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  • 1
    Electronic Resource
    Electronic Resource
    Heterochromatin protein 1 binds transgene arrays (1998)
    Springer
    Chromosoma 107 (1998), S. 286-292 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Heterochromatin protein 1 (HP1) of Drosophila and its homologs in vertebrates are key components of constitutive heterochromatin. Here we provide cytological evidence for the presence of heterochromatin within a euchromatic chromosome arm by immunolocalization of HP1 to the site of a silenced transgene repeat array. The amount of HP1 associated with arrays in polytene chromosomes is correlated with the array size. Inverted transposons within an array or increased proximity of an array to blocks of naturally occurring heterochromatin may increase transgene silencing without increasing HP1 labeling. Less dense anti-HP1 labeling is found at transposon arrays in which there is no transgene silencing. The results indicate that HP1 targets the chromatin of transposon insertions and binds more densely at a site with repeated sequences susceptible to heterochromatin formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004120050310
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of Drosophila heterochromatin (1976)
    Springer
    Chromosoma 57 (1976), S. 351-375 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A number of preliminary experiments have shown that the fluorescence pattern of Hoechst 33258, as opposed to that of quinacrine, varies with the concentration of dye. The metaphase chromosomes of D. melanogaster, D. simulans, D. virilis, D. texana, D. hydei and D. ezoana have therefore been stained with two concentrations of H 33258 (0.05 and 0.5 μg/ml in phosphate buffer at pH 7) and with a single concentration of quinacrine (0.5% in absolute alcohol). The three fluorescence patterns so obtained were shown to be somewhat different in some of the species and the coincide in others. All three stainings gave an excellent longitudinal differentiation of heterochromatin while euchromatin fluoresced homogeneously. — Living ganglion cells of the six species mentioned above were treated with quinacrine and H 33258. Quinacrine induced a generalized lengthening and swelling of the chromosomes and H 33258 the decondensation of specific heterochromatic regions. — A correlation of the base composition of the satellite DNAs contained in the heterochromatin of the species studied with the relative fluorescence and decondensation patterns showed that: 1) the extremely fluorochrome bright areas and those decondensed are present only in species containing AT rich satellite DNA; 2) the opposite is not true since some AT-rich satellite DNAs are neither fluorochrome bright nor decondensed; 3) there is no good correspondence between Hoechst bright areas and the decondensed ones. — AT richness therefore appears to be a necessary but not sufficient condition both for bright fluorescence and decondensation. Some cytological evidence suggests that similarly AT rich satellite DNA's respond differently in fluorescence and decondensation because they are bound to different chromosomal proteins. — A combination of the results of fluorescence and decondensation revealed at least 14 types of heterochromatin; 4–7 of which are simultaneously present in the same species. Since closely related species (i.e. D. melanogaster and D. simulans; D. virilis and D. texana) show marked differences in the heterochromatic types they contain, it can be suggested that within the genus Drosophila qualitative variations of heterochromatin have played an important role in speciation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00332160
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  • 3
    Electronic Resource
    Electronic Resource
    Interaction systems between heterochromatin and euchromatin inDrosophila melanogaster (1994)
    Springer
    Genetica 94 (1994), S. 267-274 
    Details
    ISSN: 1573-6857
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The constitutive heterochromatin is still one of the major unsolved problems in genetics. InDrosophila melanogaster three genetic systems involving specific interactions between heterochromatic and euchromatic genetic elements are known: the Segregation Distortion, thecrystal-Stellate and theabo-ABO systems. The genetic and molecular analysis of each system will allow the identification of all the components and the elucidation of the mechanisms underlying their interactions. The results of this analysis should provide insights into the biological significance of heterochromatin and into the evolutionary forces that result in the maintainance and stability of this enigmatic genetic material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01443440
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  • 4
