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At least 1,117 records · Page 62Linked to original sources
PubMed1989

Chromosome specificity of satellite DNAs: short- and long-range organization of a diverged dimeric subset of human alpha satellite from chromosome 3.

The human alpha satellite DNA family, like many highly repeated satellite DNAs in eukaryotic genomes, is organized in distinct chromosome-specific subsets. As part of investigations into the molecular and evolutionary basis for the chromosome-specific nature of such subsets, we report the isolation and characterization of alpha satellite sequences specific for human chromosome 3. This subset is characterized by a predominant tandemly arranged approximately 2.9 kb higher-order repeat unit which, in turn, consists of 17 tandem diverged monomer repeat units of approximately 171 bp. Nucleotide sequence analysis reveals that the chromosome 3 higher-order repeat units are comprised, at least in part, of diverged dimeric (approximately 340 bp) sub-repeats and that this divergence accounts for the chromosome-specific behavior of this subset. Pulsed-field gel electrophoresis demonstrates that the chromosome 3 higher-order repeat units are localized in large domains, at least 1000 kb in length. Familial restriction fragment length polymorphisms associated with the satellite subset can be detected by pulsed-field gel electrophoresis and may facilitate molecular analysis of interchromosomal variation.

Base Sequence↗
PubMed1982

In situ immunofluorescent visualization of chromosomal transcripts in polytene chromosomes.

The induction and distribution of chromosomal transcripts in the polytene chromosomes of D. melanogaster and D. hydei has been investigated by indirect immunofluorescence using an antiserum directed against DNA/RNA hybrids. The fluorescence was intense and occurred in most of the chromosomal subdivisions when the chromosomes were exposed to denaturing conditions and then allowed to reanneal. The extent of hybrid formation depended both on the extent of DNA denaturation and on the maintenance of RNA integrity. Fluorescence was absent from chromosomes treated with pancreatic RNase before denaturation. The velocity of the chromosomal DNA/RNA hybridization reaction and the effects of the initiation inhibitor of RNA synthesis, DRB, suggest that in order to hybridize the RNA has to be located in its transcriptional compartment. Even though overall patterns of fluorescence seem to be similar during a developmental stage, variations were observed, particularly some correlated with puff induction after ecdysone stimulation.

Animals↗
PubMed1976

Pairing and segregation of the sex chromosomes in X1X2-males of Dysdercus intermedius with a note on the kinetic organization of heteropteran chromosomes.

The existence of an X1X2-mode of sex determination is confirmed by a study of all meiotic stages in the male cotton stainer (X1X2) and pertinent stages in the female (X1X1X2X2). In the male, the X-chromosomes are heterochromatic and pair end-to-end in early meiotic prophase. At diakinesis, they disjoin and align side-by-side in the center of the spindle, forming a pseudotetrad. Anaphase I is equational for the sex chromosomes. At late anaphase or telephase, X1 and X2 join end-to-end but form spindle fiber connections to only one of the poles of the metaphase II spindle, leading to one daughter cell without X chromosomes and one with both X1 and X2. An attempt is made to explain sex chromosome pairing and orientation on the basis of a telocentric organization of meiotic chromosomes. The apparent differences in the kinetic organization of mitotic and meiotic chromosomes in Heteroptera are discussed.

Animals↗
PubMed1994

Assignment of RFLP, RAPD and isoenzyme markers to Aspergillus nidulans chromosomes, using chromosome-substituted segregants of a hybrid of A. nidulans and A. quadrilineatus.

Chromosome-substituted haploid segregants were selected from among the benomyl-induced progeny of an interspecific hybrid produced by polyethylene-glycol-induced fusion of protoplasts of an Aspergillus nidulans 'master strain' and an A. quadrilineatus auxotrophic mutant. These segregants were examined by RFLP, RAPD, and isoenzyme analysis. The A. nidulans ribosomal repeat unit was assigned to chromosome V, while the benA and the pyrG genes were assigned to linkage groups VIII and I, respectively, of A. nidulans. None of the other cloned genes tested (gdhA, amdS and 25s rRNA) showed polymorphism between the two parents. The method was also used to assign RAPD markers and isoenzyme bands of beta-arylesterase, phosphatases, NAD-dependent malate dehydrogenase, and cellulase, to A. nidulans chromosomes and/or to their A. quadrilineatus equivalents. The isoenzyme and DNA sequences assigned to chromosomes could be used to saturate the genetic map of A. nidulans, or could serve as starting points for the construction of a genetic map of A. quadrilineatus. No method affording the same possibilities has been described so far in Aspergilli. This chromosome-assay method may be a useful alternative to pulsed-field-gel electrophoretic procedures for the assignment of molecular markers to chromosomes.

