Camptothecin is a specific topoisomerase I poison and highly cytotoxic to eukaryotic cells. In the present study, we show, using pulse field gel electrophoresis assay, that camptothecin induces DNA double strand breaks (DSBs) specifically in newly replicated DNA. these replication associated DSBs dose-dependent manner. At levels of drug which are toxic cell, long-lived, still measurable 24 hr after treatment. Both induced cytotoxicity prevented by co-exposure with aphidicolin--a result...

DNA topoisomerase II (EC 5.99.1.3) is necessary for chromosome condensation and disjunction in yeast but not other functions. In mammalian cells, it has been reported to be progression toward mitosis transit through mitosis. We have found, on the contrary, that specific inhibition of (but I) interferes with mitotic progression. Metaphase prolonged, anaphase separation chromatids completely inhibited, cells given high concentrations inhibitors; nevertheless these attempt cleavage, sometimes...

Abstract The phenomenon of premature chromosome condensation (PCC) is induced in unstimulated horse lymphocytes, bovine spermatozoa, Chinese hamster ovary cells, embryonic chick fibroblasts and erythrocytes, Xenopus kidney mosquito cells by fusing each these cell types with HeLa blocked mitosis. Thus it becomes possible to visualize chromosomes even from non‐multiplying heterologous species, such as, erythrocytes spermatozoa.

Sendai virus-mediated fusion between mitotic and interphase mammalian cells causes the rapid condensation of chromosomes into distinct structures, a process termed premature chromosome condensation. This phenomenon has been used to assess immediate action x-rays ultraviolet light on HeLa irradiated in G1 phase life cycle. X-irradiation produces fragmented chromosomes; but even most finely chopped fragments retain condensed morphology characteristic unirradiated cells. For doses up about 1800...

Cell fusion experiments have been carried out with Chinese hamster cell mutants different nutritional growth requirements. Conditions devised in which approximately 1 to 2 percent of the population remaining after are fused, hybrid cells. The all-or-none nature genetic markers employed and extremely low reversion rates insure that no contamination parental forms occurs. Hybrids between glycine- hypoxanthine-requiring prototrophic, indicates both mutations recessive. a glycine-deficient...

Cell-matrix adhesion is essential for building animals, promoting tissue cohesion, and enabling cells to migrate resist mechanical force. Talin an intracellular protein that critical linking integrin extracellular-matrix receptors the actin cytoskeleton. A key question raised by structure-function studies whether talin, which all integrin-mediated adhesion, acts in same way every context. We show distinct combinations of talin domains are required each three different functions during...

ABSTRACT Yeast temperature-sensitive mutants of DNA topoisomerase II are incapable chromosome condensation and anaphase chromatid segregation. In mammalian cells, inhibitors such as etoposide (VP-16-123) have similar effects. Unfortunately, conclusions drawn from work with cells been limited by the fact that standard also generate strand breaks, which when produced other agents (e.g. ionizing radiation) known to affect progression into through mitosis. Here we show anti-tumour agent...

In addition to inhibiting replicative DNA synthesis in HeLa cells, novobiocin has a severe effect on the cellular response UV irradiation, reducing number of breaks made pre-existing by excision repair process. The inhibition is reflected enhanced UV-killing these cells. Rejoining after X irradiation not impaired novobiocin. recognition and removal damage may require unwinding gyrase, which - bacteria target for

ADAMTS-1 is an extracellular protease with critical roles in organogenesis and angiogenesis. Here we demonstrate a functional convergence of the transmembrane heparan sulfate proteoglycan syndecan-4 influencing adhesion, migration Knockdown endothelial cells resulted parallel reduction cell surface syndecan-4, attributable to increased matrix metalloproteinase-9 (MMP9) activity. either or cellular responses vascular growth factor A isoform VEGFA164, ex vivo aortic ring microvessel sprouting....

We have examined the use of pulsed-field gel electrophoresis (PFGE) to measure DNA double-strand breaks induced in CHO cells by ionizing radiation. The PFGE assay provides a simple method for measurement doses as low 3-4 Gy radiation, and appears applicable damage produced any agent producing breaks. conditions transverse alternating field determined both sensitivity ability resolve fragments with different sizes. For example, 0.8% agarose 1-min pulse time at 250 V 18 h electrophoresis,...

Metaphase chromatids are believed to consist of loops chromatin anchored a central scaffold, which major component is the decatenatory enzyme DNA topoisomerase II. Silver impregnation selectively stains an axial element metaphase and anaphase chromatids; but we find that in earlier stages mitosis, silver staining reveals initially single, folded midline structure, separates at prometaphase form two chromatid axes. Inhibition II prevents this separation, also contraction occurs when arrested....

The CHO mutant UV61 was previously assigned to complementation group 6 of UV-sensitive rodent cell mutants. is less sensitive killing by UV radiation than mutants such as UV5, which highly defective in the incision process that acts on UV-induced lesions. D37 for survival ∼4 J/m2 UV61, compared with 10 parental AA8 line and ∼2 UV5. Similarly, mutation induction at hprt aprt loci shows an intermediate response UV61. In a post-replication recovery assay, kinetics maturation pulse-labelled...

Novobiocin inhibits DNA topoisomerases. It also excision repair of photodamage, blocking both synthesis and the earlier step incision at u.v. damage sites (as measured by accumulation strand breaks in u.v.-irradiated interphase cells treated with inhibitors such as hydroxyurea or cytosine arabinoside). has been supposed, therefore, that novobiocin affects a putative topoisomerase prior to incision. But we find marked dose- time-dependent effect on mitochondria: exposed novobiocin,...

ABSTRACT Fusion between mitotic and interphase cells results in the premature condensation of chromosomes into a morphology related to position cell cycle at time fusion. These prematurely condensed (PCC) have been used conjunction with u.v. irradiation examine chromosome HeLa cells. The following observations made: (1) There is progressive decondensation during G1 which accentuated by irradiation: (2) become more resistant u.v.-induced mitosis. (3) close correlation degree amount...

We have measured repair DNA synthesis in UV-irradiated normal human fibroblasts, grown to a defined state of quiescence order avoid the problem discriminating from replicative synthesis. assessed effects various inhibitors on repair. Inhibition by hydroxyures, 1-β-D-arabinofuranosylcytosine and aphidicolin is associated with ability accumulate breaks due enzymic incision at damage sites; inhibition novobiocin accord its known block incision.

ABSTRACT When chick erythrocyte nuclei are introduced into the cytoplasm of HeLa cells they resume synthesis DNA. The reactivated synthesize DNA in a highly co-ordinated manner and essentially synchrony with nuclei. Asynchronous is rare. respond to signals which regulate same way as nuclei; do not, for at least 2 days after cell fusion, interfere any