Multiple chromosomal populations of topoisomerase II detected in vivo by time-lapse, three-dimensional wide-field microscopy

Article Abstract:

A study analyzes the in vivo distribution of DNA topoisomerase II (topo II) during the cell cycle of living Drosophila melanogaster embryos through time-lapse, three-dimensional, wide-field sequences. The nucleus is revealed to have three separate topo II populations of a spatially and temporally regulated localization. Topo II's exodus from the nucleus during mitosis and its ability to localize on sites which are precisely needed by the chromosome indicate the impact of separate pools on chromosome condensation and topo II's use in forecasting structural dynamics in chromosomes.

Chromosome mapping, Mitosis, DNA topoisomerase II

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Perturbation of nuclear architecture by long-distance chromosome interactions

Article Abstract:

The nuclear architecture is disrupted by long-distance chromosome interactions that cause stochastic transcriptional silencing of genes that are present near heterochromatin (position-effect variegation). In the Drosophila embryonic nuclei, a heterochromatic insertion at the brown locus is spatially isolated from other heterochromatin. During larval development, this insertion physically associates with other heterochromatic regions on the same chromosome in a stochastic manner. The frequency of long distance interactions is highest in the interphase nuclei.

Causes of, Physiological aspects, Chromatin, Suppression, Genetic, Suppressor mutation (Molecular genetics), Cooperative binding (Biochemistry)

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Direct evidence of a role for heterochromatin in meiotic chromosome segregation

Article Abstract:

A study on the mechanism that enables achiasmate chromosomes to separate at meiosis I in Drosophila melanogaster oocytes used innovative cytological methods to determine whether nonexchange chromosomes are paired before disjunction. Results show that the heterochromatin of homologous chromosomes is associated from prophase to metaphase I whether or not exchange takes place. This implies that homologous recognition can lead to segregation even without chiasmata.

Chromosomes, Meiosis

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