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PubMed1990

Distribution of phorbol ester TPA-induced structural chromosomal aberrations in HeLa cells.

In order to gain further insight into the mechanism of clastogenic action of the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA), the localization and distribution of structural chromosomal aberrations on HeLa chromosomes was investigated. We have shown by the G-banding technique that TPA-induced chromosomal aberrations in HeLa cells have practically the same distribution as that occurring spontaneously in control cultures. About two-thirds of the breakpoints are located in areas of known fragile sites; about one-third is located in regions near known oncogenes. The tumor promoter TPA thus appears to enhance pre-existing mechanisms of an 'endogeneous' clastogenesis.

Chromosome Aberrations↗
PubMed1999

A family of dispersed repeats in the genome of Vicia faba: structure, chromosomal organization, redundancy modulation, and evolution.

A family of repeated DNA sequences of about 1200 bp in length and bordered by well-conserved, 18 bp inverted repeats (VfB family) was found in the nuclear genome of Vicia faba. The structure, chromosomal organization, redundancy modulation and evolution of these sequences were investigated. They are enriched in A+T base pairs (about 40% G+C) and lack any obvious internally repeated motif. A 64%-73% nucleotide sequence identity was found when pairwise comparisons between VfB sequences were carried out (average 69%). Direct repeats were not found to flank the inverted repeats that border these DNA sequences. The results obtained by hybridizing VfB repeats to Southern blots of V. faba genomic DNA digested with EcoRI indicated that these DNA elements are interspersed in the genome. The appearance of bands in these Southern blots and comparison of the structure of the sequences that flank different VfB elements showed that these repeats might be part of other, longer repeated DNA sequences. A high degree of dispersion throughout the genome was confirmed by cytological hybridization, which showed VfB sequences to be scattered along the length of all chromosomes and to be absent or rare only at heterochromatic chromosomal regions. These sequences contribute to intraspecific alterations of genomic size. Indeed, dot-blot hybridizations proved that their redundancy, which is positively correlated with the overall amount of nuclear DNA in each accession, varies between V. faba land races (27x10(3)-230x10(3) copies per 1C DNA). Southern blot hybridization of VfB repeats to restriction endonuclease-digested genomic DNAs of V. faba, V. narbonensis, V. sativa, Phaseolus coccineus, Populus deltoides, and Triticum durum revealed nucleotide sequence homology of these DNA elements, whatever the stringency conditions, only to the DNAs of Vicia species, and to a reduced extent to the DNAs of V. narbonensis and V. sativa compared with that of V. faba. It is concluded that VfB repeats might be descended from mobile DNA elements and contribute to change genomic size and organization during evolution.

Base Composition↗
PubMed1988

Frequency and distribution of mitomycin C-induced structural chromosome aberrations in lymphocytes from non-Hodgkin lymphoma patients.

Lymphocytes from 15 untreated patients with non-Hodgkin lymphoma (NHL) and 15 controls were exposed to 0.08 micrograms/ml mitomycin C, and the frequency and distribution of structural chromosome aberrations (chromatid and chromosome gaps, breaks, and exchanges) were analyzed in 100 mitoses per subject. The mean frequencies of aberrant cells, and gap, break, and gap + break events were 8.7, 0.9, 9.7, and 10.6 in the NHL group and 11.6, 1.1, 12.7, and 13.8 in the control group. None of the differences between the two groups was significant (P greater than 0.05). The distribution of breakpoints was nonrandom (P less than 0.001) in both groups, with a particularly marked excess of breaks in 9q11. The other breakage-prone bands were 1q11 and 1q21 in the NHL group and 1p11, 1q11, 2q31, and 16q11 in the control group. None of these hot spots coincided with any of the 60 bands known to be involved in primary chromosome abnormalities in NHL.

Adult↗
PubMed2001

Acquisition of secondary structural chromosomal changes in pediatric ewing sarcoma is a probable prognostic factor for tumor response and clinical outcome.

