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Major advances in the chromatin and epigenetics fields have uncovered the importance of core histones, histone variants and their post-translational modifications (PTMs) in modulating chromatin structure. However, an acutely understudied related feature of chromatin structure is the role of linker histone H1. Previous assumptions of the functional redundancy of the 11 nonallelic H1 variants are contrasted by their strong evolutionary conservation, variability in their potential PTMs, and increased reports of their disparate functions, sub-nuclear localizations and unique expression patterns in different cell types. The commonly accepted notion that histone H1 functions solely in chromatin compaction and transcription repression is now being challenged by work from multiple groups. These studies highlight histone H1 variants as underappreciated facets of chromatin dynamics that function independently in various chromatin-based processes. In this review, we present notable findings involving the individual somatic H1 variants of which there are seven, underscoring their particular contributions to distinctly significant chromatin-related processes.
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Cromatina/metabolismo , Variação Genética , Histonas/metabolismo , Animais , Sequência Conservada , Regulação da Expressão Gênica , Histonas/genética , Humanos , Relação Estrutura-AtividadeRESUMO
Reflective conversations between teachers and coaches are critical to helping teachers improve their classroom instruction. Coaches who encourage teachers to "see, think, and do" are better able to facilitate meaningful reflective conversations with teachers. The "See, Think, Do" framework consists of six steps (observe, describe, process, analyze, draw conclusions, and plan) that can be used to help coaches engage in reflective conversations with teachers. The framework can be readily implemented in remote and face-to-face coaching modalities and in one-on-one and small group delivery formats. Suggestions and strategies for implementing the framework in ongoing coach-teacher conversations are provided.
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OBJECTIVE: This study used matched samples from schools in the states of Victoria, Australia and Washington, United States (US), to compare sexual behaviour in early adolescence. It was hypothesised that the contrasting dominant policy objectives of harm minimisation in Australia and abstinence in the US would result in state differences for markers of sexual risk, mirroring prior cross-national findings in substance use. METHOD: A two-stage cluster sampling approach was used to recruit students from the two states. Self-reported sexual behaviour was examined for 1,596 students in annual surveys from Grade 7 in 2002 to Grade 9 in 2004. Prevalence estimates were derived for each measure of sexual behaviour, and comparisons were made between gender groups in each state. RESULTS: State differences were found for girls' first sex, with significantly more girls in Washington than Victoria having had sex by Grade 7. By Grade 9, significantly more girls in Victoria reported sex in the last year and more sexual partners than girls in Washington. A large proportion of Grade 9 students across both states reported inconsistent contraception use. CONCLUSIONS: Contradicting the abstinence policy objective, first sex by Grade 7 was more prevalent in Washington than Victoria. Whilst sexual behaviour was more prevalent in Grade 9 in Victoria, the sexually active showed no clear cross-national differences in markers of risk such as contraception use and pregnancy outcomes. Findings demonstrate few cross-national differences in adolescent sexual behaviour despite the different policy contexts of Victoria, Australia and Washington, US.
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The histone chaperone FACT is upregulated during mammary tumorigenesis and necessary for the viability and growth of breast tumor cells. We established that only proliferating tumor cells are sensitive to FACT knockdown, suggesting that FACT functions during DNA replication in tumor cells but not in normal cells. We hypothesized that the basal level of replication stress defines the FACT dependence of cells. Using genetic and chemical tools, we demonstrated that FACT is needed to overcome replication stress. In the absence of FACT during replication stress, the MCM2-7 helicase dissociates from chromatin, resulting in the absence of ssDNA accumulation, RPA binding, and activation of the ATR/CHK1 checkpoint response. Without this response, stalled replication forks are not stabilized, and new origin firing cannot be prevented, leading to the accumulation of DNA damage and cell death. Thus, we propose a novel role for FACT as a factor preventing helicase dissociation from chromatin during replication stress.
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Dano ao DNA , Replicação do DNA/genética , Proteínas de Ligação a DNA/genética , Proteínas de Grupo de Alta Mobilidade/genética , Chaperonas de Histonas/genética , Fatores de Elongação da Transcrição/genética , Animais , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Linhagem Celular , Células Cultivadas , Quinase 1 do Ponto de Checagem/metabolismo , Cromatina/genética , Cromatina/metabolismo , DNA de Cadeia Simples/genética , DNA de Cadeia Simples/metabolismo , Proteínas de Ligação a DNA/metabolismo , Proteínas de Grupo de Alta Mobilidade/metabolismo , Chaperonas de Histonas/metabolismo , Humanos , Células MCF-7 , Camundongos Knockout , Proteínas de Manutenção de Minicromossomo/genética , Proteínas de Manutenção de Minicromossomo/metabolismo , Interferência de RNA , Proteína de Replicação A/metabolismo , Fatores de Elongação da Transcrição/metabolismoRESUMO
Histone chaperone FACT is commonly expressed and essential for the viability of transformed but not normal cells, and its expression levels correlate with poor prognosis in patients with cancer. FACT binds several components of nucleosomes and has been viewed as a factor destabilizing nucleosomes to facilitate RNA polymerase passage. To connect FACT's role in transcription with the viability of tumor cells, we analyzed genome-wide FACT binding to chromatin in conjunction with transcription in mouse and human cells with different degrees of FACT dependence. Genomic distribution and density of FACT correlated with the intensity of transcription. However, FACT knockout or knockdown was unexpectedly accompanied by the elevation, rather than suppression, of transcription and with the destabilization of chromatin in transformed, but not normal cells. These data suggest that FACT stabilizes and reassembles nucleosomes disturbed by transcription. This function is vital for tumor cells because malignant transformation is accompanied by chromatin destabilization.
