Chromosomes with delayed replication timing lead to checkpoint activation, delayed recruitment of Aurora B and chromosome instability

Abstract

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.

Karyotypic Instability and Centrosome Aberrations in the Progeny of Finite Life-Span Human Mammary Epithelial Cells Exposed to Sparsely or Densely Ionizing Radiation

“…Cells with DRT/DMC activate the S/M cell cycle checkpoint with delayed recruitment of Aurora B along with abnormal centrosome amplification leading to chromosome instability (59). This phenotype has been observed in normal human lymphocytes, in mouse kidney epithelium and mouse ear fibroblasts after radiation exposure.…”

When 2+2=5: The origins and fates of aneuploid and tetraploid cells

“…Both initiation and completion of DNA replication were delayed, by 2–3 hours, with DMC chromosomes continuing to replicate DNA into mitosis [73]. Delayed replication occurred across the entire chromosome, suggesting that the presence of the translocation somehow globally disrupts timing of replication across the chromosome, but in a chromosome-autonomous fashion.…”

Abnormal developmental control of replication-timing domains in pediatric acute lymphoblastic leukemia

“…Several studies have identified abnormal temporal control of replication in many cancers (Amiel et al 2001Smith et al 2001;Sun et al 2001;KorensteinIlan et al 2002). For example, specific chromosome translocations result in a chromosome-wide delay in replication timing (Breger et al 2005;Chang et al 2007) that is found frequently in cancer cells (Smith et al 2001). Some cancer-specific replication-timing changes appear to be epigenetic in that, similar to developmental changes, they are mitotically stable but do not involve detectable genetic lesions (Eul et al 1988;Adolph et al 1992).…”