BACKGROUND: The Ewing sarcoma (ES) group of tumors commonly have the t(11;22)(q24;q12) or other rearrangements involving 22q12. In addition to these consistent aberrations, both numeric and structural aberrations have been reported: namely gains of chromosomes 8 and 12, the unbalanced translocation t(1;16), and deletions at the short arm of chromosome 1. METHODS: To evaluate the frequency and to study the prognostic implications of some of these aberrations in children, the authors performed a pilot study of 26 ES pediatric patients by classic cytogenetics and/or interphase fluorescence in situ hybridization (FISH) and compared these data with clinical parameters. RESULTS: Gains of chromosomes 8 and 12 were detected, by interphase FISH, in 48% (10 of 21) and 38% (6 of 16) of the tumors, respectively, and this was not significant with respect to treatment response. Statistical analysis revealed that the presence of additional secondary structural chromosomal aberrations was associated with an unfavorable outcome (P = 0.0034 as an independent prognostic value as an unfavorable marker). Presence of metastasis at diagnosis also was found to be associated with poor outcome (P = 0.0131). Spectral karyotyping analysis was shown to facilitate the detection of more complex structural chromosomal aberrations in a representative ES tumor. CONCLUSIONS: It is important to determine whether additional structural chromosomal aberrations are present in ES tumors because it appears that a more complex karyotype with multiple chromosomal aberrations is associated with poor outcome in ES.

Adolescent↗
PubMed1995

Nuclear organization: uniting replication foci, chromatin domains and chromosome structure.

In higher eukaryotes, 'replication factories' coordinate DNA synthesis within local clusters of chromatin domains. Recent experiments (1, 2) have confirmed the complexity of these clusters and established that the organization of sites labelled during S phase persists throughout the cell cycle. This implies that domain clusters are critical elements of an hierarchy that is fundamental to both nuclear and chromosome structure.

Animals↗
PubMed1996

Difference in types of radiation-induced structural chromosome aberrations and their incidences between Chinese and Syrian hamster spermatozoa.

The effects of ionizing radiations on sperm chromosomes were studied in the Chinese hamster (Crisetulus griseus) and the Syrian (golden) hamster (Mesocrisetus auratus). Testes of mature male Chinese hamsters (CH) were irradiated with X-rays (0.91, 1.82 and 3.63 Gy) and gamma-rays (1.10, 2.15, 2.95 and 4.01 Gy) at a single acute dosage, whereas the irradiation was done with lower doses of X-rays (0.45, 0.91 and 1.82 Gy) and gamma-rays (0.49, 0.99 and 1.98 Gy) in mature male Syrian hamsters (SH), taking the higher radiosensitivity of this species into consideration. They were mated with normal females within 6 days of exposure. Sperm-derived chromosomes were analyzed in 1125 and 1966 fertilized ova of the CH and the SH, respectively. In both species, there was no great difference in the induction of structural chromosome aberrations between X-irradiated and gamma-irradiated spermatozoa. Chromosome-type aberrations were predominantly induced. The incidence of breakage-type aberrations increased linearly, and that of exchange-type aberrations linear-quadratically with increase of dosage. A species-specific difference in chromosomal radiosensitivity of spermatozoa was clear. In spite of the same radiation dosage, the incidence of chromosomally abnormal spermatozoa in the SH was about twice as high as that in the CH (e.g. 27.0% vs. 14.7% at 0.91 Gy of X-rays). The incidences of breakage-type aberrations (69-89%) were far higher than those of exchange-type aberrations (11-31%) in the SH, while the disparity of the two incidences was much smaller in the CH (46-65% vs. 35-54%). Exchange-type aberrations consisted of both chromosome-type and chromatid-type in the SH, while almost all of them were of the chromosome-type in the CH. These results suggest that the DNA-repairing capacity of oocytes is much higher in the CH than in the SH. Moreover, it seems likely that radiation-induced sperm DNA damage is repaired with both pre-replication repair (excision repair) and post-replication repair systems in SH oocytes, whereas the excision repair system operate most exclusively in CH oocytes.