Aspergillus↗
PubMed1992

Involvement of chromatid cohesiveness at the centromere and chromosome arms in meiotic chromosome segregation: a cytological approach.

Kinetochores and chromatid cores of meiotic chromosomes of the grasshopper species Arcyptera fusca and Eyprepocnemis plorans were differentially silver stained to analyse the possible involvement of both structures in chromatid cohesiveness and meiotic chromosome segregation. Special attention was paid to the behaviour of these structures in the univalent sex chromosome, and in B univalents with different orientations during the first meiotic division. It was observed that while sister chromatids of univalents are associated at metaphase I, chromatid cores are individualised independently of their orientation. We think that cohesive proteins on the inner surface of sister chromatids, and not the chromatid cores, are involved in the chromatid cohesiveness that maintains associated sister chromatids of bivalents and univalents until anaphase I. At anaphase I sister chromatids of amphitelically oriented B univalents or spontaneous autosomal univalents separate but do not reach the poles because they remain connected at the centromere by a long strand which can be visualized by silver staining, that joins stretched sister kinetochores. This strand is normally observed between sister kinetochores of half-bivalents at metaphase II and early anaphase II. We suggest that certain centromere proteins that form the silver-stainable strand assure chromosome integrity until metaphase II. These cohesive centromere proteins would be released or modified during anaphase II to allow normal chromatid segregation. Failure of this process during the first meiotic division could lead to the lagging of amphitelically oriented univalents. Based on our results we propose a model of meiotic chromosome segregation. During mitosis the cohesive proteins located at the centromere and chromosome arms are released during the same cellular division.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1975

Replication of human chromosomes in human-mouse hybrids: evidence that the timing of DNA synthesis is determined independently in each human chromosome.

The terminal phase of DNA replication was studied by autoradiography in hybrids between human lymphocytes and mouse fibroblasts. The hybrids contained on the average only 11 human chromosomes. It was found that the sequence of terminal DNA replication for the human chromosomes in the hybrids was the same as the sequence of terminal replication for the corresponding chromosomes in the human lymphocytes. Furthermore, it was shown that the maintenance of the normal terminal replication sequence of the human chromosomes in the hybrids was not dependent on the presence of any specific human chromosome. The results suggest that the timing of terminal DNA replication is determined independently in each human chromosome.

Animals↗
PubMed1978

Assignment of the genes for triose phosphate isomerase to chromosome 6 and tripeptidase-1 to chromosome 10 in Mus musculus by somatic cell hybridization.

Evidence is presented for the assignment of the gene for triose phosphate isomerase to Mus musculus chromosome 6 and tripeptidase-1 to chromosome 10 by synteny testing and chromosome assignment in Chinese hamster X mouse somatic cell hybrid clones. Neither TPI nor TRIP-1 were expressed concordantly with any known isozyme markers in 45 hybrid clones (13 primary and 32 secondary). Karyotypic analysis of 21 clones showed that the expression of TPI and chromosome 6 were concordant in all cases as was expressed of TRIP-1 and chromosome 10. Both chromosomes were previously unmarked by isozymes.

Aminopeptidases↗
PubMed2000

The Xenopus chromokinesin Xkid is essential for metaphase chromosome alignment and must be degraded to allow anaphase chromosome movement.

At anaphase, the linkage betweeh sister chromatids is dissolved and the separated sisters move toward opposite poles of the spindle. We developed a method to purify metaphase and anaphase chromosomes from frog egg extracts and identified proteins that leave chromosomes at anaphase using a new form of expression screening. This approach identified Xkid, a Xenopus homolog of human Kid (kinesin-like DNA binding protein) as a protein that is degraded in anaphase by ubiquitin-mediated proteolysis. Immunodepleting Xkid from egg extracts prevented normal chromosome alignment on the metaphase spindle. Adding a mild excess of wild-type or nondegradable Xkid to egg extracts prevented the separated chromosomes from moving toward the poles. We propose that Xkid provides the metaphase force that pushes chromosome arms toward the equator of the spindle and that its destruction is needed for anaphase chromosome movement.