    Electronic Resource
    Electronic Resource
    Cytological dissection of sex chromosome heterochromatin of Drosophila hydei (1981)
    Springer
    Chromosoma 84 (1981), S. 391-403 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Prophase chromosomes of Drosophila hydei were stained with 0.5 μg/ml Hoechst 33258 and examined under a fluorescence microscope. While autosomal and X chromosome heterochromatin are homogeneously fluorescent, the entirely heterochromatic Y chromosome exhibits an extremely fine longitudinal differentiation, being subdivided into 18 different regions defined by the degree of fluorescence and the presence of constrictions. Thus high resolution Hoechst banding of prophase chromosomes provides a tool comparable to polytene chromosomes for the cytogenetic analysis of the Y chromosome of D. hydei. — D. hydei heterochromatin was further characterized by Hoechst staining of chromosomes exposed to 5-bromodeoxyuridine for one round of DNA replication. After this treatment the pericentromeric autosomal heterochromatin, the X heterochromatin and the Y chromosome exhibit numerous regions of lateral asymmetry. Moreover, while the heterochromatic short arms of the major autosomes show simple lateral asymmetry, the X and the Y heterochromatin exhibit complex patterns of contralateral asymmetry. These observations, coupled with the data on the molecular content of D. hydei heterochromatin, give some insight into the chromosomal organization of highly and moderately repetitive heterochromatic DNA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00286028
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  • 5
    Electronic Resource
    Electronic Resource
    Characterization of Drosophila heterochromatin (1976)
    Springer
    Chromosoma 57 (1976), S. 377-386 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The C- and N-banding patterns of D. melanogaster, D. simulans, D. virilis, D. texana, D. ezoana and D. hydei were studied in comparison with quinacrine and Hoechst banding patterns. In all these Drosophila species the C bands correspond to the heterochromatin as revealed by the positive heteropycnosis in the prometaphase chromosomes. The N bands have the following characteristics: 1) they are always localized on the heterochromatin and generally do not correspond to the C bands; 2) they do not correspond to the nucleolar organizing regions; 3) they are inversely correlated with fluorescence, i.e., they correspond to regions which are scarcely, if at all, fluorescent after Hoechst 33258 or quinacrine staining; 4) they are localized both on regions containing AT rich satellite DNA and on those containing GC rich satellite DNA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00332161
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  • 6
    Electronic Resource
    Electronic Resource
    Cytological analysis of chromosomes in the two species Parascaris univalens and P. equorum (1986)
    Springer
    Chromosoma 94 (1986), S. 1-10 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Chromosome organization and the phenomenon of “chromatin diminution” in the two species Parascaris univalens (2n=2) and P. equorum (2n=4) were cytologically analysed by a variety of staining techniques (Quinacrine, Hoechst 33258, Chromomycin A3 and C-banding). The results show that: (1) the chromosomes of the two species differ markedly in both the location and the type of heterochromatin they contain; (2) in both species there is a strong chromosome polymorphism which, however, ranges within a basic species-specific phenotype; (3) the heterochromatin can be eliminated in presomatic cells during early embryogenesis at two different stages and in both cases the consequence of this process is the generation of somatic cells with a 2n=60 karyotype. Moreover, evidence suggesting the sterility of hybrids between the two species is provided.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293524
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  • 7
    Electronic Resource
    Electronic Resource
    Cytological and genetic analysis of the Y chromosome of Drosophila melanogaster (1983)
    Springer
