ISWI remodeling complexes in Xenopus egg extracts: identification as major chromosomal components that are regulated by INCENP-aurora B.
We previously characterized major components of mitotic chromosomes assembled in Xenopus laevis egg extracts and collectively referred to them as Xenopus chromosome-associated polypeptides (XCAPs). They included five subunits of the condensin complex essential for chromosome condensation. In an effort to identify novel proteins involved in this process, we have isolated XCAP-F and found it to be the Xenopus ortholog of ISWI, a chromatin remodeling ATPase. ISWI exists in two major complexes in Xenopus egg extracts. The first complex contains ACF1 and two low-molecular-weight subunits, most likely corresponding to Xenopus CHRAC. The second complex is a novel one that contains the Xenopus ortholog of the human Williams syndrome transcription factor (WSTF). In the absence of the ISWI complexes, the deposition of histones onto DNA is apparently normal, but the spacing of nucleosomes is greatly disturbed. Despite the poor spacing of nucleosomes, ISWI depletion has little effect on DNA replication, chromosome condensation or sister chromatid cohesion in the cell-free extracts. The association of ISWI with chromatin is cell cycle regulated and is under the control of the INCENP-aurora B kinase complex that phosphorylates histone H3 during mitosis. Apparently contradictory to the generally accepted model, we find that neither chromosome condensation nor chromosomal targeting of condensin is compromised when H3 phosphorylation is drastically reduced by depletion of INCENP-aurora B.
MacCallum
David E
DE
Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, NY 11724, USA.
Losada
Ana
A
Kobayashi
Ryuji
R
Hirano
Tatsuya
T
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D064107:Aurora Kinase B; D064127:Aurora Kinases; D002457:Cell Extracts / Q000032:analysis; D002478:Cells, Cultured; D002843:Chromatin / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D002875:Chromosomes / Q000737:chemistry / Q000378:metabolism*; D003001:Cloning, Molecular; D005260:Female; D006657:Histones / Q000378:metabolism; D008297:Male; D008938:Mitosis; D009687:Nuclear Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D009707:Nucleosomes / Q000378:metabolism; D010063:Ovum / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D021122:Protein Subunits; D014157:Transcription Factors / Q000378:metabolism*; D014981:Xenopus; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*
C492320:BAZ1A protein, Xenopus; D002457:Cell Extracts; D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D006657:Histones; C086468:ISWI protein; D009687:Nuclear Proteins; D009707:Nucleosomes; D021122:Protein Subunits; D014157:Transcription Factors; D029867:Xenopus Proteins; C576921:AURKB protein, human; D064107:Aurora Kinase B; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases; D000251:Adenosine Triphosphatases