Amino Acid Sequence↗
PubMed1995

Characterization of a 14q+ marker chromosome in philadelphia chromosome positive acute lymphoblastic leukemia by DNA analysis and fluorescence in situ hybridization.

We report a case of precursor-B acute lymphoblastic leukemia (ALL) with the Philadelphia chromosome (Ph) and a 14q+ chromosome whose additional material was a part of the long arm of der(9)t(9;22). A minor population carrying the standard Ph translocation without the 14q+ was also observed at the first presentation. The translocation of the BCR gene from chromosome 22 to the subtelomeric region of the 14q+ was confirmed by fluorescence in situ hybridization (FISH) using a yeast artificial chromosome (YAC) clone containing the BCR gene. The breakpoint of chromosome 14 could not be determined exactly but probably was at 14q24 or 14q32 by conventional chromosome analysis. Nevertheless, FISH using a YAC clone containing the human immunoglobulin heavy chain (IgH) gene locus, Southern blot, and pulsed-field gel electrophoresis (PFGE) analyses with IgJH probe, and loss of heterozygosity analysis at the alpha 1-antitrypsin (AT) gene locus showed lack of involvement of the IgH gene in the 14q+ and more centromeric breakage than the alpha 1-AT locus at 14q32.1. Thus, the formation of the 14q+ seemed to be a secondary genetic event after the Ph translocation and presumably played a minor role in the pathogenesis of B-cell malignancy in this case.

Base Sequence↗
PubMed1998

Meiotin-1, a meiosis-enriched protein present in normal leptotene chromosomes and lacking in precociously condensed leptotene chromosomes.

During mitotic prophase, chromosomes progressively compact to their metaphase length. In contrast, meiotic chromosomes condense moderately until late in prophase I, then they condense more dramatically (coil) to their fully condensed state. Meiotin-1 is a meiosis-enriched, chromosomal protein. We propose that it delays coiling until after reciprocal genetic exchange. We have used immunoblotting and immunocytochemistry with normal lily cells undergoing meiosis to demonstrate that meiotin-1 is present during the early portions of prophase I, but diminishes at the time when meiotic chromosomes begin to coil. Additionally, we have examined lily meiotic nuclei undergoing the reversible phenomenon of precocious leptotene chromosome condensation (precocious coiling). The leptotene chromosomes that are precociously condensed lack meiotin-1 immunostaining. Furthermore nuclei returning to the normal state of moderate prophase I condensation acquire meiotin-1.

Antibodies, Monoclonal↗
PubMedDate not supplied

Chromosome 7 aneusomy. A marker for metastatic melanoma? Expression of the epidermal growth factor receptor gene and chromosome 7 aneusomy in nevi, primary malignant melanomas and metastases.

Receptor tyrosine kinases such as the epidermal growth factor receptor (EGFR) play an important role in a variety of malignant neoplasias, making the search for aberrations in the relevant chromosomes an important issue. Differential expression of the EGFR gene was investigated by reverse transcriptase (RT)-PCR on tissue samples of normal skin, nevi, primary melanomas, and melanoma metastases. The EGFR gene is located on chromosome 7p12.3-p12.1. To determine the number of chromosomes 7 in cell nuclei of the mentioned tissue samples we performed fluorescence in situ hybridization (FISH) on touch preparations, using a DNA probe that hybridizes specifically to the centromeric region of chromosome 7. Additionally, chromosome 7 number in interphase nuclei was determined in short-term primary cell cultures of nevi, primary melanomas, and metastases. The highest EGFR gene expression frequency was found in melanoma metastases. By FISH we detected the highest fraction of cell nuclei with more than two chromosomes 7 in the group of metastases. Our results suggest that overexpression of the EGFR gene might play an important role in metastasis of malignant melanoma. This is well reflected by polysomy 7, possibly accounting for an increased EGFR gene copy number.

Aneuploidy↗
PubMed1998

Molecular cloning and chromosomal localization of Chinese hamster telomeric protein chTRF1. Its potential role in chromosomal instability.