    Chromosoma 88 (1983), S. 349-373 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract By applying quinacrine-, Hoechst- and N-banding techniques to neuroblast prometaphase chromosomes the Y chromosome of Drosophila melanogaster can be differentiated into 25 regions defined by the degree of fluorescence, the stainability after N-banding and the presence of constrictions. Thus these banding techniques provide an array of cytological landmarks along the Y chromosome that makes it comparable to a polytene chromosome for cytogenetic analysis. — 206 Y-autosome translocations (half of them carrying Y-linked sterile mutations) and 24 sterile y + Y chromosomes were carefully characterized by these banding techniques and used in extensive complementation analyses. The results of these experiments showed that: (1) there are four linearly ordered fertility factors in Y L and two fertility factors in Y S . (2) These fertility factors map to characteristic regions of the Y chromosome, specifically stained with the N-banding procedure. (3) The most extensively analyzed fertility factors are defined by a series of cytologically non-overlapping and genetically noncomplementing breaks and deficiencies distributed over large chromosome regions. For example, the breakpoints which inactivate the kl-5 and ks-1 loci are scattered along regions that contain about 3,000 kilobases (kb) DNA. Since these enormous regions formally define single genetic functions, the fertility genes of the Y chromosome have an as yet unappreciated physical dimension, being larger than euchromatic genes by two orders of magnitude.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00285858
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  • 8
    Electronic Resource
    Electronic Resource
    Carnitine suppression of position-effect variegation in Drosophila melanogaster (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 588-595 
    Details
    ISSN: 1617-4623
    Keywords: Position effect variegation ; Carnitine Butyrate ; Histone hyperacetylation ; Drosophila melanogaster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Carnitine is a well-known naturally occurring compound, very similar to butyrate, with an essential role in intermediary metabolism mainly at the mitochondrial level. Since butyrate inhibits the enzyme histone deacetylase and is capable of suppressing position-effect variegation in Drosophila melanogaster, we tested a further possible function of carnitine in the nucleus, using an assay for the suppression of position-effect variegation. We tested three physiological forms of carnitine (l-carnitine, l-propionylcarnitine, l-acetylcarnitine) for the ability to suppress two different chromosomal rearrangements, inducing variegation of the white + and brown + genes. The results show that the carnitine derivatives are capable of suppressing the position-effect variegation, albeit with different efficiencies. The carnitine derivatives interact lethally with Su-var(2)1 01, a mutation that induces hyperacetylation of histones, whilst hyperacetylated histories accumulated in both the nuclei of HeLa cells and Drosophila polytene chromosomes treated with the same compounds. These results strongly suggest that the carnitine derivatives suppress position-effect variegation by a mechanism similar to that of butyrate. It is suggested that carnitines may have a functional role in the nucleus, probably at the chromatin level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00282748
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  • 9
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    The Hsp70 chaperone is a major player in stress-induced transposable element activation (2019)
    National Academy of Sciences
    Details
    Publication Date: 2019-08-09
    Description: Previous studies have shown that heat shock stress may activate transposable elements (TEs) in Drosophila and other organisms. Such an effect depends on the disruption of a chaperone complex that is normally involved in biogenesis of Piwi-interacting RNAs (piRNAs), the largest class of germline-enriched small noncoding RNAs implicated in the epigenetic silencing of TEs. However, a satisfying picture of how chaperones could be involved in repressing TEs in germ cells is still unknown. Here we show that, in Drosophila, heat shock stress increases the expression of TEs at a posttranscriptional level by affecting piRNA biogenesis through the action of the inducible chaperone Hsp70. We found that stress-induced TE activation is triggered by an interaction of Hsp70 with the Hsc70−Hsp90 complex and other factors all involved in piRNA biogenesis in both ovaries and testes. Such interaction induces a displacement of all such factors to the lysosomes, resulting in a functional collapse of piRNA biogenesis. This mechanism has clear evolutionary implications. In the presence of drastic environmental changes, Hsp70 plays a key dual role in increasing both the survival probability of individuals and the genetic variability in their germ cells. The consequent increase of genetic variation in a population potentiates evolutionary plasticity and evolvability.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 10
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    Heterochromatin protein 1 interacts with 5′UTR of transposable element ZAM in a sequence-specific fashion (2007)
    Elsevier
    Details
    Publication Date: 2007-05-01
    Print ISSN: 0378-1119
    Electronic ISSN: 1879-0038
    Topics: Biology
    Published by Elsevier
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