CONTRAST BETWEEN THE ENVIRONMENTAL pH DEPENDENCIES OF PROPHASING AND NUCLEAR MEMBRANE FORMATION IN INTERPHASE-METAPHASE CELLS

Obara, Yoshitaka; Yoshida, Hiroshi; Chai, Lee S.; Weinfeld, Herbert; Sandberg, Avery A.

doi:10.1083/jcb.58.3.608

Cited by 18 publications

(27 citation statements)

References 17 publications

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“…Some of these characteristics distinguish them from the mitotic factors (40). The pH dependency ofthese factors is also in agreement with the results of the early cell fusion experiments of Obara and co-workers (21)(22)(23), which suggested that high pH favored "telophasing" and low pH "prophasing" or premature chromosome condensation . Our own studies (Hittelman and Rao, unpublished data) show that the frequency of premature chromosome condensation induction is much higher if a low pH is maintained during the collection of mitotic cells and subsequent fusion procedures.…”

Section: Discussionsupporting

confidence: 88%

“…Obara and co-workers (21)(22)(23) have reported that in certain cases in these multinucleate cells 712 THE JOURNAL OF CELL BIOLOGY " VOLUME 97, 1983 containing higher ratio of interphase cells, a membrane is formed around the metaphase chromosomes. Because of its resemblance to the process occurring in normal telophase, this process has been termed "telophasing" (21)(22)(23) . They have also demonstrated that the larger the ratio of interphase nuclei to chromosomes in the fused cells the greater the possibility that "telophasing" would occur rather than prophasing .…”

Section: Inhibitors Of Mitotic Factorsmentioning

confidence: 99%

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Evidence for the presence of inhibitors of mitotic factors during G1 period in mammalian cells.

Adlakha¹,

Sahasrabuddhe²,

Wright³

et al. 1983

The Journal of Cell Biology

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Our earlier studies indicated that the mitotic factors, which induce germinal vesicle breakdown and chromosome condensation when injected into fully grown Xenopus oocytes, are preferentially associated with metaphase chromosomes and that they bind to chromatin as soon as they are synthesized during the G2 phase . In this study, we attempted to determine the fate of these factors as the cell completes mitosis and enters G, . Extracts from HeLa cells at different points during G,, S, and G2 periods were mixed with mitotic extracts in various proportions, incubated, and then injected into Xenopus oocytes to determine their maturationpromoting activity. The maturation-promoting activity of the mitotic extracts was neutralized by extracts of G, cells during all stages of G, but not by those of late S and G 2 phase cells . Extracts of quiescent (Go) human diploid fibroblasts exhibited very little inhibitory activity . However, UV irradiation of G o cells, which is known to cause decondensation of chromatin, significantly enhanced the inhibitory activity of extracts of these cells. These factors are termed inhibitors of mitotic factors (IMF) . They seem to be activated, rather than newly synthesized, as the cell enters telophase when chromosomes begin to decondense. The IMF are nondialyzable, nonhistone proteins with a molecular weight of >12,000 . Since mitotic factors are known to induce chromosome condensation, it is possible that IMF, which are antagonistic to mitotic factors, may serve the reverse function of the mitotic factors, i.e ., regulation of chromosome decondensation .Chromatin undergoes profound structural alterations during the cell cycle . During mitosis, it is supercoiled and condensed to form the mitotic chromosomes. Chromosome condensation is a critical event in the cell cycle that is necessary for the equal distribution of genetic material between the daughter cells. The phenomenon of premature chromosome condensation described by Johnson and Rao (13) has been very useful in visualizing the state of chromatin condensation during interphase. Using this technique, Rao and Hanks (30) and Hanks and Rao (9) have shown that the process of chromosome decondensation, initiated during the telophase of mitosis, continues throughout the G, period until the chromatin reaches its ultimate state ofdecondensation by the end of G,, when DNA synthesis is initiated .As for the factors involved in chromosome condensation, studies from this and other laboratories have demonstrated that when extracts from mitotic HeLa cells (39,40) or mitotic Chinese hamster ovary cells (19) are injected into Xenopus THE JOURNAL OF CELL BIOLOGY -VOLUME 97 DECEMBER 1983 1707-1713 C The Rockefeller University Press -0021-9525/83/12/1707/07 $1 .00 laevis oocytes, they exhibit maturation-promoting activity (MPA)' as evidenced by germinal vesicle breakdown (GVBD) and condensation of chromosomes. These studies also revealed that the mitotic factors are nonhistone proteins and accumulate slowly in the beginning of G2, increase rapid...

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Section: Discussionsupporting

confidence: 88%

Section: Inhibitors Of Mitotic Factorsmentioning

confidence: 99%

Evidence for the presence of inhibitors of mitotic factors during G1 period in mammalian cells.

