The Landscape of Extrachromosomal DNA (ecDNA) in the Normal Hematopoiesis and Leukemia Evolution

2022 ◽  
Author(s):  
Tiansheng Zeng ◽  
Wenhui Huang ◽  
Longzhen Cui ◽  
Wenjuan Zhang ◽  
Qing Lin ◽  
...  
Keyword(s):  
Extrachromosomal Dna

Extrachromosomal DNA: Redefining the pathogenesis of glioblastoma

2021 ◽  
Vol 1876 (1) ◽  
pp. 188551
Author(s):  
Anjali Shiras ◽  
Abir Mondal
Keyword(s):  
Extrachromosomal Dna

scholarly journals Ku80-deficient Cells Exhibit Excess Degradation of Extrachromosomal DNA

1996 ◽  
Vol 271 (24) ◽  
pp. 14405-14411 ◽  
Author(s):  
Feng Liang ◽  
Maria Jasin
Keyword(s):  
Extrachromosomal Dna

scholarly journals Absence of rDNA amplification in the uninucleolate oocyte of the cockroach Blattella germanica (Oorthoptera: Blattidae).

1976 ◽  
Vol 71 (1) ◽  
pp. 49-58 ◽  
Author(s):  
M D Cave
Keyword(s):  
Ribosomal Rna ◽  
General Pattern ◽  
Blattella Germanica ◽  
Nucleolar Organizer ◽  
Extrachromosomal Dna ◽  
Total Dna ◽  
Cockroach Blattella Germanica ◽  
Rdna Amplification ◽  
Large Nucleolus

Amplification of the genes coding for ribosomal RNA oocurs in the oocytes of a wide variety of organisms. In oocytes of various species of crickets (Orthoptera: Gryllidae) the amplified DNA is contained in a large extrachromosomal DNA body. Multiple nucleoli form about the periphery of the DNA body during the diplotene stage of meiosis I. In contrast to the general pattern of orthopteran oocytes, oocytes of the cockroach Blattella germanica demonstrate a single large nucleolus instead of many nucleoli. In order to determine whether the genes coding for rRNA are amplified in the oocytes of B. germanica, the relative amount of rDNA in oocytes was compared with the rDNA content of spermatocytes and somatic cells. An extrachromosomal DNA body similar to that present in crickets is not present in B. germanica. A satellite DNA band which contains nucleotide sequences complementary to rRNA accounts for approximately 3-5% of the total DNA in somatic and in male and female gametogenic tissues. Female cells contain approximately twice as much rDNA as do male cells. An XX-XO sex-determining mechanism is operative in B. germanica. In situ hybridization with rRNA indicates that the nucleolar organizer is located on one end of the X chromosome and that oocytes do not contain more than twice the amount of rDNA found in spermato cytes. The data indicate that rDNA is not amplified in the uninucleolate oocyte of B germanica.

Extrachromosomal DNA elements of plant pathogenic mycoplasmalike organisms

1991 ◽  
Vol 13 (1) ◽  
pp. 26-32 ◽  
Author(s):  
A.S. Denes ◽  
R.C. Sinha
Keyword(s):  
Extrachromosomal Dna ◽  
Dna Elements ◽  
Mycoplasmalike Organisms

In organello replication and viral affinity of linear, extrachromosomal DNA of the ascomycete Ascobolus immersus

1989 ◽  
Vol 218 (3) ◽  
pp. 523-530 ◽  
Author(s):  
F. Kempken ◽  
F. Meinhardt ◽  
K. Esser
Keyword(s):  
Extrachromosomal Dna ◽  
In Organello ◽  
Ascobolus Immersus

Linear plasmids in Klebsiella and other Enterobacteriaceae

2021 ◽  
Author(s):  
Jane Hawkey ◽  
Hugh Cottingham ◽  
Alex Tokolyi ◽  
Ryan R Wick ◽  
Louise M Judd ◽  
...  
Keyword(s):  
Plasmid Stability ◽  
Bacterial Species ◽  
Salmonella Typhi ◽  
Multidrug Resistant ◽  
Linear Plasmid ◽  
Extrachromosomal Dna ◽  
Linear Plasmids ◽  
Future Studies ◽  
And Function

Linear plasmids are extrachromosomal DNA that have been found in a small number of bacterial species. To date, the only linear plasmids described in the Enterobacteriaceae family belong to Salmonella, first found in Salmonella Typhi. Here, we describe a collection of 12 isolates of the Klebsiella pneumoniae species complex in which we identified linear plasmids. We used this collection to search public sequence databases and discovered an additional 74 linear plasmid sequences in a variety of Enterobacteriaceae species. Gene content analysis divided these plasmids into five distinct phylogroups, with very few genes shared across more than two phylogroups. The majority of linear plasmid-encoded genes are of unknown function, however each phylogroup carried its own unique toxin-antitoxin system and genes with homology to those encoding the ParAB plasmid stability system. Passage in vitro of the 12 linear plasmid-carrying Klebsiella isolates in our collection (which include representatives of all five phylogroups) indicated that these linear plasmids can be stably maintained, and our data suggest they can transmit between K. pneumoniae strains (including members of globally disseminated multidrug resistant clones) and also between diverse Enterobacteriaceae species. The linear plasmid sequences, and representative isolates harbouring them, are made available as a resource to facilitate future studies on the evolution and function of these novel plasmids.

