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1.
Veiseth SV Rahman MA Yap KL Fischer A Egge-Jacobsen W Reuter G Zhou MM Aalen RB Thorstensen T 《PLoS genetics》2011,7(3):e1001325
Chromatin structure and gene expression are regulated by posttranslational modifications (PTMs) on the N-terminal tails of histones. Mono-, di-, or trimethylation of lysine residues by histone lysine methyltransferases (HKMTases) can have activating or repressive functions depending on the position and context of the modified lysine. In Arabidopsis, trimethylation of lysine 9 on histone H3 (H3K9me3) is mainly associated with euchromatin and transcribed genes, although low levels of this mark are also detected at transposons and repeat sequences. Besides the evolutionarily conserved SET domain which is responsible for enzyme activity, most HKMTases also contain additional domains which enable them to respond to other PTMs or cellular signals. Here we show that the N-terminal WIYLD domain of the Arabidopsis SUVR4 HKMTase binds ubiquitin and that the SUVR4 product specificity shifts from di- to trimethylation in the presence of free ubiquitin, enabling conversion of H3K9me1 to H3K9me3 in vitro. Chromatin immunoprecipitation and immunocytological analysis showed that SUVR4 in vivo specifically converts H3K9me1 to H3K9me3 at transposons and pseudogenes and has a locus-specific repressive effect on the expression of such elements. Bisulfite sequencing indicates that this repression involves both DNA methylation-dependent and -independent mechanisms. Transcribed genes with high endogenous levels of H3K4me3, H3K9me3, and H2Bub1, but low H3K9me1, are generally unaffected by SUVR4 activity. Our results imply that SUVR4 is involved in the epigenetic defense mechanism by trimethylating H3K9 to suppress potentially harmful transposon activity. 相似文献
2.
Samaiya A Deo SS Thulkar S Hazarika S Kumar S Parida DK Shukla NK 《World journal of surgical oncology》2005,3(1):3-7
BACKGROUND: Malignant small bowel tumors are very rare and leiomyosarcoma accounts for less than 15% of the cases. Management of these tumors is challenging in view of nonspecific symptoms, unusual presentation and high incidence of metastasis. In this case report, an unusual presentation of jejunal sarcoma and management of liver metastasis with radiofrequency ablation (RFA) is discussed. CASE PRESENTATION: A 45-year-old male presented with anemia and features of small bowel obstruction. Operative findings revealed a mass lesion in jejunum with intussusception of proximal loop. Resection of bowel mass was performed. Histopathological findings were suggestive of leiomyosarcoma. After 3-years of follow-up, the patient developed recurrence in infracolic omentum and a liver metastasis. The omental mass was resected and liver lesion was managed with radiofrequency ablation. CONCLUSION: Jejunal leiomyosarcoma is a rare variety of malignant small bowel tumor and a clinical presentation with intussusception is unusual. We suggest that an aggressive management approach using a combination of surgery and a newer technique like RFA can be attempted in patients with limited metastatic spread to liver to prolong the long-term survival in a subset of patients. 相似文献
3.
JINDŘIŠKA BOJKOVÁ KLÁRA KOMPRDOVÁ TOMÁŠ SOLDÁN SVĚTLANA ZAHRÁDKOVÁ 《Freshwater Biology》2012,57(12):2550-2567
1. Rapid expansion and intensification of anthropogenic activities in the 20th century has caused profound changes in freshwater assemblages. Unfortunately, knowledge of the extent and causes of species loss (SL) is limited due to the lack of reliable historical data. An unusual data set allows us to compare changes in the most sensitive of aquatic insect orders, the Plecoptera, at some 170 locations in the Czech Republic between two time periods, 1955–1960 and 2006–2010. Historical data (1890–1911) on assemblages of six lowland rivers allow us to infer even earlier changes. 2. Regional stonefly diversity decreased in the first half of the 20th century. Streams at lower altitudes lost a substantial number of species, which were never recovered. In the second half of the century, large‐scale anthropogenic pressure caused SL in all habitats, leading to a dissimilarity of contemporary and previous assemblages. The greatest changes were found at sites affected by organic pollution and a mixture of organic pollution and channelisation or impoundment. Colonisation of new habitats was observed in only three of the 80 species evaluated. 3. Species of moderate habitat specialisation and tolerance to organic pollution were most likely to be lost. Those with narrow specialisations in protected habitats were present in both historical and contemporary collections. 4. Contemporary assemblages are the consequence of more than a 100 years of anthropogenic impacts. In particular, streams at lower altitude and draining intensively exploited landscapes host a mere fragment of the original species complement. Most stonefly species are less frequently present than before, although their assemblages remain almost intact in near‐natural mountain streams. Our analyses demonstrate dramatic restriction of species ranges and, in some cases, apparent changes in altitudinal preference throughout the area. 相似文献
4.