Analysis of Variance↗
PubMed1998

Replicon clusters are stable units of chromosome structure: evidence that nuclear organization contributes to the efficient activation and propagation of S phase in human cells.

In proliferating cells, DNA synthesis must be performed with extreme precision. We show that groups of replicons, labeled together as replicon clusters, form stable units of chromosome structure. HeLa cells were labeled with 5-bromodeoxyuridine (BrdU) at different times of S phase. At the onset of S phase, clusters of replicons were activated in each of approximately 750 replication sites. The majority of these replication "foci" were shown to be individual replicon clusters that remained together, as stable cohorts, throughout the following 15 cell cycles. In individual cells, the same replication foci were labeled with BrdU and 5-iododeoxyuridine at the beginning of different cell cycles. In DNA fibers, 95% of replicons in replicon clusters that were labeled at the beginning of one S phase were also labeled at the beginning of the next. This shows that a subset of origins are activated both reliably and efficiently in different cycles. The majority of replication forks activated at the onset of S phase terminated 45-60 min later. During this interval, secondary replicon clusters became active. However, while the activation of early replicons is synchronized at the onset of S phase, different secondary clusters were activated at different times. Nevertheless, replication foci pulse labeled during any short interval of S phase were stable for many cell cycles. We propose that the coordinated replication of related groups of replicons, that form stable replicon clusters, contributes to the efficient activation and propagation of S phase in mammalian cells.

Antimetabolites↗
PubMed1975

[Cytogenetic studies of preinvasive lesions and invasive carcinomas of the cervix uteri. II. Structural chromosome abnormalities. Karyotype deviations (author's transl)].

An analysis of karyotypes was possible in 17 preinvasive lesions (3 dysplasias, 14 carcinomas in situ) and 15 invasive lesions of the cervix uteri (3 carcinomas in situ with microinvasion, 12 invasive squamos carcinomas - at least clinical stage I b). With regard to the structural chromosome abnormalities or karyotype deviations in this study the preinvasive lesions analysed could not be differentiated in principle as a group from the invasive lesions. The question of whether the dysplasia group would be different on further investigation with more cases and could be differentiated like the numerical deviations cannot yet be answered, because of the small numbers, only preinvasive lesions and invasive lesions could be studied comparatively as groups.

Adult↗
PubMed2001

Structure, chromosomal localization, and expression of the gene for mouse ecto-mono(ADP-ribosyl)transferase ART5.

Mono(ADP-ribosyl)transferases regulate the function of target proteins by attaching ADP-ribose to specific amino acid residues in their target proteins. The purpose of this study was to determine the structure, chromosomal localization, and expression profile of the gene for mouse ecto-ADP-ribosyltransferase ART5. Southern blot analyses indicate that Art5 is a single copy gene which maps to mouse chromosome 7 at offset 49.6 cM in close proximity to the Art1, Art2a and Art2b genes. Northern blot and RT-PCR analyses demonstrate prominent expression of Art5 in testis, and lower levels in cardiac and skeletal muscle. Sequence analyses reveal that the Art5 gene encompasses six exons spanning 8 kb of genomic DNA. The 5' end of the Art5 gene overlaps with that of the Art1 gene. A single long exon encodes the predicted ART5 catalytic domain. Separate exons encode the N-terminal leader peptide and a hydrophilic C-terminal extension. Sequencing of RT-PCR products and ESTs identified six splice variants. The deduced amino acid sequence of ART5 shows 87% sequence identity to its orthologue from the human, and 37 and 32% identity to its murine paralogues ART1 and ART2. Unlike ART1 and ART2, ART5 lacks a glycosylphosphatidylinositol-anchor signal sequence and is predicted to be a secretory enzyme. This prediction was confirmed by transfecting an Art5 cDNA expression construct into Sf9 insect cells. The secreted epitope-tagged ART5 protein resembled rat ART2 in exhibiting potent NAD-glycohydrolase activity. This study provides important experimental tools to further elucidate the function of ART5.

