The replacement histone H2A.Z in a hyperacetylated form is a feature of active genes in the chicken

The replacement histone H2A.Z is variously reported as being linked to gene expression and preventing the spread of heterochromatin in yeast, or concentrated at heterochromatin in mammals. To resolve this apparent dichotomy, affinity-purified antibodies against the N-terminal region of H2A.Z, in both a triacetylatedandnon- acetylatedstate, areusedin native chromatin immmuno-precipitation experiments with mononucleosomes from three chicken cell types. The hyperacetylated species concentrates at the 50 end of active genes, both tissue specific and housekeeping but is absent from inactive genes, while the unacetylated form is absent from both active and inactive genes. A concentration of H2A.Z is also found at insulators under circumstances implying a link to barrier activity but not to enhancer blocking. Although acetylated H2A.Z is widespread throughout the interphase genome, at mitosis its acetylation is erased, the unmodified form remaining. Thus, although H2A.Z may operate as an epigenetic marker for active genes, its N-terminal acetylation does not

Characterisation of dosimetry in electron radiotherapy under different bolus applications

Radiation therapy with electron beams is a technique that continues to be used by many clinics. The characteristic depth dose with a dose build up and rapid dose drop off beyond the peak dose permits a lesion to be treated with a relatively uniform dose whilst sparing deeper normal tissue. There are three general methods employed to modulate electron beams; a)Intensity Modulated Electron Therapy b) Segmented-field Electron Conformal Therapy, c) Bolus Electron Conformal Therapy, which can be used to achieve one or a combination of three aims; 1) level an irregular surface and improve dose distributions (missing tissue compensator), 2) reduce the penetration of the electron beam in certain areas (shaping isodoses closer to the distal edge of the target volume), 3) increase the surface dose at energies below 10MeV. The most commonly employed method in a general radiotherapy practice to modify an electron beam is the application of a tissue like material (bolus) to the skin surface, in the strictest sense this is not Bolus Electron Conformal Therapy (BolusECT) but rather an element of the method as the bolus applied usually lacks sophisticated contouring. The first two methods mentioned are both technically and resource challenging for a general radiotherapy clinic. Unfortunately the application of bolus does have some limitations; it is not usually sterile and the daily application in areas where there may be ulcerated, necrotic or haemorrhaging tissue can lead to an unhygienic situation. In addition there are times when it is difficult to mould or reproducibly position the bolus to the particular surface irregularities leading to suboptimal treatment delivery. Moving the bolus to the applicator level alleviates the contact and positional reproducibility difficulties however it does introduce new challenges in understanding how this will affect the electron beam dosimetry for the clinical treatment. This thesis provides the reader with some of the information necessary to understand the new challenges

The replacement histone H2A.Z in a hyperacetylated form is a feature of active genes in the chicken

The replacement histone H2A.Z is variously reported as being linked to gene expression and preventing the spread of heterochromatin in yeast, or concentrated at heterochromatin in mammals. To resolve this apparent dichotomy, affinity-purified antibodies against the N-terminal region of H2A.Z, in both a triacetylatedandnon- acetylatedstate, areusedin native chromatin immmuno-precipitation experiments with mononucleosomes from three chicken cell types. The hyperacetylated species concentrates at the 50 end of active genes, both tissue specific and housekeeping but is absent from inactive genes, while the unacetylated form is absent from both active and inactive genes. A concentration of H2A.Z is also found at insulators under circumstances implying a link to barrier activity but not to enhancer blocking. Although acetylated H2A.Z is widespread throughout the interphase genome, at mitosis its acetylation is erased, the unmodified form remaining. Thus, although H2A.Z may operate as an epigenetic marker for active genes, its N-terminal acetylation does not

Evaluation of planned dosimetry when beam energies are substituted for a fraction of the treatment course

Purpose: The purpose of this technical study was to evaluate how the effect of changing beam energies for one to multiple fractions of a patient’s plan affected the overall dose delivered to the planning target volume (PTV) and surrounding organs at risk (OAR’s). Method: In this study, twenty-eight patient plans from treatment sites including the oesophagus, prostate, lung, spine, rectum, bladder, chest, scapula, and breast were evaluated in the Philips Pinnacle treatment planning system (TPS), of these 14 were originally planned with 15MV and 14 with 10MV. Each of these plans were substituted with a single to multiple fractions with 10MV and 15MV respectively while keeping the original monitor units the same.Results: It was determined that when the number of fractions of the substituted beam energy remained at one fifth or less of the overall fractions a change of dose of less than 2% to the PTV could be maintained. The OAR’s dose, when the plan had 20% of its fractions substituted with a different energy, were found to change by on average up to 3.5% and 2.3% for original plan energies of 15MV and 10MV respectively. The dose change calculated in the TPS was then verified using ion chamber measurements for bladder and oesophagus treatment plans. Conclusion: Results appear to indicate that the site of treatment was not an important factor when changing energy but the overall number of fractions versus the number of fractions substituted with an alternative energy was fundamental. These results may be clinically useful when a radiotherapy department have machines with different photon energies. In the event of a break down, when a patient needs to be urgently treated, it may be possible to treat them on another machine with a different energy, without an immediate recalculation in the TPS. This decision would depend upon the percentage of fractions of their overall treatment needing to be treated before the machine was repaired-------------------------------Cite this article as:Hawke S, Torrance A, Tremethick L. Evaluation of planned dosimetry when beam energies are substituted for a fraction of the treatment course. Int J Cancer Ther Oncol 2013; 1(2):01014.DOI: http://dx.doi.org/10.14319/ijcto.0102.