Moderate alcohol consumption is associated with better endothelial function: a cross sectional study
Keiko Suzuki Mitchell SV Elkind Bernadette Boden-Albala Zhezhen Jin Grace Berry Marco R Di Tullio Ralph L Sacco Shunichi Homma 《BMC cardiovascular disorders》2009,9(1):1-5
Background
Natural heterologous valved conduits with a diameter greater than 22 mm that can be used for right ventricular outflow tract reconstruction in adults are not commercially available. The purpose of this study was to measure by ultrasonography the maximum diameter of the distended jugular veins of horses and cattle, respectively, to identify a population of animals that would be suitable for post-mortem collection of jugular veins at sizes greater than 22 mm.Methods
The study population included 60 Warmblood horses, 25 Freiberger horses, 20 Brown Swiss cows, and 20 Holstein cows (including 10 Holstein and 10 Red Holstein). The maximum cross-sectional diameter of the distended jugular veins was measured at a location half-way between the mandibular angle and the thoracic inlet. The thoracic circumference (heart girth length) was used as a surrogate of body size. The jugular vein diameters of the different populations were compared by analysis of variance and the association between heart girth length and jugular vein diameter was determined in each of the four study populations by linear regression analysis.Results
There was considerable individual variation of jugular vein diameters within each of the four study populations. There was no statistically significant relationship between thoracic circumference and jugular vein diameter in any of the populations. The jugular vein diameters of Brown Swiss cows were significantly larger than those of any of the other populations. Warmblood horses had significantly larger jugular vein diameters compared to Freiberger horses.Conclusion
The results of this study suggest that the production of bovine or equine xenografts with diameters of greater than 22 mm would be feasible. Differences between species and breeds need to be considered. However, prediction of the jugular vein diameter based on breed and heart girth length in an individual animal is inaccurate. 相似文献5.
Hoppmann V Thorstensen T Kristiansen PE Veiseth SV Rahman MA Finne K Aalen RB Aasland R 《The EMBO journal》2011,30(10):1939-1952
Post-translational modifications of the N-terminal histone tails, including lysine methylation, have key roles in regulation of chromatin and gene expression. A number of protein modules have been identified that recognize differentially modified histone tails and provide their proteins with the capacity to sense such modifications. Here, we identify the CW domain of plant and animal chromatin-related proteins as a novel module that recognizes different methylated states of lysine 4 on histone H3 (H3K4me). The solution structure of the CW domain of the Arabidopsis ASH1 HOMOLOG2 (ASHH2) histone methyltransferase provides insight into how different CW domains can distinguish different methylated histone tails. We provide evidence that ASHH2 is acting on H3K4me-marked genes, allowing for ASHH2-dependent H3K36 tri-methylation, which contributes to sustained expression of tissue-specific and developmentally regulated genes. This suggests that ASHH2 is a combined 'reader' and 'writer' of the histone code. We propose that different CW domains, dependent on their specificity for different H3K4 methylations, are important for epigenetic memory or participate in switching between permissive and repressive chromatin states. 相似文献
6.
Thomas GH; Newbern EC; Korte CC; Bales MA; Muse SV; Clark AG; Kiehart DP 《Molecular biology and evolution》1997,14(12):1285-1295
Many structural, signaling, and adhesion molecules contain tandemly
repeated amino acid motifs. The alpha-actinin/spectrin/dystrophin
superfamily of F-actin-crosslinking proteins contains an array of triple
alpha-helical motifs (spectrin repeats). We present here the complete
sequence of the novel beta-spectrin isoform beta(Heavy)- spectrin (beta H).
