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Positive regulation of euchromatic gene expression by HP1
No full textHP1 is a conserved prototype protein that plays an essential role in heterochromatin formation and epigenetic gene silencing through its interaction with histone methyltransferase enzymes (HMTases) and the histone H3 at lysine 9 (H3-MeK9). HP1 is also involved in telomere capping and, more surprisingly, in positive regulation of gene expression. Recently, a wide expression analysis, using a RIP-chip assays (RNA-immunoprecipitation on microarrays), has shown that HP1 associates with the transcripts of more than one hundred euchromatic genes and interacts with the heterogeneous nuclear ribonucleoproteins (hnRNPs) that are known to be involved in RNA processing. By these results, HP1 seems to be part of a complex that stabilizes RNA transcripts. Though previously unsuspected, it was also found that HP1-interacting hnRNPs have a functional role in heterochromatin formation. These proteins bind heterochromatin and are dominant suppressors of position effect variegation. Taken together, the results in the paper by Piacentini et al. open a window on a possible new conceptual landscape in which similar epigenetic mechanisms could have a significant role, both in the metabolism of RNA transcripts and in heterochromatin formation, producing opposite functional effects. These data seem to establish a functional link between euchromatin and heterochromatin
Heterochromatin protein 1 (HP1) is intrinsically required for post-transcriptional regulation of Drosophila Germline Stem Cell (GSC) maintenance
Full text linkA very important open question in stem cells regulation is how the fine balance between GSCs self-renewal and differentiation is orchestrated at the molecular level. In the past several years much progress has been made in understanding the molecular mechanisms underlying intrinsic and extrinsic controls of GSC regulation but the complex gene regulatory networks that regulate stem cell behavior are only partially understood. HP1 is a dynamic epigenetic determinant mainly involved in heterochromatin formation, epigenetic gene silencing and telomere maintenance. Furthermore, recent studies have revealed the importance of HP1 in DNA repair, sister chromatid cohesion and, surprisingly, in positive regulation of gene expression. Here, we show that HP1 plays a crucial role in the control of GSC homeostasis in Drosophila. Our findings demonstrate that HP1 is required intrinsically to promote GSC self-renewal and progeny differentiation by directly stabilizing the transcripts of key genes involved in GSCs maintenanc
Chromosomal distribution of Heterochromatin Protein1 (HP1) in Drosophila: a cytological map of euchromatin HP1 binding sites
No full textThe Heterochromatin Protein 1 (HP1) is a conserved protein which is best known for its strong association with the heterochromatin of Drosophila melanogaster. We previously demonstrated that another important property of HP1 is its localization to the telomeres of Drosophila, a feature that reflects its critical function as a telomere capping protein. Here we report our analysis of the euchromatic sites to which HP1 localizes. Using an anti-HP1 antibody, we compared immunostaining patterns on polytene chromosomes of the Ore-R wild type laboratory strain and four different natural populations. HP1 was found to accumulate at specific euchromatic sites, with a subset of the sites conserved among strains. These sites do not appear to be defined by an enrichment of known repetitive DNAs. Comparisons of HP1 patterns among several Drosophila species revealed that association with specific euchromatic regions, heterochromatin and telomeres is a conserved characteristic of HP1. Based on these results, we argue that HP1 serves a broader function than typically postulated. In addition to its role in heterochromatin assembly and telomere stability, we propose that HP1 plays an important role in regulating the expression of many different euchromatic regions
The Heterochromatin protein 1 (HP1) is involved in germline stem cells maintenance
No full textHP1 (Heterochromatin Protein 1) is a nonhistone chromosomal protein first discovered in Drosophila melanogaster by its association with the heterochromatin and through mutations that suppressed the silencing effect of heterochromatin in position-effect variegation. Numerous studies have shown that such protein is phylogenetically highly conserved and play a role in heterochromatin formation and gene silencing in many organisms. More recently, cytogenetical and molecular studies, performed in Drosophila and in other organisms, have revealed that HP1 associates also with telomeres and multiple euchromatic sites. All these studies collectively have shown that these three different positions are related to three different functions of HP1: heterochromatin formation and gene silencing, telomeric capping and silencing, and positive control of gene expression.
Since it has been observed that HP1 is highly abundant in adult ovaries and testis, we have performed studies to test if this abundance could be related to its involvement in germ stem cell (GSC) regulation.
We will presents the results of our experiments showing that HP1 is involved in GSC maintainance and transposon silencing
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Hsp90 and its interacting partners in the piRNAs pathway
No full textHsp90 is a molecular chaperone stabilizing many key regulatory proteins. Recently it was shown that the functional alteration of Hsp90 causes activation of transposons in Drosophila germ cells due to alterations in the piRNA pathway. This disfunction results in the induction of a series of phenotypic variants. Therefore Hsp90 works as suppressor of variability that can be generated by the movement of transposons.
Preliminary experiments show that the "heat shock" treatment activates the movement of transposons in Drosophila thus suggesting that stress may trigger a functional shift of Hsp90.
To address this point, we performed experiments whose results strongly suggest that a functional shift of Hsp90 induced by stress could be related to the involvement of Hsp90 in complexes that are different in normal and stress conditions. In other words, Hsp90 functions in piRNA pathway in absence of stress, but under stress conditions, its role changes by its interaction with different factors.
A further result obtained in this work is the involvement of GW182 in piRNA pathway. GW182 interact with Hsp90 and localizes in nuage where piRNA biogenesis occurs. In addition, Hsp90 disfunction causes GW182 and Vasa delocalization from nuage. Therefore we can speculate that, in piRNA pathway, the functions of these three proteins are interconnected
Drosophilidae monitoring in Apulia (Italy) reveals Drosophila suzukii as one of the four most abundant species
No full textThe knowledge of the endemic drosophilid assemblage is a useful reference to study population dynamics when new species are introduced in a geographical area. The introduction of invasive species can change the structure of the drosophilid community; hence, the distribution data for endemic species are also essential to support efficient pest management. We provide the first description of the natural drosophilid populations (Diptera Drosophilidae) recorded in Apulia, in Southern Italy. The flies, which were collected in a field survey throughout a year, were classified by morphological and molecular analyses by sequencing the barcode fragment of the COI mtDNA gene. The identified species show a distribution of frequencies that varies throughout the year, reflecting a seasonal life cycle peculiar to each species. Among the recorded drosophilids, the potential pest species Drosophila suzukii represents one of the four most abundant species
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