases and for the presence of antiphospholipid antibodies, antinuclear antibodies and anti-NCS/chromatin antibodies. RESULTS: After a mean follow-up period of 45.7 months, anti-NCS/chromatin antibodies were detected in only one patient (2.8%), who developed features of SLE including polyarthritis, lymphopenia, optic neuritis, multiple sclerosis-like lesions, and an autoantibody profile suggestive of SLE. CONCLUSION: The frequency of anti-NCS/chromatin antibodies in primary APS patients is very low, and they may be associated with the development of SLE manifestations.

Expression of HMGB1 and HMGN2 in gingival tissues, GCF and PICF of periodontitis patients and peri-implantitis

High mobility group chromosomal protein B1 (HMGB1) and N2 (HMGN2), two members of High mobility group (HMG) family, play important role in inflammation. The purposes of this study were to investigate the expression of HMGB1 and HMGN2 in periodontistis. The expression of HMGB1 and HMGN2 mRNA in gingival tissues and gingival crevicular fluid (GCF) in chronic periodontitis (CP), generalized aggressive periodontitis (G-AgP) patients and healthy subjects was detected by real-time PCR. The protein level of HMGB1 and HMGN2 in peri-implant crevicular fluid (PICF), peri-implant crevicular fluid of peri-implantitis (PI-PICF) and normal patients was determined by Western blotting. Furthermore, IL-1â, IL-6, IL-8, TNF-á and HMGB1 levels in GCF, PI-PICF and healthy-PICF samples from different groups were determined by ELISA. HMGN2 expression was increased in inflamed gingival tissues and GCF from CP and G-ApG groups compared to control group. HMGB1 expression was the highest in the gingival tissues and GCF from CP patients and was accompanied by increased concentrations of IL-1â, IL-6, IL-8 proinflammaory cytokines. To our knowledge, this is the first study reporting that the expression of HMGB1 and HMGN2 was increased in the gingival tissues and GCF in CP and G-AgP and the PICF in PICF. Our data suggest that HMGB1 may be a potential target for the therapy of periodontitis and PI.

Nucleosome assembly and epigenetic inheritance

In eukaryotic cells, histones are packaged into octameric core particles with DNA wrapping around to form nucleosomes, which are the basic units of chromatin (Kornberg and Thomas, 1974). Multicellular organisms utilise chromatin marks to translate one single genome into hundreds of epigenomes for their corresponding cell types. Inheritance of epigenetic status is critical for the maintenance of gene expression profile during mitotic cell divisions (Allis et al., 2006). During S phase, canonical histones are deposited onto DNA in a replication-coupled manner (Allis et al., 2006). To understand how dividing cells overcome the dilution of epigenetic marks after chromatin duplication, DNA replication coupled (RC) nucleosome assembly has been of great interest. In this review, we focus on the potential influence of RC nucleosome assembly processes on the maintenance of epigenetic status.

Histones, histone chaperones and nucleosome assembly

Chromatin structure governs a number of cellular processes including DNA replication, transcription, and DNA repair. During DNA replication, chromatin structure including the basic repeating unit of chromatin, the nucleosome, is temporarily disrupted, and then reformed immediately after the passage of the replication fork. This coordinated process of nucleosome assembly during DNA replication is termed replication-coupled nucleosome assembly. Disruption of this process can lead to genome instability, a hallmark of cancer cells. Therefore, addressing how replication-coupled nucleosome assembly is regulated has been of great interest. Here, we review the current status of this growing field of interest, highlighting recent advances in understanding the regulation of this important process by the dynamic interplay of histone chaperones and histone modifications.

