Chromosomes with delayed replication timing lead to checkpoint activation, delayed recruitment of Aurora B and chromosome instability.
Certain chromosome rearrangements display a significant delay in chromosome replication timing (DRT) that is associated with a subsequent delay in mitotic chromosome condensation (DMC). DRT/DMC chromosomes are common in tumor cells in vitro and in vivo and occur frequently in cells exposed to ionizing radiation. A hallmark for these chromosomes is the delayed phosphorylation of serine 10 of histone H3 during mitosis. The chromosome passenger complex, consisting of multiple proteins including Aurora B kinase and INCENP is thought to be responsible for H3 phosphorylation, chromosome condensation and the subsequent segregation of chromosomes. In this report, we show that chromosomes with DRT/DMC contain phosphorylated Chk1, consistent with activation of the S-M phase checkpoint. Furthermore, we show that INCENP is recruited to the DRT/DMC chromosomes during all phases of mitosis. In contrast, Aurora B kinase is absent on DRT/DMC chromosomes when these chromosomes lack serine 10 phosphorylation of H3. We also show that mitotic arrest deficient 2 (Mad2), a member of the spindle assembly checkpoint, is present on DRT/DMC chromosomes at a time when the normally condensed chromosomes show no Mad2 staining, indicating that DRT/DMC activates the spindle assembly checkpoint. Finally, cells with DRT/DMC chromosomes have centrosome amplification, abnormal spindle assembly, endoreduplication and significant chromosome instability.
Chang
B H
BH
Division of Pediatric Hematology and Oncology, Department of Pediatrics, Oregon Health & Science University, Portland, OR 97239, USA.
Smith
L
L
Huang
J
J
Thayer
M
M
D064107:Aurora Kinase B; D064127:Aurora Kinases; D002460:Cell Line; D018385:Centrosome; D043171:Chromosomal Instability; D002877:Chromosomes, Human; D004261:DNA Replication; D006801:Humans; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D008941:Spindle Apparatus
C576921:AURKB protein, human; D064107:Aurora Kinase B; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases