Accurate chromosome segregation in meiosis requires dynamic changes in chromatin organization. In Drosophila melanogaster, upon completion of recombination, meiotic chromosomes form a single, compact cluster called the karyosome in an enlarged oocyte nucleus. This clustering is also found in humans; however, the mechanisms underlying karyosome formation are not understood. In this study, we report that phosphorylation of barrier to autointegration factor (BAF) by the conserved kinase nucleosomal histone kinase-1 (NHK-1; Drosophila Vrk1) has a critical function in karyosome formation. We find that the noncatalytic domain of NHK-1 is crucial for its kinase activity toward BAF, a protein that acts as a linker between chromatin and the nuclear envelope. A reduction of NHK-1 or expression of nonphosphorylatable BAF results in ectopic association of chromosomes with the nuclear envelope in oocytes. We propose that BAF phosphorylation by NHK-1 disrupts anchorage of chromosomes to the nuclear envelope, allowing karyosome formation in oocytes. These data provide the first mechanistic insight into how the karyosome forms.
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3 December 2007
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November 26 2007
NHK-1 phosphorylates BAF to allow karyosome formation in the Drosophila oocyte nucleus
Oscar M. Lancaster,
Oscar M. Lancaster
The Wellcome Trust Centre for Cell Biology, The University of Edinburgh, Edinburgh EH9 3JR, Scotland, UK
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C. Fiona Cullen,
C. Fiona Cullen
The Wellcome Trust Centre for Cell Biology, The University of Edinburgh, Edinburgh EH9 3JR, Scotland, UK
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Hiroyuki Ohkura
Hiroyuki Ohkura
The Wellcome Trust Centre for Cell Biology, The University of Edinburgh, Edinburgh EH9 3JR, Scotland, UK
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Oscar M. Lancaster
The Wellcome Trust Centre for Cell Biology, The University of Edinburgh, Edinburgh EH9 3JR, Scotland, UK
C. Fiona Cullen
The Wellcome Trust Centre for Cell Biology, The University of Edinburgh, Edinburgh EH9 3JR, Scotland, UK
Hiroyuki Ohkura
The Wellcome Trust Centre for Cell Biology, The University of Edinburgh, Edinburgh EH9 3JR, Scotland, UK
Correspondence to Hiroyuki Ohkura: [email protected]
Abbreviations used in this paper: BAF, barrier to autointegration factor; MBP, maltose-binding protein; NHK-1, nucleosomal histone kinase-1; UASp, upstream activating sequence.
Received:
June 11 2007
Accepted:
October 31 2007
Online ISSN: 1540-8140
Print ISSN: 0021-9525
The Rockefeller University Press
2007
J Cell Biol (2007) 179 (5): 817–824.
Article history
Received:
June 11 2007
Accepted:
October 31 2007
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Citation
Oscar M. Lancaster, C. Fiona Cullen, Hiroyuki Ohkura; NHK-1 phosphorylates BAF to allow karyosome formation in the Drosophila oocyte nucleus . J Cell Biol 3 December 2007; 179 (5): 817–824. doi: https://doi.org/10.1083/jcb.200706067
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