Chromosome replication in early development of Xenopus laevis

Development ◽  
1985 ◽  
Vol 89 (Supplement) ◽  
pp. 285-296
Author(s):  
R. A. Laskey
Keyword(s):  
Dna Replication ◽  
Xenopus Laevis ◽  
Early Development ◽  
Chromosome Replication ◽  
Chromatin Assembly

Eggs of Xenopus laevis contain exceptionally large amounts of materials involved in chromosome replication. This maternal stockpile allows an embryo to produce about 80 000 cells in less than 24 h. The adaptations which achieve this involve the mechanisms of both DNA replication and chromatin assembly.

scholarly journals Histones synthesized for use in early development of Xenopus laevis are stored as a complex with antigenic properties similar to those of the octamer core of nucleosomes.

1982 ◽  
Vol 92 (3) ◽  
pp. 871-876 ◽  
Author(s):  
W C Earnshaw ◽  
O P Rekvig ◽  
K Hannestad
Keyword(s):  
Xenopus Laevis ◽  
Early Development ◽  
Lupus Erythematosus ◽  
Protein A ◽  
Chromatin Assembly ◽  
Soluble Complex ◽  
Antigenic Properties ◽  
Antibody Complex ◽  
Nuclear Synthesis ◽  
Assembly Activity

Serum of patients with systemic lupus erythematosus (SLE) contains crossreacting autoantibodies which recognize histones in nucleosomes or when they are induced to form octamers in solution in the presence of 2 M NaCl, but not when they are dissociated free in solution at physiological ionic strength. We have found that histones stored in eggs of Xenopus laevis for use in rapid nuclear synthesis during early development react with this antibody. This reaction has been observed by radioimmunoassay, inhibition of chromatin assembly by the extracts in the presence of antibody, and, in a preliminary result, by identification of a histone-antibody complex bound to protein A-sepharose. Further evidence that the extract antigen corresponds to the stored histone pool comes from sedimentation and charge fractionation experiments where the chromatin assembly activity and antigen (measured by radioimmunoassay) were found to cofractionate. BEcause the extract histones are not bound to DNA, our results suggest that they are stored as a soluble complex in a conformation similar or identical to the octameric core of the nucleosome. Our data suggest that the histones in this complex are bound to an anionic factor or factors which presumably replaces the DNA in shielding the positive charges on the histones.

scholarly journals Dynamics of the Genome during Early Xenopus laevis Development: Karyomeres As Independent Units of Replication

1998 ◽  
Vol 142 (5) ◽  
pp. 1159-1166 ◽  
Author(s):  
Jean-Marc Lemaitre ◽  
Gérard Géraud ◽  
Marcel Méchali
Keyword(s):  
Dna Replication ◽  
Xenopus Laevis ◽  
Early Development ◽  
Mitotic Spindle ◽  
Genomic Organization ◽  
Blastula Stage ◽  
M Phase ◽  
Initiation Of Dna Replication ◽  
Segregation Of Chromosomes

During Xenopus laevis early development, the genome is replicated in less than 15 min every 30 min. We show that during this period, DNA replication proceeds in an atypical manner. Chromosomes become surrounded by a nuclear membrane lamina forming micronuclei or karyomeres. This genomic organization permits that prereplication centers gather on condensed chromosomes during anaphase and that DNA replication initiates autonomously in karyomeres at early telophase before nuclear reconstruction and mitosis completion. The formation of karyomeres is not dependent on DNA replication but requires mitotic spindle formation and the normal segregation of chromosomes. Thus, during early development, chromosomes behave as structurally and functionally independent units. The formation of a nuclear envelope around each chromosome provides an in vivo validation of its role in regulating initiation of DNA replication, enabling the rate of replication to accelerate and S phase to overlap M phase without illegitimate reinitiation. The abrupt disappearance of this atypical organization within one cell cycle after thirteen divisions defines a novel developmental transition at the blastula stage, which may affect both the replication and the transcription programs of development.

