Centromeres, DNA

Centromer-specific H3 variants (CenH3 s) are known as CENP-A in mammals, Cid in flies, Cse4 in yeast (Fig. 1 Table 1 reviewed in Smith 2002). CenH3 s are incorporated into nucleosomes independently of centromeric DNA replication. CenH3-containing nucleosomes associate with a number of factors with important roles in centromere structure and kinetochore assembly. Recently, the deposition complex... 

For repetitive DNA sequences, such as alphoid repeats, especially for identification of centromeric regions on chromosomes, as well as in mterphase nuclei, I routinely prepare labeled probes by PCR using a centromeric DNA-specific set of primers. For single-copy gene mapping by FISH, it is essential to use DNA cloned into either cosmids or in yeast artificial chromosome vectors (YAC) m order to obtain the level of sensitivity that will enable visualization of signal with a fluorescence microscope... 

The density, p, of a double stranded DNA molecule, and hence its position in the gradient, depends primarily on its nucleotide composition (eq. 2.2 gives p= 1.660+0.098 (GC)). The relation does not hold for DNAs containing glucosylated, methylated or other modified residues, nor for DNAs of very simple sequence such as synthetic polynucleotides, crab poly dAT (Wells et al. 1970) and centromeric DNA. Single stranded DNA is denser than double stranded DNA and isopycnic centrifugation can be used to separate them. 

Micronuclei formed by aneuploidy induction can be distingnished from those produced by clastogenic activity by the presence of centromeric DNA or kinetochore... 

Cheeseman, I. M., D. G. Drubin, and G. Barnes. 2002. Simple centromere, complex kinetochore linking spindle microtubules and centromeric DNA in budding yeast. J. Cell Biol. 157 199-203. 

In all eukaryotes, three components participate in attaching chromosomes to microtubules the centromere, kinetochore and spindle proteins, and the cell-cycle machinery. The location of the centromere and hence that of the kinetochore Is directly controlled by a specific sequence of chromosomal DNA termed centromeric DNA (Chapter 10). Although the sequences of centromeric DNA and of DNA-binding proteins In the kinetochore are not well conserved through evolution, the cell-cycle proteins and many of the... 

Fig. 6.37. Two approaches for manipulation of a human chromosome. (A) Minichromosomes can be generated in cultured cells by chromosome truncation mediated by the integration of telomeric sequences into chromosome arms. (B) Alternatively, artificial chromosomes might be constructed by combining the known functional elements of a human chromosome telomeric DNA, centromeric DNA, and genomic DNA containing a human gene or selectable genetic marker.

Stinchcomb DT, Mann C, Davis RW (1982) Centromeric DNA from Saccharomyces cerevi-siae. J Mol Biol 158 157-190... 

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