Adlakha¹,

Sahasrabuddhe²,

Wright³

et al. 1983

The Journal of Cell Biology

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“…Cells in log phase were obtained about 15 16 h after subculture of the Don line and about 20 21 h in the case of HeLa cells. The cultures were treated with Colcemid, 0.08 ~tg/ml, for 5 h. After trypsinization for 3 min at 37°C (16) the cells were washed once with prewarmed pH-adjusted medium containing Colcemid and resuspended in fresh medium at 37°C at the same pH (16).…”

Section: Virus and Cellsmentioning

confidence: 99%

“…Procedures for cell fusion and slide preparation were essentially the same as those described in previous papers (4,16). Approximately l07 log phase cells or a mixture of metapbase and interphase cells (5 × l0 s cells of each) were suspended at 37°C in a total of 1.0 ml of pHadjusted medium containing 2,000 hemagglutinating units (HAU) of inactivated Sendal virus and 0.08 #g of Colcemid.…”

Section: Cell Fusion and Slide Preparationmentioning

confidence: 99%

“…The major event in the TLN formation appears to be a production of a new NE (4). The frequency of occurrence of either phenomenon in fused Don cells can be controlled by adjusting the environmental pH during and shortly after cell fusion: at relatively low pH the frequency of prophasing predominates, whereas at relatively high pH TLN formation predominates (16), Prophasing and TLN formation are mutually exclusive events, since I-M cells showing both phenomena are not observed (4,16).…”

Section: Introductionmentioning

confidence: 99%

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PROPHASING OF INTERPHASE NUCLEI AND INDUCTION OF NUCLEAR ENVELOPES AROUND METAPHASE CHROMOSOMES IN HELA AND CHINESE HAMSTER HOMO- AND HETEROKARYONS

Obara

Chai

Weinfeld

et al. 1974

The Journal of Cell Biology

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Fusing human HeLa metaphase cells with HeLa interphase cells resulted within 30 min in either of two phenomena in the resultant binucleate cell: either prophasing of the interphase nucleus or formation of a normal-appearing nuclear envelope around the metaphase chromosomes. The frequency of either occurrence was strongly dependent on environmental pH. At pH's of 6.6 8.0, prophasing predominated; at pH 8.5 nuclear envelope formation predominated. Additionally, the frequencies of the two events in multinucleate cells depended on the metaphase/interphase ratio. When the ratio was 0.33 nuclear envelope formation predominated; when it was 2.0 prophasing predominated. In their general features, the results with fused HeLa cells resembled those reported earlier with fused Chinese hamster Don cells. However, the results provided an indication that between pH 6.6 and 8.0 the HeLa metaphase cells possessed a much greater capacity than the Don metaphase cells to induce prophasing. Fusion of Don metaphase cells with HeLa interphase cells or of Don interphase cells with HeLa metaphase cells at pH 8.0 resulted in nuclear envelope formation or prophasing in each kind of heterokaryon. As in the homokaryons, the frequencies of the two events in the heterokaryons depended on the metaphase/interphase ratio. The statistics of prophasing and nuclear envelope formation in the homo-and heterokaryon populations were consistent with the notion that disruption or formation of the nuclear envelope depends on the balance attained between disruptive and formative processes.

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Disruption of the keratin filament network during epithelial cell division.

Lane¹,

S²,

Trejdosiewicz³

1982

The EMBO Journal

168

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The behaviour of keratin filaments during cell division was examined in a wide range of epithelial lines from several species. Almost half of them show keratin disruption as described previously: by immunofluorescence, filaments are replaced during mitosis by a ‘speckled’ pattern of discrete cytoplasmic dots. In the electron microscope these ‘speckles’ are seen as granules around the cell periphery, just below the actin cortical mesh, with no detectable 10 nm filament structure inside them and no keratin filament bundles in the rest of the cytoplasm. A time course of the filament reorganization was constructed from double immunofluorescence data; filaments are disrupted in prophase, and the filament network is intact again by cytokinesis. The phenomenon is restricted to cells rich in keratin filaments, such as keratinocytes; it is unrelated to the co‐existence of vimentin in many of these cells, and vimentin is generally maintained as filaments while the keratin is restructured. Some resistance to the effect may be conferred by an extended cycle time. Filament reorganization takes place within minutes, so that a reversible mechanism seems more likely than one involving de novo protein synthesis, at this metabolically quiet stage of the cell cycle.

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CONTRAST BETWEEN THE ENVIRONMENTAL pH DEPENDENCIES OF PROPHASING AND NUCLEAR MEMBRANE FORMATION IN INTERPHASE-METAPHASE CELLS

Cited by 18 publications

References 17 publications

Evidence for the presence of inhibitors of mitotic factors during G1 period in mammalian cells.

Evidence for the presence of inhibitors of mitotic factors during G1 period in mammalian cells.

PROPHASING OF INTERPHASE NUCLEI AND INDUCTION OF NUCLEAR ENVELOPES AROUND METAPHASE CHROMOSOMES IN HELA AND CHINESE HAMSTER HOMO- AND HETEROKARYONS

Disruption of the keratin filament network during epithelial cell division.

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