Identification of chromosomal actin in insect cells: Structural and functional significance

1994 ◽  
Vol 52 ◽  
pp. 16-17
Author(s):  
Ivo Sauman
Keyword(s):  
Insect Cells ◽  
Polytene Chromosomes ◽  
Follicle Cell ◽  
Nuclear Actin ◽  
Cell Nuclei ◽  
Antibody Staining ◽  
Eukaryotic Nucleus ◽  
Biochemical Studies ◽  
First Time ◽  
Endonuclease Digestion

The non-histone proteins associated with eukaryotic nuclear chromatin are incompletely characterized and their function is poorly understood. Thirty years ago, the presence of actin in the eukaryotic nucleus was reported for first time. Since then, several biochemical studies have identified actin and myosin as significant constituents of isolated nuclear matrix from a variety of cells. The studies cited above and others make a strong case for presence of actin in nuclei, but do not implicate actin as a component of eukaryotic chromosomes.Our examination of cells associated with developing ovarian follicles of lepidopterans confirmed that under routine immunocytochemical conditions, no actin can be detected with anti-actin antibodies in the follicle cell nuclei (Fig. 1a) . However, Fig. 1b demonstrates that endonuclease pretreatment of the same preparation to remove DNA followed by anti-actin antibody staining uncovers the presence of nuclear actin. Moreover, by employing squash preparations of Drosophila salivary glands and the same endonuclease digestion, it is clear that the nuclear actin is directly associated with the polytene chromosomes (Fig. 2a,b).

scholarly journals Arp2/3 and Unc45 maintain heterochromatin stability in Drosophila polytene chromosomes

2019 ◽  
Author(s):  
George Dialynas ◽  
Laetitia Delabaere ◽  
Irene Chiolo
Keyword(s):  
Actin Filaments ◽  
Genome Stability ◽  
Actin Polymerization ◽  
Cultured Cells ◽  
Nuclear Periphery ◽  
Polytene Chromosomes ◽  
Nuclear Actin ◽  
Nuclear Dynamics ◽  
Ectopic Recombination ◽  
Repair Pathways

AbstractRepairing DNA double-strand breaks (DSBs) is particularly challenging in pericentromeric heterochromatin, where the abundance of repeated sequences exacerbates the risk of ectopic recombination. InDrosophilaKc cells, accurate homologous recombination (HR) repair of heterochromatic DSBs relies on the relocalization of repair sites to the nuclear periphery before Rad51 recruitment and strand invasion. This movement is driven by Arp2/3-dependent nuclear actin filaments and myosins’ ability to walk along them. Conserved mechanisms enable the relocalization of heterochromatic DSBs in mouse cells, and their defects lead to massive ectopic recombination in heterochromatin and chromosome rearrangements. InDrosophilapolytene chromosomes, extensive DNA movement is blocked by a stiff structure of chromosome bundles. Repair pathways in this context are poorly characterized, and whether heterochromatic DSBs relocalize in these cells is unknown. Here, we show that damage in heterochromatin results in relaxation of the heterochromatic chromocenter, consistent with a dynamic response in this structure. Arp2/3, the Arp2/3 activator Scar, and the myosin activator Unc45, are required for heterochromatin stability in polytene cells, suggesting that relocalization enables heterochromatin repair in this tissue. Together, these studies reveal critical roles for actin polymerization and myosin motors in heterochromatin repair and genome stability across different organisms and tissue types.Impact StatementHeterochromatin relies on dedicated pathways for ‘safe’ recombinational repair. In mouse and fly cultured cells, DNA repair requires the movement of repair sites away from the heterochromatin ‘domain’vianuclear actin filaments and myosins. Here, we explore the importance of these pathways inDrosophilasalivary gland cells, which feature a stiff bundle of endoreduplicated polytene chromosomes. Repair pathways in polytene chromosomes are largely obscure and how nuclear dynamics operate in this context is unknown. We show that heterochromatin relaxes in response to damage, and relocalization pathways are necessary for repair and stability of heterochromatic sequences. This deepens our understanding of repair mechanisms in polytenes, revealing unexpected dynamics. It also provides a first understanding of nuclear dynamics responding to replication damage or rDNA breaks, providing a new understanding of the importance of the nucleoskeleton in genome stability. We expect these discoveries to shed light on tumorigenic processes, including therapy-induced cancer relapses.

