Biomedical subjects

D Broccoli

Publications and source records attributed to D Broccoli.

24 records · Page 2Linked to original sources

PubMed1991

Isolation of a variant family of mouse minor satellite DNA that hybridizes preferentially to chromosome 4.

Two cosmids (HRS-1 and HRS-2) containing mouse minor satellite DNA sequences have been isolated from a mouse genomic library. In situ hybridization under moderate stringency conditions to metaphase chromosomes from RCS-5, a tumor cell line derived from the SJL strain, mapped both HRS-1 and HRS-2 to the centromeric region of chromosome 4. Sequence data indicate that these cloned minor satellite DNA sequences have a basic higher order repeat of 180 bp, composed of three diverged 60-bp monomers. Digestion of mouse genomic DNA with several restriction enzymes produces a ladder of minor satellite fragments based on a 120-bp repeat. The restriction enzyme NlaIII (CATG) digests all the minor satellite DNA into three prominent bands of 120, 240, and 360 bp and a weak band of 180 bp. Thus, the majority of minor satellite sequences in the genome are arranged in repeats based on a 120-bp dimer, while the family of minor satellite sequences described here represents a rare variant of these sequences. Our results raise the possibility that there may be other variant families of minor satellites analogous to those of alphoid DNA present in humans.

Animals↗

PubMed1990

Relationship of mouse minor satellite DNA to centromere activity.

Chromosomes from a female mouse cell line were identified by Q-banding prior to in situ hybridization with 3H-labeled mouse minor satellite (satellite II) DNA. No cell was found in which every chromosome was labeled, but grain counts showed that every active centromeric region had minor satellite sequences. In the mouse T (10;13)199H translocation, the breakpoint was within the minor satellite array, leaving clusters of minor satellite at the C-bandless active centromere of the 13(10) chromosome and at the interstitial C-band of the 10(13) chromosome, which is not associated with centromeric activity. In a mouse A9 (L-cell derived) marker chromosome with one terminal and two interstitial C-bands, only the terminal C-band was adjacent to an active centromere, but minor satellite DNA was present at all three sites. Minor satellite DNA was not detected on the Y chromosome, although the presence of a small amount of divergent satellite sequences on this chromosome could not be ruled out.

Animals↗

PubMed1989

Sequence of centromere separation: characterization of multicentric chromosomes in a rat cell line.

The B1 cell line of rat cerebral endothelium origin exhibits several dicentric and multicentric chromosomes. These chromosomes, unlike multicentrics in mouse (Vig and Zinkowski 1986) do not show premature centromere separation. All centromeres deposit kinetochore proteins and appear to be functional. Even the centromeres which fail to migrate to the poles during anaphase and make side arm bridges bind to spindle microtubules. Some multicentric chromosomes show kinetochores spaced apart with intervening stretches of euchromatin while others are located adjacent to each other thus exhibiting tandem repeats and forming a "compound" kinetochore (Brinkeley et al. 1984). Also, unlike mouse multicentric chromosomes in which different pericentric regions and the centromeres replicate at different times, the rat chromosomes appear to replicate all pericentric and centric regions in a given multicentric simultaneously. The present studies indicate that centromeres in rat and mouse replicate during the last part of the S-phase and in continuation with the pericentric heterochromatin.

Animals↗

PubMed1989

Centromere separation and aneuploidy: a lesson from multicentric chromosomes.

Premature centromere separation somehow nullifies the deposition of kinetochore proteins in multicentric chromosomes, is associated with early DNA replication of the centromere and the pericentric region and results in a lack of functionality of the centromere. It is conceivable that monocentric chromosomes which show premature separation, like the X chromosome as found in elderly human females (Fitzgerald et al, 1975), may have similar properties which result in a failure of centromere function and, hence, aneuploidy. This may be one of the general mechanisms by which chromosomes malsegregate.

Aneuploidy↗

PubMed1988

Sequence of centromere separation: differential replication of pericentric heterochromatin in multicentric chromosomes.

The dicentric and multicentric chromosomes in L cells and a brain tumor cell line of mouse display only one site of kinetochore formation associated with the 'active' centromere. The accessory or 'inactive' centromeres show premature separation. These cell lines were treated with 10(-6) M 5-bromodeoxyuridine (BrdUrd) followed by anti-BrdUrd antibody to study the pattern of replication of pericentric heterochromatin flanking the active vs inactive centromeres. Regardless of its quantity, heterochromatin around the inactive centromere replicates earlier than that associated with the active centromere. There appears to be a relationship between the timing of separation of a centromere and the timing of replication of pericentric heterochromatin. The premature replication of heterochromatin associated with an inactive centromere may be responsible for its premature separation and, hence, inactivity.

Animals↗

PubMed1986

Characterization of kinetochores in multicentric chromosomes.

Long-term cultures of certain rat and mouse cell lines carry several dicentric and some multicentric chromosomes. Using antikinetochore antibodies obtainable from serum of scleroderma (var. CREST) patients we studied the number of kinetochores formed along the length of these chromosomes. The rat cells displayed as many kinetochores as there were centromeres. However, mouse cells showed the synthesis of only one kinetochore in dicentric and multicentric chromosomes which had been in the culture for a period of 1 year or more. When translocations were induced by bleomycin in mouse L cells, the newly formed dicentric chromosomes showed the formation of two kinetochores. It is not known when the accessory centromeres lose their capacity to assemble kinetochore proteins. Possibly, in the rat the 'latent' kinetochore lack a specific component which renders them ineffective for microtubule binding. The reason for the formation of only one kinetochore in mouse multicentric chromosomes is not clear. It may be due to the accumulation of mutations, modification of the kinetochore protein so that it lacks the antibody binding component, or a more effective regulatory gene than in the rat.

Animals↗