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Cell Rep. 2015 Jul 21;12(3):405-17. doi: 10.1016/j.celrep.2015.06.046. Epub 2015 Jul 9.

Both Chromosome Decondensation and Condensation Are Dependent on DNA Replication in C. elegans Embryos.

Author information

1
Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK; MRC Protein Phosphorylation and Ubiquitylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.
2
Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.
3
MRC Protein Phosphorylation and Ubiquitylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.
4
Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK. Electronic address: a.gartner@dundee.ac.uk.
5
Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK. Electronic address: j.j.blow@dundee.ac.uk.

Abstract

During cell division, chromatin alternates between a condensed state to facilitate chromosome segregation and a decondensed form when DNA replicates. In most tissues, S phase and mitosis are separated by defined G1 and G2 gap phases, but early embryogenesis involves rapid oscillations between replication and mitosis. Using Caenorhabditis elegans embryos as a model system, we show that chromosome condensation and condensin II concentration on chromosomal axes require replicated DNA. In addition, we found that, during late telophase, replication initiates on condensed chromosomes and promotes the rapid decondensation of the chromatin. Upon replication initiation, the CDC-45-MCM-GINS (CMG) DNA helicase drives the release of condensin I complexes from chromatin and the activation or displacement of inactive MCM-2-7 complexes, which together with the nucleoporin MEL-28/ELYS tethers condensed chromatin to the nuclear envelope, thereby promoting chromatin decondensation. Our results show how, in an early embryo, the chromosome-condensation cycle is functionally linked with DNA replication.

PMID:
26166571
PMCID:
PMC4521082
DOI:
10.1016/j.celrep.2015.06.046
[Indexed for MEDLINE]
Free PMC Article

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