Chinese hamster cells frequently have altered karyotypes. To investigate the basis of recent observations that karyotypic alterations are related to telomeric fusions, we asked whether these alterations are due to lack of telomere repeat binding factor/s. Further, Chinese hamster chromosomes contain large blocks of interstitial telomeric repeats, which are preferentially involved in chromosome breakage and exchange, rendering it an interesting model for such studies. Here, we report on the cloning and the chromosomal localization of the Chinese hamster telomere repeat binding factor, chTRF1. The sequence analysis revealed, similar to human TRF1 (hTRF1), an N-terminal acidic domain, a TRF1 specific DNA binding motif and a C-terminal Myb type domain. Unlike mouse TRF1 (mTRF1), chTRF1 shows 97.5% identity to hTRF1. chTRF1 gene was localized on the long arm of chromosome 5. In vitro translation of chTRF1 resulted in protein product similar in molecular weight to hTRF1. Immunostaining of Chinese hamster ovary cells (CHO) with anti-TRF1 antibody revealed punctate nuclear staining. At metaphase, antibodies failed to detect TRF1 on most of the chromosome ends and the interstitial telomeric repeat bands. These studies suggest that chTRF1 does not bind the interstitial telomeric repeats, and its presence at the metaphase chromosome ends is limited. The later could be a factor contributing to frequent karyotypic alterations observed in Chinese hamster cells.

Amino Acid Sequence↗
PubMed1996

Prognostic significance of additional chromosome abnormalities in adult patients with Philadelphia chromosome positive acute lymphoblastic leukaemia.

The clinical and biological significance of additional chromosome aberrations was investigated in a large series of 66 adult patients with Philadelphia (Ph) chromosome positive acute lymphoblastic leukaemia (ALL). Additional chromosome changes were observed in 71% of the cases. 9p abnormalities were identified in 26%, and monosomy 7 as well as hyperdiploid karyotypes 50 were both found in 17% of cases. 9p anomalies were characterized by a low complete remission (CR) rate (58%) and an extremely short median remission duration (MRD: 100 d). In patients with monosomy 7, the poor treatment outcome was confirmed (CR rate 55%: MRD 113 d). In contrast, all patients with hyperdiploid karyotypes 50 achieved CR, and the overall survival was superior to all other Ph-positive ALL patients except those without additional chromosome aberrations. Exclusive rearrangement of the minor breakpoint cluster region of the BCR gene and lack of coexpression of myeloid-associated antigens in cases with 9p anomalies as well as a high frequency of rearrangements of the major breakpoint cluster region of the BCR gene in patients with monosomy 7 (89%) further substantiated that additional chromosome aberrations may characterize distinct subgroups of Ph-positive ALL. Moreover, the necessity of the complementing use of chromosome banding analyses, polymerase chain reaction (PCR) assays, and fluorescence in situ hybridizations in the accurate identification of Ph-positive patients has become evident due to variant Ph translocations in 3%, and negative PCR assays in 4% of the cases.

Adolescent↗
PubMed2001

Interplay between recombination, cell division and chromosome structure during chromosome dimer resolution in Escherichia coli.

Chromosome dimers form in bacteria by recombination between circular chromosomes. Resolution of dimers is a highly integrated process involving recombination between dif sites catalysed by the XerCD recombinase, cell division and the integrity of the division septum-associated FtsK protein and the presence of dif inside a restricted region of the chromosome terminus, the dif activity zone (DAZ). We analyse here how these phenomena collaborate. We show that (i) both inter- and intrachromosomal recombination between dif sites are activated by their presence inside the DAZ; (ii) the DAZ-specific activation only occurs in conditions supporting the formation of chromosome dimers; (iii) overexpression of FtsK leads to a general increase in dif recombination irrespective of dif location; (iv) overexpression of FtsK does not improve the ability of dif sites inserted outside the DAZ to resolve chromosome dimers. Our results suggest that the formation of an active XerCD-FtsK-dif complex is restricted to when a dimer is present, the features of chromosome organization that determine the DAZ playing a central role in this control.

Bacterial Proteins↗
PubMed1994

Structural analysis of chromosomal rearrangements associated with the developmental mutations Ph, W19H, and Rw on mouse chromosome 5.

We are studying the chromosomal structure of three developmental mutations, dominant spotting (W), patch (Ph), and rump white (Rw) on mouse chromosome 5. These mutations are clustered in a region containing three genes encoding tyrosine kinase receptors (Kit, Pdgfra, and Flk1). Using probes for these genes and for a closely linked locus, D5Mn125, we established a high-resolution physical map covering approximately 2.8 Mb. The entire chromosomal segment mapped in this study is deleted in the W19H mutation. The map indicates the position of the Ph deletion, which encompasses not more than 400 kb around and including the Pdgfra gene. The map also places the distal breakpoint of the Rw inversion to a limited chromosomal segment between Kit and Pdgfra. In light of the structure of the Ph-W-Rw region, we interpret the previously published complementation analyses as indicating that the pigmentation defect in Rw/+ heterozygotes could be due to the disruption of Kit and/or Pdgfra regulatory sequences, whereas the gene(s) responsible for the recessive lethality of Rw/Rw embryos is not closely linked to the Ph and W loci and maps proximally to the W19H deletion. The structural analysis of chromosomal rearrangements associated with W19H, Ph, and Rw combined with the high-resolution physical mapping points the way toward the definition of these mutations in molecular terms and isolation of homologous genes on human chromosome 4.