An Ultrastructural and Radioautographic Study of Early Oogenesis in the Toad Xenopus Laevis

1973 ◽  
Vol 12 (1) ◽  
pp. 71-93
Author(s):  
LESLEY WATSON COGGINS
Keyword(s):  
Electron Microscope ◽  
Xenopus Laevis ◽  
Thymidine Incorporation ◽  
Ultrastructural Level ◽  
Extrachromosomal Dna ◽  
Late Pachytene ◽  
Synaptonemal Complexes ◽  
Round Nucleus ◽  
A Cell ◽  
Major Period

Early oogenesis in the toad Xenopus laevis has been investigated at the ultrastructural level, with particular reference to the formation of extrachromosomal DNA. Thymidine incorporation was localized by electron microscope radioautography. In oogonia, the nucleus is irregular in outline and may contain several nucleoli. Oocytes, from premeiotic interphase to late pachytene, are found in cell nests which are estimated to consist of about 16 cells each. Adjacent oocytes within a nest are connected by intercellular bridges and develop synchronously. Each premeiotic interphase-leptotene oocyte has a round nucleus which contains one or two centrally located, spherical nucleoli. Electron-microscope radioautography showed that all nuclei in a cell nest incorporate thymidine synchronously during premeiotic S-phase. In zygotene oocytes, axial cores and synaptonemal complexes are observed in the nucleus and abut against the inner nuclear membrane in the region nearest the centre of the cell nest. The nucleolus is still more-or-less round in outline, but is asymmetrically positioned in the nucleus. It lies near the nuclear envelope on the side of the nucleus furthest away from the attachment of the chromosome ends, that is, nearest the outside of the cell nest. Each nucleolus is surrounded by a fibrillar ‘halo’ of nucleolus-associated chromatin into which a low level of thymidine incorporation occurs during zygotene. This is thought to represent the start of the major period of amplification of the ribosomal DNA. Pachytene is characterized by the presence of synaptonemal complexes in the nucleus. The nucleolus becomes very irregular in outline. The fibrillar area around it, which represents the extrachromosomal DNA, increases in size and thymidine is incorporated over the whole of this region. In late pachytene, many small fibrogranular bodies, the multiple nucleoli, are formed in it. The members of a cell nest become separated from one another at this time and begin to develop asynchronously. In diplotene, synaptonemal complexes are no longer observed in the nucleus. The most prominent structures in the nucleus are now the multiple nucleoli, which increase greatly in number in early diplotene. A large increase in cytoplasmic volume occurs and the oocyte grows in size.

Excision and replication of extrachromosomal DNA of pea (Pisum sativum)

1983 ◽  
Vol 3 (2) ◽  
pp. 172-181
Author(s):  
J Van't Hof ◽  
C A Bjerknes ◽  
N C Delihas
Keyword(s):  
Cell Cycle ◽  
Pisum Sativum ◽  
S Phase ◽  
Velocity Sedimentation ◽  
Extrachromosomal Dna ◽  
Chromosomal Dna ◽  
Root Tips ◽  
Dividing Cells ◽  
G2 Phase ◽  
Pea Roots

Experiments with cultured pea roots were conducted to determine (i) whether extrachromosomal DNA was produced by cells in the late S phase or in the G2 phase of the cell cycle, (ii) whether the maturation of nascent DNA replicated by these cells achieved chromosomal size, (iii) when extrachromosomal DNA was removed from the chromosomal duplex, and (iv) the replication of nascent chains by the extrachromosomal DNA after its release from the chromosomal duplex. Autoradiography and cytophotometry of cells of carbohydrate-starved root tips revealed that extrachromosomal DNA was produced by a small fraction of cells accumulated in the late S phase after they had replicated about 80% of their DNA. Velocity sedimentation of nascent chromosomal DNA in alkaline sucrose gradients indicated that the DNA of cells in the late S phase failed to achieve chromosomal size. After reaching sizes of 70 X 10(6) to 140 X 10(6) daltons, some of the nascent chromosomal molecules were broken, presumably releasing extrachromosomal DNA several hours later. Sedimentation of selectively extracted extrachromosomal DNA either from dividing cells or from those in the late S phase showed that it replicated two nascent chains, one of 3 X 10(6) daltons and another of 7 X 10(6) daltons. Larger molecules of extrachromosomal DNA were detectable after cells were labeled for 24 h. These two observations were compatible with the idea that the extrachromosomal DNA was first replicated as an integral part of the chromosomal duplex, was cut from the duplex, and then, once free of the chromosome, replicated two smaller chains of 3 X 10(6) and 7 X 10(6) daltons.

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