Karyotype of Propsilocerus akamusi (Tokunaga) from China (Diptera: Chironomidae)

Zootaxa ◽  
2004 ◽  
Vol 765 (1) ◽  
pp. 1 ◽  
Author(s):  
IYA I. KIKNADZE ◽  
XINHUA WANG ◽  
ALBINA G. ISTOMINA
Keyword(s):  
Polytene Chromosomes ◽  
Banding Patterns ◽  
Chinese Populations ◽  
Data Support ◽  
Cytogenetic Data ◽  
Karyotype Structure ◽  
Chromosomal Polymorphisms ◽  
First Time

The karyotype structure and banding patterns of the polytene chromosomes of Propsilocerus akamusi from China are investigated for the first time. Photographic maps of the three chromosomes of P. akamusi are presented. Three heterochromatic blocks in the centromere regions are characteristic of this species. Chromosomal polymorphisms were not found in the Chinese populations. Cytogenetic data support the phylogenetic argument previously outlined for the genus.

scholarly journals How genes find their way inside the cell nucleus

2007 ◽  
Vol 179 (6) ◽  
pp. 1093-1094 ◽  
Author(s):  
Maria Carmo-Fonseca
Keyword(s):  
Cell Nucleus ◽  
Live Cell Imaging ◽  
Gene Locus ◽  
Recent Progress ◽  
Cell Imaging ◽  
Live Cell ◽  
Nuclear Actin ◽  
First Time

Recent progress in live cell imaging suggests a role for nuclear actin in chromatin movement. In this issue, for the first time, a gene locus moving toward a subnuclear compartment was tracked. Motion of the locus is actin dependent, raising the question of whether chromatin movements are random or directed.

The role of follicle cell nuclei in amphibian oocyte maturation

1989 ◽  
Vol 27 ◽  
pp. 160 ◽  
Author(s):  
M.N. Skoblina ◽  
O.T. Kondratieva ◽  
E.V. Orlov
Keyword(s):  
Oocyte Maturation ◽  
Follicle Cell ◽  
Cell Nuclei ◽  
Amphibian Oocyte

scholarly journals Structural and Biochemical Studies of Dihydrofolate Reductase from Streptococcus pyogenes as a Target for Antifolate Antibiotics

2018 ◽  
Author(s):  
Behnoush Hajian ◽  
Jolanta Krucinska ◽  
Michael Martins ◽  
Narendran G-Dayanan ◽  
Kishore Viswanathan ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Streptococcus Pyogenes ◽  
Dihydrofolate Reductase ◽  
Wide Spectrum ◽  
Streptococcal Infections ◽  
Biochemical Studies ◽  
Live Bacteria ◽  
Dhfr Inhibitors ◽  
First Time ◽  
Structural Insights

ABSTRACTStreptococcus pyogenes, a beta-hemolytic bacterium, causes a wide spectrum of infections in human including pharyngitis, tonsillitis, scarlet fever, rheumatic fever, and necrotizing fasciitis. Streptococcal infections can also exist as co-infection with methicillin resistant Staphylococcus aureus (MRSA). Trimethoprim-sulfamethoxazole (TMP-SMX) combination has been used for treatment of S. pyogenes and MRSA co-infection. However, resistance to TMP, an inhibitor of dihydrofolate reductase enzyme (DHFR), has challenged the efficacy of TMP-SMX combination. We explored the activity of a series of novel DHFR inhibitors against S. pyogenes. This study identified potent inhibitors of DHFR enzyme from S. pyogenes with excellent inhibitory activity against the growth of the live bacteria. We determined, for the first time, the crystal structure of S. pyogenes DHFR which provides structural insights into design and development of antifolate agents against this global pathogen.

scholarly journals Establishment of dorsal-ventral polarity of theDrosophilaegg requirescapicuaaction in ovarian follicle cells

Development ◽  
2001 ◽  
Vol 128 (22) ◽  
pp. 4553-4562 ◽  
Author(s):  
Deborah J. Goff ◽  
Laura A. Nilson ◽  
Donald Morisato
Keyword(s):  
Target Genes ◽  
Nuclear Translocation ◽  
Ovarian Follicle ◽  
Growth Factor Receptor ◽  
Follicle Cell ◽  
Dorsal Side ◽  
Follicle Cells ◽  
Follicular Epithelium ◽  
Egfr Signaling ◽  
Cell Nuclei

The dorsal-ventral pattern of the Drosophila egg is established during oogenesis. Epidermal growth factor receptor (Egfr) signaling within the follicular epithelium is spatially regulated by the dorsally restricted distribution of its presumptive ligand, Gurken. As a consequence, pipe is transcribed in a broad ventral domain to initiate the Toll signaling pathway in the embryo, resulting in a gradient of Dorsal nuclear translocation. We show that expression of pipe RNA requires the action of fettucine (fet) in ovarian follicle cells. Loss of maternal fet activity produces a dorsalized eggshell and embryo. Although similar mutant phenotypes are observed with regulators of Egfr signaling, genetic analysis suggests that fet acts downstream of this event. The fet mutant phenotype is rescued by a transgene of capicua (cic), which encodes an HMG-box transcription factor. We show that Cic protein is initially expressed uniformly in ovarian follicle cell nuclei, and is subsequently downregulated on the dorsal side. Earlier studies described a requirement for cic in repressing zygotic target genes of both the torso and Toll pathways in the embryo. Our experiments reveal that cic controls dorsal-ventral patterning by regulating pipe expression in ovarian follicle cells, before its previously described role in interpreting the Dorsal gradient.

scholarly journals Post-mitotic expansion of cell nuclei requires ACTN4-mediated nuclear actin filament bundling