Apoptosis in pulp elimination during physiological root resorption in human primary teeth

Pulp samples of 50 healthy human teeth with indication for extraction were examined to evaluate the role of apoptosis in pulp elimination during physiological root resorption. Two groups were formed: a test group (n=30) composed of pulp samples of primary teeth with physiological root resorption and a control group (n=20) composed of pulp samples of permanent maxillary third molars. Morphological evidence of apoptosis as well as in situ detection of cellular DNA fragmentation by TUNEL assay and detection of internucleosomal pattern of fragmentation of the genomic DNA by electrophoresis were observed. The apoptotic index of the primary tooth group was significantly higher than that of the permanent tooth group (51.01 ± 0.52 versus 25.32 ± 0.68) (p<0.001). TUNEL reaction showed intense and diffuse labeling in the pulp samples of primary teeth, which were discrete in the controls. Intense DNA internucleosomal fragmentation, a specific pattern for apoptosis, was observed in primary tooth pulps DNA by electrophoresis, in the permanent tooth pulps this pattern fragmentation of the genomic DNA for apoptosis were not present. These results seem to indicate a role of apoptosis in pulp elimination during the physiological root resorption of human primary teeth.

Cinqüenta amostras de polpas de dentes humanos hígidos com indicação para extração foram estudadas a fim de verificar a participação da apoptose na eliminação pulpar durante a reabsorção radicular fisiológica. As amostras foram divididas em 2 grupos: um grupo de estudo composto por 30 polpas de dentes decíduos hígidos com reabsorção radicular fisiológica, e um grupo controle composto por 20 polpas de terceiros molares superiores hígidos. Evidências morfológicas de apoptose, bem como detecção in situ da fragmentação do DNA genômico via reação de TUNEL e também a detecção do padrão internucleossômico de fragmentação do DNA genômico via eletroforese foram observados. O índice apoptótico foi maior no grupo de dentes decíduos (51,01 ± 0,52) quando comparado ao grupo de dentes permanentes (25,32 ± 0,68) (p<0,001). Quanto à reação de TUNEL, houve intensa marcação positiva para fragmentação do genoma no grupo de estudo, o que ocorreu de maneira discreta nos controle. A eletroforese do DNA genômico mostrou fragmentação internucleossômica, em um padrão específico de apoptose nas amostras de dentes decíduos o que não ocorreu no grupo de dentes permanentes. Estes achados parecem indicar a apoptose como um mecanismo importante na eliminação do tecido pulpar durante a reabsorção radicular fisiológica de dentes decíduos humanos.

Comparison between Therapeutic Efficacies of Histone Deacetylase Inhibitors and Established Drug Regimens Against Breast Cancer Cells using the Histoculture Drug Response Assay / 한국유방암학회지

PURPOSE: Histone deacetylase inhibitors (HDACIs) induce accumulation of acetylated histones in nucleosomes, which lead to reactivate gene expression and inhibit the growth and survival of tumor cells. This study evaluated the efficacy of HDACIs in breast cancer cells in comparison with other established drug regimens. METHODS: Drug responses of tumor samples from mastectomy specimens of 78 breast cancer patients were evaluated using the histoculture drug response assay (HDRA). Tumor inhibition rates (IRs) of established drug regimens such as doxorubicin, cyclophosphamide, doxorubicin with cyclophosphamide (AC), paclitaxel, docetaxel and doxorubicin with docetaxel (AT), as well as those of three HDACIs (SAHA, PXD101, and a novel compound CG-2) were evaluate. RESULTS: The percentages of chemosensitive tumors (chemoresponsiveness) were 26.9-60.3% with established regimens and 61.5-73.1% with HDACIs when the cutoff value for inhibition rate was set at 30%. Breast cancer cells appeared to be more chemoresponsive to HDACIs than to established drug regimens. Chemoresponsiveness to AT was the highest among the established drug regimens. A combination regimen offered higher activity than did a single drug (doxorubicin vs AT; p<0.001). HER2/Neu-overexpressing breast cancers were chemosensitive to SAHA and AT (p=0.031 and 0.04, respectively). CONCLUSION: Our findings show that breast cancer cells were sensitive to HDACIs, with therapeutic efficacies comparable to those of established drug regimens. Specific biological markers such as HER2/Neu could be assessed for effectiveness as HDACIs chemosensitivity markers in further clinical trials.