A postprophase topoisomerase II-dependent chromatid core separation step in the formation of metaphase chromosomes

Juan F. Giménez-Abián, Duncan J. Clarke, Ann M. Mullinger, C. Stephen Downes, Robert T. Johnson

Research output: Contribution to journalArticlepeer-review

89 Scopus citations

Abstract

Metaphase chromatids are believed to consist of loops of chromatin anchored to a central scaffold, of which a major component is the decatenatory enzyme DNA topoisomerase II. Silver impregnation selectively stains an axial element of metaphase and anaphase chromatids; but we find that in earlier stages of mitosis, silver staining reveals an initially single, folded midline structure, which separates at prometaphase to form two chromatid axes. Inhibition of topoisomerase II prevents this separation, and also prevents the contraction of chromatids that occurs when metaphase is arrested. Immunolocalization of topoisomerase IIα reveals chromatid cores analogous to those seen with silver staining. We conclude that the chromatid cores in early mitosis form a single structure, constrained by DNA catenations, which must separate before metaphase chromatids can be resolved.

Original languageEnglish (US)
Pages (from-to)7-17
Number of pages11
JournalJournal of Cell Biology
Volume131
Issue number1
DOIs
StatePublished - Oct 1995

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