ADP Ribose Transferases↗
PubMed1996

Comparison of spontaneous structural chromosome aberration frequency in 48 h-cultured human lymphocytes mitotically arrested by different colcemid treatments.

Alterations in mitotic index and cell cycle kinetics are reported to be dependent on both the culture conditions and the ability of the lymphocytes of each individual to respond to phytohaemagglutinin stimulus. Thus, the frequency of structural chromosome aberrations (CA) could prove to be affected to some degree by these parameters. CA frequency and cell proliferation index (PI) were assessed in a group of healthy subjects after adding colcemid to cultured lymphocytes 3 h (standard) and 22 h (modified) before cell fixation at 48 h. All control cultures treated with colcemid for 22 h consisted exclusively of first metaphases, whereas the proportion of second-division lymphocytes in standard cultures (3 h colcemid) ranged from 4% to 49%. In addition, CA frequencies with and without gaps were always elevated in modified cultures as compared to the standard ones, and the difference between CA percentages obtained with the two methods was found to be significantly related with increasing PI values.

Adult↗
PubMed1994

Characterization of the genomic structure, chromosomal location, promoter, and development expression of the alpha-globin transcription factor CP2.

We recently cloned murine and human cDNAs that encode CP2, a cellular transcription factor that interacts with the alpha-globin promoter as well as with additional cellular and viral promoter elements. We have now characterized the genomic structure, chromosome location, promoter, and expression pattern of the factor. Genes for the murine and human mRNAs contained 16 and 15 exons, respectively. Both genes spanned approximately 30 kilobases of chromosomal DNA, and among coding exons, all exon/intron boundaries were conserved. The human gene for CP2 was found to reside on chromosome 12 while the murine gene mapped to the distal end of chromosome 15, near Gdc-1, Wnt-1, and Rarg, a region syntenic with human chromosome 12. The murine and human promoters initiated mRNAs at multiple start sites in a conserved region that spanned more than 450 nucleotides. Lastly, a study of the pattern of CP2 gene expression showed that the factor was expressed in all adult and fetal murine tissues examined from at least day 9.5 of development.

Amino Acid Sequence↗
PubMed2003

[Detection of the frequencies of numerical and structural chromosome aberrations in sperm of benzene series-exposed workers by multi-color fluorescence in situ hybridization].

To study the frequencies of numerical and structural aberrations for chromosome in sperm of benzene exposed workers, the multi-color FISH was used. Four DNA probes(one for chromosome 1 centromere and one for 1 p terminal, and two for chromosome 18 centromere) were hybridized with interphase sperms, and the frequencies of numerical aberrations for chromosome 1, 18 and structural aberrations of chromosome 1 were detected simultaneously. The time weighted average concentration (TWA) of benzene in workplace (42.29 mg/m3) was higher than that of our national maximum allowable concentration (6 mg/m3). The geometric concentration of urinary trans, trans-muconic acid(tt-MA) in exposed group was significantly higher than that of control group. A total of 144,282 sperm of 15 benzene-exposed workers and 135,937 sperm in 14 controls were scored. The frequency of hybridization efficiency was 99.85%. The mean frequencies of disomic sperms for chromosome 1 and 18 in exposed group(0.088% +/- 0.041%, and 0.087% +/- 0.049%, respectively) were statistically increased over that of the control group(0.045% +/- 0.024%, and 0.035% +/- 0.028%), and the mean frequencies of nullisomic sperms for chromosome 1 and 18(0.11% +/- 0.059%, 0.075% +/- 0.035%) in exposed group were statistically increased over that of control group too (0.048% +/- 0.018%; 0.045% +/- 0.024%). The frequencies of diploidy sperm were no difference in both exposed and control groups. The mean frequencies of terminal duplication and terminal deletion for chromosome 1 p(0.16% +/- 0.037%; 0.14% +/- 0.053%, respectively) were significantly increased over that of control group(0.082% +/- 0.023%; 0.069% +/- 0.028%, respectively). The mean frequencies of centromeric duplication and centromeric deletion for chromosome 1(0.10% +/- 0.035%; 0.10% +/- 0.041%, respectively) were significantly increased over that of control group(0.075% +/- 0.023%; 0.060% +/- 0.029%). Our experiments showed that exposed to benzene at higher concentration(42.29 mg/m3) may induce increases in frequencies not only of numerical aberrations for chromosome 1 and 18, but also of structural aberrations for chromosome 1 of sperms in exposed workers.