Animals↗
PubMed1995

Isolation of yeast artificial chromosomes free of endogenous yeast chromosomes: construction of alternate hosts with defined karyotypic alterations.

An intrinsic feature of yeast artificial chromosomes (YACs) is that the cloned DNA is generally in the same size range (i.e., approximately 200-2000 kb) as the endogenous yeast chromosomes. As a result, the isolation of YAC DNA, which typically involves separation by pulsed-field gel electrophoresis, is frequently confounded by the presence of a comigrating or closely migrating endogenous yeast chromosome(s). We have developed a strategy that reliably allows the isolation of any YAC free of endogenous yeast chromosomes. Using recombination-mediated chromosome fragmentation, a set of Saccharomyces cerevisiae host strains was systematically constructed. Each strain contains defined alterations in its electrophoretic karyotype, which provide a large-size interval devoid of endogenous chromosomes (i.e., a karyotypic "window"). All of the constructed strains contain the kar1-delta 15 mutation, thereby allowing the efficient transfer of a YAC from its original host into an appropriately selected window strain using the kar1-transfer procedure. This approach provides a robust and efficient means to obtain relatively pure YAC DNA regardless of YAC size.

Chromosomes, Artificial, Yeast↗
PubMed2004

Aurora kinase inhibitor ZM447439 blocks chromosome-induced spindle assembly, the completion of chromosome condensation, and the establishment of the spindle integrity checkpoint in Xenopus egg extracts.

The Aurora family kinases contribute to accurate progression through several mitotic events. ZM447439 ("ZM"), the first Aurora family kinase inhibitor to be developed and characterized, was previously found to interfere with the mitotic spindle integrity checkpoint and chromosome segregation. Here, we have used extracts of Xenopus eggs, which normally proceed through the early embryonic cell cycles in the absence of functional checkpoints, to distinguish between ZM's effects on the basic cell cycle machinery and its effects on checkpoints. ZM clearly had no effect on either the kinetics or amplitude in the oscillations of activity of several key cell cycle regulators. It did, however, have striking effects on chromosome morphology. In the presence of ZM, chromosome condensation began on schedule but then failed to progress properly; instead, the chromosomes underwent premature decondensation during mid-mitosis. ZM strongly interfered with mitotic spindle assembly by inhibiting the formation of microtubules that are nucleated/stabilized by chromatin. By contrast, ZM had little effect on the assembly of microtubules by centrosomes at the spindle poles. Finally, under conditions where the spindle integrity checkpoint was experimentally induced, ZM blocked the establishment, but not the maintenance, of the checkpoint, at a point upstream of the checkpoint protein Mad2. These results show that Aurora kinase activity is required to ensure the maintenance of condensed chromosomes, the generation of chromosome-induced spindle microtubules, and activation of the spindle integrity checkpoint.

Animals↗
PubMed1990

Recombination in the B chromosome of maize to produce A-B-A chromosomes.

The translocations between the supernumerary B chromosomes and the normal A chromosomes of maize provide a valuable tool for gene localizations, dosage studies and characterization of mutants as null, leaky or gain-of-function. A procedure is described, that relies on recombination in the B chromosome, for marking each of the various B-A translocations with a single dominant marker that will allow dosage classifications of individuals at the mature kernel stage. This marker is R-scm3, which conditions anthocyanin pigment in the aleurone of the endosperm and the scutellum of the embryo. A test for recombination in the B chromosome was conducted by crossing together two translocations, that were broken on opposite sides of the B centromere, and in different A chromosome arms, namely TB-1La and TB-10L18. An example was recovered that linked genetic markers on 1L and 10L to the B centromere. Cytological examination at pachytene of meiosis confirmed the new chromosomal linkage. The use of this procedure to produce a comprehensive set of uniformly marked B-A translocations is discussed.

Anthocyanins↗