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PURPOSE: Limited longitudinal research has examined the adult health and behavioral outcomes associated with early adolescent sexual behavior. This paper examined whether adolescent sexual behavior predicted young adult health and social outcomes within longitudinal cohorts in Victoria, Australia. METHODS: Adolescents were recruited in 2002 to be state-representative of school students in Victoria, Australia, and resurveyed in 2003 and 2004. The sample responded to a web-based survey as young adults in 2010/2011. Multivariate negative binomial regression models examined the predictive effect of sex by age 15 on young adult outcomes (average age 21) of sexual risk taking, substance use, antisocial behavior, and psychological distress (Nâ¯=â¯2,147). RESULTS: After adjustment for other factors, sex at age 15 or younger (early sex) predicted higher rates of young adult sexual risk taking such as pregnancy, lifetime partners, and sex without using a condom. Early sex also predicted higher rates of young adult substance use (alcohol, tobacco, and/or illicit substance use) and antisocial behavior, but rates of adult psychological distress were not affected. CONCLUSIONS: This study found that early adolescent sex had unique predictive effects on a range of adverse young adulthood outcomes. Public health policies should synthesize longitudinal data on the risks of early sexual behavior, while advocating evidence-based adolescent sexual health promotion interventions.
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Comportamento do Adolescente/psicologia , Comportamento Sexual , Adolescente , Adulto , Alcoolismo/psicologia , Feminino , Humanos , Internet , Estudos Longitudinais , Masculino , Instituições Acadêmicas , Comportamento Sexual/psicologia , Comportamento Sexual/estatística & dados numéricos , Parceiros Sexuais/psicologia , Estudantes , Transtornos Relacionados ao Uso de Substâncias/psicologia , Inquéritos e Questionários , Sexo sem Proteção/estatística & dados numéricos , Vitória , Adulto JovemRESUMO
Understanding the underlying reasons for tumor aggressiveness, such as why some tumors grow slowly and locally, while others rapidly progress to a lethal metastatic disease, is still limited. This is especially critical in breast cancer (BrCa) due to its high prevalence and also due to the possibility that it can be detected early. Several oncogenes and tumor suppressors have been identified and are used in the prognosis and treatment of BrCa. However, even with these markers, the outcome within BrCa subtypes is highly variable. Chromatin organization has long been acknowledged as a factor that plays an important role in tumor progression, but molecular mechanisms defining chromatin dynamics are largely missing. We have recently found that histone chaperone FACT (facilitates chromatin transcription) is overexpressed in ~18-20% of BrCa cases. FACT is elevated upon transformation of mammary epithelial cells and is essential for viability of tumor cells. BrCa cells with high FACT have a more aggressive transcriptional program than those with low FACT cells. Based on this we propose that FACT may be a marker of aggressive BrCa. In this study, we aimed to comprehensively characterize the pattern of FACT expression in BrCa in relation to other molecular and clinical prognostic markers. We developed and tested an assay for the detection and quantitation of protein levels of both FACT subunits, SSRP1, and SPT16, in clinical samples. We compared the value of mRNA and protein as potential markers of disease aggressiveness using a large cohort of patients (n=1092). We demonstrated that only SSRP1 immunohistochemical staining is a reliable indicator of FACT levels in tumor samples. High SSRP1 correlated with known markers of poor prognosis, such as negative hormone receptor status, presence of Her2, high-grade tumors, and tumors of later clinical stage. At the same time, no strong correlation between SSRP1 expression and survival was detected when all samples were analyzed together. Clear trend toward longer survival of patients with low or no SSRP1 expression in tumor samples was seen in several subgroups of patients, and most importantly significant association of high SSRP1 expression with shorter disease-free survival was detected in patients with early-stage and low-grade BrCa, the category of patients with the highest demand in predictive marker of disease progression.
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Although breast cancer (BrCa) may be detected at an early stage, there is a shortage of markers that predict tumor aggressiveness and a lack of targeted therapies. Histone chaperone FACT, expressed in a limited number of normal cells, is overexpressed in different types of cancer, including BrCa. Recently, we found that FACT expression in BrCa correlates with markers of aggressive BrCa, which prompted us to explore the consequences of FACT inhibition in BrCa cells with varying levels of FACT.FACT inhibition using a small molecule or shRNA caused reduced growth and viability of all BrCa cells tested. Phenotypic changes were more severe in "high- FACT" cells (death or growth arrest) than in "low-FACT" cells (decreased proliferation). Though inhibition had no effect on the rate of general transcription, expression of individual genes was changed in a cell-specific manner. Initially distinct transcriptional profiles of BrCa cells became similar upon equalizing FACT expression. In "high-FACT" cells, FACT supports expression of genes involved in the regulation of cell cycle, DNA replication, maintenance of an undifferentiated cell state and regulated by the activity of several proto-oncogenes. In "low-FACT" cells, the presence of FACT reduces expression of genes encoding enzymes of steroid metabolism that are characteristic of differentiated mammary epithelia.Thus, we propose that FACT is both a marker and a target of aggressive BrCa cells, whose inhibition results in the death of BrCa or convertion of them to a less aggressive subtype.