Nuclear distribution of PCNA during embryonic development in Xenopus laevis: a reinvestigation of early cell cycles

1992 ◽  
Vol 102 (1) ◽  
pp. 63-69 ◽  
Author(s):  
M. Leibovici ◽  
G. Monod ◽  
J. Geraudie ◽  
R. Bravo ◽  
M. Mechali
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Xenopus Laevis ◽  
Early Development ◽  
Nuclear Periphery ◽  
S Phase ◽  
Nuclear Antigen ◽  
Midblastula Transition ◽  
Cell Cycles ◽  
Cyclical Pattern

The immunocytological distribution of the proliferating cell nuclear antigen (PCNA), a protein involved in DNA replication, has been examined during the early development of Xenopus laevis. The protein is uniformly detected in nuclei during early stages up to the neurula stage. PCNA is detected by its distinctive cyclical pattern during early development, remaining detectable only during the period of S phase of each cell cycle. Immunological detection of PCNA is therefore a useful and specific non-isotopic marker of S-phase cells in the embryo. PCNA associates with typical karyomeric structures, suggesting that DNA replication starts before the nuclear compartment is entirely formed. At the midblastula transition, a new pattern of PCNA staining becomes apparent. First, a new type of PCNA staining is detected at the nuclear periphery. Second, mitotic clusters with different PCNA distributions suggest that the onset of desynchronization of the cell cycle at this stage is not random.

Early development of dorsal column-medial lemniscal projections in the clawed toad, Xenopus laevis

1993 ◽  
Vol 74 (2) ◽  
pp. 291-294 ◽  
Author(s):  
A. Múñoz ◽  
R. de Boer-Van Huizen ◽  
I. Bergervoet-Vernooy ◽  
H.J. ten Donkelaar
Keyword(s):  
Xenopus Laevis ◽  
Early Development ◽  
Dorsal Column

scholarly journals Essential Role of Chromatin Assembly Factor-1–mediated Rapid Nucleosome Assembly for DNA Replication and Cell Division in Vertebrate Cells

2007 ◽  
Vol 18 (1) ◽  
pp. 129-141 ◽  
Author(s):  
Yasunari Takami ◽  
Tatsuya Ono ◽  
Tatsuo Fukagawa ◽  
Kei-ichi Shibahara ◽  
Tatsuo Nakayama
Keyword(s):  
Dna Replication ◽  
Essential Role ◽  
Chromatin Assembly ◽  
Nuclear Antigen ◽  
Nucleosome Assembly ◽  
Chromatin Assembly Factor ◽  
Assembly Factor

Chromatin assembly factor-1 (CAF-1), a complex consisting of p150, p60, and p48 subunits, is highly conserved from yeast to humans and facilitates nucleosome assembly of newly replicated DNA in vitro. To investigate roles of CAF-1 in vertebrates, we generated two conditional DT40 mutants, respectively, devoid of CAF-1p150 and p60. Depletion of each of these CAF-1 subunits led to delayed S-phase progression concomitant with slow DNA synthesis, followed by accumulation in late S/G2 phase and aberrant mitosis associated with extra centrosomes, and then the final consequence was cell death. We demonstrated that CAF-1 is necessary for rapid nucleosome formation during DNA replication in vivo as well as in vitro. Loss of CAF-1 was not associated with the apparent induction of phosphorylations of S-checkpoint kinases Chk1 and Chk2. To elucidate the precise role of domain(s) in CAF-1p150, functional dissection analyses including rescue assays were preformed. Results showed that the binding abilities of CAF-1p150 with CAF-1p60 and DNA polymerase sliding clamp proliferating cell nuclear antigen (PCNA) but not with heterochromatin protein HP1-γ are required for cell viability. These observations highlighted the essential role of CAF-1–dependent nucleosome assembly in DNA replication and cell proliferation through its interaction with PCNA.

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