2020 ◽  
Author(s):  
Sylvia Krippner ◽  
Jannik Winkelmeier ◽  
Carsten Schwan ◽  
Julian Knerr ◽  
David Virant ◽  
...  
Keyword(s):  
Actin Filament ◽  
Super Resolution ◽  
Mitotic Cell ◽  
Actin Binding ◽  
Nuclear Actin ◽  
Actin Assembly ◽  
Cell Nuclei ◽  
Cellular Processes ◽  
And Migration ◽  
Nuclear Expansion

AbstractThe actin cytoskeleton operates in a multitude of cellular processes including cell shape and migration, mechanoregulation, as well as membrane or organelle dynamics. However, its filamentous properties and functions inside the mammalian cell nucleus are less well explored. We previously described transient actin assembly at mitotic exit that promotes nuclear expansion during chromatin decondensation. Here, we identify non-muscle ACTN4 as a critical regulator to facilitate F-actin formation, reorganization and bundling during postmitotic nuclear expansion. ACTN4 binds to nuclear actin filaments and ACTN4 clusters associate with nuclear F-actin in a highly dynamic fashion. ACTN4 but not ACTN1 is required for proper postmitotic nuclear volume expansion, mediated by its actin binding domain. Using super-resolution imaging to quantify actin filament numbers and widths in individual nuclei we find that ACTN4 is necessary for postmitotic nuclear actin assembly and actin filament bundling. Our findings uncover a nuclear cytoskeletal function for ACTN4 to control nuclear size during mitotic cell division.

The polytene chromosomes of species of Eusimulium (Hellichiella) (Diptera: Simuliidae)

1983 ◽  
Vol 61 (6) ◽  
pp. 1220-1231 ◽  
Author(s):  
Klaus Rothfels ◽  
Victor I. Golini
Keyword(s):  
Salivary Gland ◽  
Banding Pattern ◽  
Polytene Chromosomes ◽  
James Bay ◽  
Diagnostic Features ◽  
First Time

In an extension of Dunbar's work (R. W. Dunbar. 1967. Can. J. Zool. 45: 377–396) eight species in Hellichiella were examined cytologically on the basis of the banding pattern of salivary gland polytene chromosomes. Hellichiella congareenarum, H. innocens, and H. anatinum were restudied. It was concluded that the sibling distinction between congareenarum and congareenarum 'b' stipulated by Dunbar is not tenable and that anatinum differs from standard by only one inversion (IIS-1). Species studied for the first time are H. rendalense (from Norway), H. latipes (syn. subexcisum from Britain) and H. saccai (from Italy), and the undescribed "Opinaca" sp. (from James Bay, Quebec), and "sp. near dogieli" (from Norway). Diagnostic features are given for each taxon in terms of (i) fixed inversions from standard (congareenarum), (ii) specific sex differential segments, and (iii) inversion polymorphisms. These features are utilized in the construction of an unrooted cytophylogeny.

Amino acids in the octocoralVeretillum cynomorium: the effect of seasonality and differences from scleractinian hexacorals

2012 ◽  
Vol 93 (4) ◽  
pp. 913-918 ◽  
Author(s):  
Miguel Baptista ◽  
Ana Luísa Maulvault ◽  
Katja Trübenbach ◽  
Luis Narciso ◽  
António Marques ◽  
...  
Keyword(s):  
Amino Acid ◽  
Principal Component ◽  
Dry Weight ◽  
Amino Acid Profile ◽  
Temporal Variations ◽  
Total Amino Acid ◽  
Interspecific Differences ◽  
Biochemical Studies ◽  
Almost All ◽  
First Time

The majority of biochemical studies in corals has been focused on the lipidic composition and little attention has been given to the amino acid profile of these invertebrates. The objectives of this work were to investigate, for the first time, the temporal variations in the total amino acid (AA) composition of an octocoral, namely the sea penVeretillum cynomorium, and to evaluate possible interspecific differences in AA profile between this octocoral and hexacorals. The quantitatively most important AAs inV. cynomoriumcolonies were: glutamic acid, varying from 3.92 to 5.94% dry weight (dw) and representing around 14–15% of total AA content; aspartic acid (3.34–4.99% dw; 11–12%); and glycine (2.87–4.57% dw; 9–12%). On the other hand, the minor AAs were methionine (0.41–0.73% dw; 1–2%) and histidine (0.54–0.76% dw; 2%). Almost all AAs showed the same significant seasonal variations, with the highest values in February, second highest in October and the lowest in June. Some AAs, namely lysine, phenylalanine and methionine did not follow this trend and showed the major peak in October. Most of the AA variations seemed to be linked to changes in food availability and/or gametogenesis. Principal component analysis clearly separated the octocoral from the group of hexacorals, mainly due to the higher percentages of arginine, tyrosine and glycine inV. cynomorium, and valine, serine, histidine, isoleucine and alanine in hexacorallia species. We speculate that this differentiation possibly derived from physiological differences related to phylogeny, and was not affected by reproductive or environmental seasonality.

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