The sequence of beta H supports the origin of alpha- and beta-spectrins
from a common ancestor, and we present a novel model for the origin of the
spectrins from a homodimeric actin-crosslinking precursor. The pattern of
similarity between the spectrin repeat units indicates that they have
evolved by a series of nested, nonuniform duplications. Furthermore, the
spectrins and dystrophins clearly have common ancestry, yet the repeat unit
is of a different length in each family. Together, these observations
suggest a dynamic period of increase in repeat number accompanied by
homogenization within each array by concerted evolution. However, today,
there is greater similarity of homologous repeats between species than
there is across repeats within species, suggesting that concerted evolution
ceased some time before the arthropod/vertebrate split. We propose a
two-phase model for the evolution of the spectrin repeat arrays in which an
initial phase of concerted evolution is subsequently retarded as each new
protein becomes constrained to a specific length and the repeats diverge at
the DNA level. This evolutionary model has general applicability to the
origins of the many other proteins that have tandemly repeated motifs.
相似文献
7.
Comparisons of the molecular evolutionary process at rbcL and ndhF in the grass family (Poaceae) 总被引:2,自引:1,他引:1
We examine rate heterogeneity among evolutionary lineages of the grass
family at two plasmid loci, ndhF and rbcL, and we introduce a method to
determine whether patterns of rate heterogeneity are correlated between
loci. We show both that rates of synonymous evolution are heterogeneous
among grass lineages and that are heterogeneity is correlated between loci
at synonymous sites. At nonsynonymous sites, the pattern of rate
heterogeneity is not correlated between loci, primarily due to an aberrant
pattern of rate heterogeneity at nonsynonymous sites of rbcL. We compare
patterns of synonymous rate heterogeneity to predictors based on the
generation time effect and the speciation rate hypotheses. Although there
is some evidence for generation time effects, neither generation time
effects nor speciation rates appear to be sufficient to explain patterns of
rate heterogeneity in the grass plastid sequences.
相似文献
8.
9.
Hannah Gardener Della David Morte Mitchell SV Elkind Ralph L Sacco Tatjana Rundek 《BMC cardiovascular disorders》2009,9(1):1-8
Background
Heterogeneity in B-type natriuretic peptide (BNP) levels, especially among individuals with acute heart failure with normal left ventricular ejection fraction (HFNEF), can cause confusion in interpreting results. We investigated the characteristics of cases of acute HFNEF with only modestly elevated BNP.Methods
One hundred forty-two patients with acute or acute exacerbation of chronic HFNEF were divided into two groups by BNP level: BNP < 100 pg/ml (NB group, n = 45) and BNP ≥ 100 pg/ml (B group, n = 97). We compared clinical findings, echocardiography results, and neurohormonal factors between these two groups.Results
In the NB group, a history of open-heart surgery (OHS) was more frequent (71% vs. 22%, p < 0.0001) and hypertension was less frequent (p = 0.0005). Left atrial diameter (LAd) was higher (p = 0.0026), while interventricular septal thickness, posterior wall thickness, relative wall thickness, left ventricular mass index were lower (p = 0.0005, p = 0.0225, p = 0.0114, p = 0.0051, respectively) in the NB group. In patients with HFNEF, a history of OHS remained an independent predictor of BNP level (< 100 pg/ml) after adjustment for hypertension, age, LAd, and interventricular septal thickness (odds ratio 3.6, p = 0.0252).Conclusion
We found associations between acute HFNEF with less elevated BNP and a history of OHS. In a patient suspected of HFNEF, a history of OHS is considered diagnostic evidence of presence of diastolic heart failure when plasma levels of BNP are less elevated. 相似文献10.
Diaz-Perez, S. V., Crouch, V. W., and Orbach, M. J. 1996. Construction and characterization of a Magnaporthe grisea bacterial artificial chromosome library. Fungal Genet. Biol. 20, 280-288. A bacterial artificial chromosome (BAC) library of Magnaporthe grisea containing 4128 clones with an average insert size of 66-kb has been constructed. This library represents seven genome equivalents of M. grisea and has been demonstrated to be representative of the genome by screening for the presence of several single-copy genes and DNA markers. The utility of the library for use in map-based cloning projects was shown by the spanning of a nine-cosmid, 207-kb DNA contig with only 3 BAC clones. In addition, using a lys1-3 auxotroph, we have shown that BAC clones at least 113 kb can be transformed into M. grisea to screen for complementation of mutations. Thus, BACs isolated in chromosome walks can be rapidly screened for the presence of the sought after gene. The ease of construction of BAC libraries and of isolation and manipulation of BAC clones makes the BAC system an ideal one for physical analyses of fungal genomes. 相似文献