Differential cleavate of <i>physarum</i> DNA from distinct points of S phase by restriction enzyme Eco RI

Fouquet, H.; Sauer, Helmut W.

doi:10.1016/0014-5793(76)81045-9

Cited by 3 publications

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References 13 publications

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“…In addition, Fouquet and Sauer (10) have shown that repetitive DNA of Physarum is synthesized during late S phase. At the level of specific genes, Pierron et al (11) have recently found that the four actin loci are replicated in an invariant temporal order over a period of at least 400 generation times.…”

Section: Introductionmentioning

confidence: 99%

Replication timing of the H4 histone genes in Physarum polycephalum.

Jalouzot¹,

Toublan²,

Wilhelm³

et al. 1985

Proc. Natl. Acad. Sci. U.S.A.

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The time of replication of the two H4 histone genes (H41 and H42) was determined during the naturally synchronous mitotic cycle of Physarum polycephalum. 5-Bromo-2'-deoxyuridine labeling and density gradient centrifugation was used to isolate newly synthesized DNA from defined periods of S phase. The DNA was analyzed by Southern hybridization with a cloned probe containing one of the H4 histone genes ofPhysarum. The results indicate that the two H4 histone genes are replicated in the first 30 min of S phase but not exactly at the same time. H41 is replicated during the frt 10 min of S phase, when only 15% of the genome is duplicated, whereas H42 replicates between 20 and 30 min after the onset of S phase. The possible relationship between the periodic expression of the genes and the timing of their replication is discussed.In eukaryotes, as in prokaryotes, the replication of specific DNA sequences follows a distinct temporal order (1, 2). DNA replicated in one period of the S phase is replicated in the same temporal interval of the next S phase. In early experiments autoradiography and cytology was used to demonstrate that the chronological order of replication of specific DNA segments is invariant from one cell generation to the next (3).In mammalian cells, multiple copy sequences have been found to replicate mainly late in S phase, whereas families of middle-repetitive sequences replicate either early or late (for references see ref. 4). "Housekeeping" or active tissuespecific genes are generally replicated early. Furst et al. (5) and Epner et al. (6) have, for example, demonstrated that the replication of globin genes in mouse erythroleukemia cells is predominantly restricted to the first third of S phase. In the same manner, studies by Braunstein et al. (7) have shown that the replication of the immunoglobulin heavy chain constant region gene segments CQ, Cy, and C, is restricted to the first half of S and follows the linear order in which they are arranged in the genome. Recently Calza et al. (8) have presented evidence that certain low-copy-number genes can be replicated late and have suggested that the gene's position in the chromosome is important in determining the time during S at which it is replicated. All the results presented on the timing of gene replication support the idea that earlyreplicating genes are capable of expression, and Goldman et al. (4) suggest that the switching of specific genes from an early to a late replication region reflects the commitment of that gene to quiescence.The sustained synchrony over several successive nuclear division cycles in the syncytial plasmodia phase of the myxomycete Physarum polycephalum was exploited by Braun et al. (9) to demonstrate that chromosomal DNA is replicated in a defined temporal sequence. In addition, Fouquet and Sauer (10) have shown that repetitive DNA of Physarum is synthesized during late S phase. At the level of specific genes, Pierron et al. (11) have recently found that the four actin loci are replicated in an invariant tempo...

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Section: Introductionmentioning

confidence: 99%

Replication timing of the H4 histone genes in Physarum polycephalum.

Jalouzot¹,

Toublan²,

Wilhelm³

et al. 1985

Proc. Natl. Acad. Sci. U.S.A.

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Regulation of Gene Expression in the Cell Cycle of Physarum

Sauer¹

1978

Cell Cycle Regulation

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Two‐dimensional gel analysis of repetitive nuclear DNA sequences in the genome of Physarum polycephalum

Meyer

Hildebrandt

1986

European Journal of Biochemistry

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1. The composition of repetitive sequences in restriction patterns of nuclear DNA of Physarum polycephalum was determined by high-resolution gel analysis.2. Three types of repeated DNA fragments in the size range of (0.2-2) x lo3 base pairs could be identified as discrete spots on the gels and distinguished by their abundance and above-average base composition of either guanine and cytosine (G + C) or adenine and thymidine (A +T). 3.On comparing the DNA composition from exponentially growing plasmodia with that of starved plasmodia, which have become competent to sporulate and have lost 80% of their nuclei, no change was detected among the (A + T)-rich repeat fractions, whereas several of the (G + C)-rich fractions revealed fewer copies in the DNA prepared from starved cells.4. As shown by hybridization under saturating conditions, the reduction of several (G + C)-rich repeated sequences in the restricted nuclear DNA in sporulation-competent cells can be explained by a 64% elimination of the extrachromosomal nucleolar ribosomal DNA sequences.The DNA content in the slime mold Physarum polycephalum is extraordinarily variable. Different strains contain different amounts of nuclear DNA and there exist constitutively mixoploid strains, like M3cIV with two kinds of nuclei differing by 18% in their DNA content [l]. Furthermore, the nuclear DNA content has been shown to decrease as a function of aging by about 20% in M3cVII [2].It is not known whether the variable DNA contents in Physarurn reflect overreplication and underreplication of genomic segments in response to physiological conditions, or the establishment of a germline during sporulation.We assume that expansion and diminution of the genome of Physarurn should affect the composition of repetitive sequences. These are non-randomly distributed over the genome in Physarum During starvation, surface plasmodia (macroplasmodia) of Physarum degrade a large part ( x 80%) of their nuclei as well as RNA, proteins and glycogen, reaching a state of competence to sporulate after 3 -4 days. Sporulation can then be induced by illumination, which initates the irreversible sporulation pathway. During this differentiation process most of the remaining 20% of the nuclei are packed up into spores, where they undergo meiosis [7].We have compared the restriction patterns of the nuclear DNA from plasmodia growing exponentially in liquid culture (microplasmodia) and from starved sporulation-competent plasmodia in order to identify a possible germline-specific composition of repetitive sequences. The restriction patterns were analyzed two-dimensionally, which increases the resolution and simultaneously gives rapid information about the relative G + C or A + T content of the individual fragments The only repetitive sequences for which we could demonstrate a change in frequency are the extrachromosomal nucleolar sequences, which were reduced to about 36% of the control value in the plasmodia competent for sporulation.The Physarum nucleolar DNA molecules are extrachromosomal, autonomousl...

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Differential cleavate of physarum DNA from distinct points of S phase by restriction enzyme Eco RI

Cited by 3 publications

References 13 publications

Replication timing of the H4 histone genes in Physarum polycephalum.

Replication timing of the H4 histone genes in Physarum polycephalum.

Regulation of Gene Expression in the Cell Cycle of Physarum

Two‐dimensional gel analysis of repetitive nuclear DNA sequences in the genome of Physarum polycephalum

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