Adult↗
PubMed1998

Alterations in chromosome structure and variations in the inherent radiation sensitivity of human cells.

Variations in the inherent radiosensitivity of both tumor cells and the normal tissues that surround them play an important role in tumor response to radiation therapy. In vitro studies suggest that variations in radiation sensitivity both between different tissues and within a specific histology are a reflection of differences in the rate and fidelity of rejoining of chromosome breaks. Cells of radiosensitive cell lines rejoin breaks more slowly and with less fidelity than those of more resistant cell lines. Differences in radiation sensitivity are also associated with variations in chromosome structure as detected by nucleoid-based assays. A model is presented to suggest that the radiation sensitivity of a cell line is a reflection of its transcriptional architecture, the number and genomic location of its actively transcribing regions. Also, it is proposed that chromosome breaks induced at or near transcriptionally active regions of the genome are rejoined preferentially and with greater fidelity than breaks induced at other regions of the genome.

Chromosome Aberrations↗
PubMed1999

The phytoestrogens coumoestrol and genistein induce structural chromosomal aberrations in cultured human peripheral blood lymphocytes.

The clastogenic potential of the phytoestrogens coumoestrol (COUM), genistein (GEN) and daidzein (DAI) has been studied in human peripheral blood lymphocytes in vitro. After exposure of the cultured lymphocytes to 50 to 75 microM COUM or 25 microM GEN for 6 h, a clear induction of structural chromosomal aberrations was observed by cytogenetic analysis. The major alterations were chromatid breaks, gaps and interchanges. In contrast, DAI did not induce chromosome aberrations even at 100 microM. These results, together with previously published reports on the induction of micronuclei and DNA strand breaks in cultured Chinese hamster V79 cells by COUM and GEN, but not DAI, suggest that some but not all phytoestrogens have the potential for genetic toxicity.

Adult↗
PubMed1989

5-azacytidine-induced alterations in the GH12C1 cells: effects on cellular morphology, chromosome structure, DNA and protein synthesis.

Growth hormone-producing rat pituitary tumor cells (GH12C1) were cultivated in the presence of 5-azacytidine (5-AC). After cessation of treatment the cells were allowed to recover in normal cell culture medium prior to subcultivation. Within hours after the subcultivation the cells underwent several morphological alterations, later followed by changes in growth pattern: (1) cell shape was irreversibly changed from round or spindle shape to different clones of fibroblast-like cells; (2) some of these clones later formed foci; and (3) an extensive generation of multinucleated cells was seen. The demethylation was maximal approximately one week after the first subcultivation in the absence of 5-AC. Severe alterations of the chromosome structure were seen after the first subcultivation. During the following weeks the 5-AC-treated cells showed impaired chromosome condensation, and homogeneous staining with quinacrine mustard. During this period the DNA synthesis is doubled when compared to control cell DNA synthesis. The core histone synthesis increases in parallel with the DNA synthesis, but the majority of nuclear proteins, including the linker histones, remain at the control level. This results in a ratio of linker histone to core histone synthesis at approximately half the control cell level. The altered ratio of synthesis slowly decreased to control levels during a period of five weeks of continuous cultivation in the absence of the drug, and the under-condensed chromosomes could no longer be seen. The induced novel phenotypes with their pleiomorphic appearances were conserved. The growth hormone synthesis remained constant during all phases of the experiment and prolactin synthesis was not induced.

Animals↗