Short Histone H2A Variants: Small in Stature but not in Function

The dynamic packaging of DNA into chromatin regulates all aspects of genome function by altering the accessibility of DNA and by providing docking pads to proteins that copy, repair and express the genome. Different epigenetic-based mechanisms have been described that alter the way DNA is organised into chromatin, but one fundamental mechanism alters the biochemical composition of a nucleosome by substituting one or more of the core histones with their variant forms. Of the core histones, the largest number of histone variants belong to the H2A class. The most divergent class is the designated “short H2A variants” (H2A.B, H2A.L, H2A.P and H2A.Q), so termed because they lack a H2A C-terminal tail. These histone variants appeared late in evolution in eutherian mammals and are lineage-specific, being expressed in the testis (and, in the case of H2A.B, also in the brain). To date, most information about the function of these peculiar histone variants has come from studies on the H2A.B and H2A.L family in mice. In this review, we describe their unique protein characteristics, their impact on chromatin structure, and their known functions plus other possible, even non-chromatin, roles in an attempt to understand why these peculiar histone variants evolved in the first placeThis research was funded by the Australian National and Health Medical Research Council, grant application number 11423

Laser welding of fusion relevant steels for the European DEMO

The construction and maintenance of the European DEMO will require reliable joining of thick-walled Eurofer97 steel cooling pipes between in-vessel components in the reactor. To this end, laser welding has been investigated as a potential method for pipe joining. Two different techniques (keyhole laser welding and hybrid laser-laser welding) were used to produce test welds in Eurofer97 and P91 steel samples. Welds were also produced using different filler wires to reduce the hardness in the weldment region and improve the weld profile. Optical microscopy and hardness mapping were used to assess the quality of the welds produced. From the weld trials, suitable process parameters were identified that resulted in fully penetrated welds with good profiles. Here, we will present the results of the laser welding development process and the properties of the welds produced using these two techniques

Effects of HMGB-1 Overexpression on Cell-Cycle Progression in MCF-7 Cells

High mobility group-1 (HMGB-1) enhances the DNA interactions and possesses a transcriptional activation potential for several families of sequence-specific transcriptional activators. In order to examine the effect of HMGB-1 on the cell cycle progression in MCF-7 cells, the HMGB-1 expression vector was transfected into synchronized MCF-7 cells, and the effect of HMGB-1 overexpression on the cell cycle was examined. The HMGB-1 protein level in the transfected cells increased 4.87-fold compared to the non-transfected cells. There were few changes in the cell cycle phase distribution after HMGB-1 overexpression in the MCF-7 cells. Following the estrogen treatment, the cell cycle progressed in both the HMGB-1 overexpressed MCF-7 and the mock-treated cells. However, a larger proportion of HMGB-1 overexpressing MCF-7 cells progressed to the either S or G2 phase than the mock-treated cells. The mRNA levels of the cell cycle regulators changed after being treated with estrogen in both the HMGB-1 overexpressing MCF-7 and the mock-treated cells, but the changes in the expression level of the cell cycle regulator genes were more prominent in the HMGB-1 overexpressing MCF-7 cells than in the mock-treated cells. In conclusion, HMGB-1 overexpression itself does not alter the MCF-7 cell cycle progression, but the addition of estrogen to the HMGB-1 overexpressing MCF-7 cells appears to accelerate the cell cycle progression

Quantitative analysis of chromatin compaction in living cells using FLIM-FRET

FRET analysis of cell lines expressing fluorescently tagged histones on separate nucleosomes demonstrates that variations in chromosome compaction occur during mitosis

Acetylation of H2A.Z is a key epigenetic modification associated with gene deregulation and epigenetic remodeling in cancer

Histone H2A.Z (H2A.Z) is an evolutionarily conserved H2A variant implicated in the regulation of gene expression; however, its role in transcriptional deregulation in cancer remains poorly understood. Using genome-wide studies, we investigated the role of promoter-associated H2A.Z and acetylated H2A.Z (acH2A.Z) in gene deregulation and its relationship with DNA methylation and H3K27me3 in prostate cancer. Our results reconcile the conflicting reports of positive and negative roles for histone H2A.Z and gene expression states. We find that H2A.Z is enriched in a bimodal distribution at nucleosomes, surrounding the transcription start sites (TSSs) of both active and poised gene promoters. In addition, H2A.Z spreads across the entire promoter of inactive genes in a deacetylated state. In contrast, acH2A.Z is only localized at the TSSs of active genes. Gene deregulation in cancer is also associated with a reorganization of acH2A.Z and H2A.Z nucleosome occupancy across the promoter region and TSS of genes. Notably, in cancer cells we find that a gain of acH2A.Z at the TSS occurs with an overall decrease of H2A.Z levels, in concert with oncogene activation. Furthermore, deacetylation of H2A.Z at TSSs is increased with silencing of tumor suppressor genes. We also demonstrate that acH2A.Z anti-correlates with promoter H3K27me3 and DNA methylation. We show for the first time, that acetylation of H2A.Z is a key modification associated with gene activity in normal cells and epigenetic gene deregulation in tumorigenesis

ChromDB: The Chromatin Database

The ChromDB website (http://www.chromdb.org) displays chromatin-associated proteins, including RNAi-associated proteins, for a broad range of organisms. Our primary focus is to display sets of highly curated plant genes predicted to encode proteins associated with chromatin remodeling. Our intent is to make this intensively curated sequence information available to the research and teaching communities in support of comparative analyses toward understanding the chromatin proteome in plants, especially in important crop species such as corn and rice. Model animal and fungal proteins are included in the database to facilitate a complete, comparative analysis of the chromatin proteome and to make the database applicable to all chromatin researchers and educators. Chromatin biology and chromatin remodeling are complex processes involving a multitude of proteins that regulate the dynamic changes in chromatin structure which either repress or activate transcription. We strive to organize ChromDB data in a straightforward and comparative manner to help users understand the complement of proteins involved in packaging DNA into chromatin