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 II alpha 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.
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October 01 1995
A postprophase topoisomerase II-dependent chromatid core separation step in the formation of metaphase chromosomes.
J F Giménez-Abián,
J F Giménez-Abián
Department of Zoology, University of Cambridge, United Kingdom.
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D J Clarke,
D J Clarke
Department of Zoology, University of Cambridge, United Kingdom.
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A M Mullinger,
A M Mullinger
Department of Zoology, University of Cambridge, United Kingdom.
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C S Downes,
C S Downes
Department of Zoology, University of Cambridge, United Kingdom.
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R T Johnson
R T Johnson
Department of Zoology, University of Cambridge, United Kingdom.
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J F Giménez-Abián
Department of Zoology, University of Cambridge, United Kingdom.
D J Clarke
Department of Zoology, University of Cambridge, United Kingdom.
A M Mullinger
Department of Zoology, University of Cambridge, United Kingdom.
C S Downes
Department of Zoology, University of Cambridge, United Kingdom.
R T Johnson
Department of Zoology, University of Cambridge, United Kingdom.
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1995) 131 (1): 7–17.
Citation
J F Giménez-Abián, D J Clarke, A M Mullinger, C S Downes, R T Johnson; A postprophase topoisomerase II-dependent chromatid core separation step in the formation of metaphase chromosomes.. J Cell Biol 1 October 1995; 131 (1): 7–17. doi: https://doi.org/10.1083/jcb.131.1.7
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