This indicates that CD8+ T cells need to override multiple checkpoints, including the requirements for activation signals for antigen presenting cells (APCs) and CD4+ T helper cells as well as bypassing regulatory T cell (Treg) suppression and molecular negative T cell regulators, in order to become pathogenic effectors [1], [2].
Checkpoint adaptation is the ability of a cell to override G2/M checkpoint arrest and proceed through the cell cycle even in the presence of unrepaired DNA damage, and it has been suggested that this is a mechanism by which cells might survive, even when damage persists (Galgoczy and Toczyski 2001).
It is not yet clear, however, why cells with the K250R mutant override the checkpoint: is it simply because unacetylated BubR1 is unstable or that it might also be deficient in inhibiting Cdc20?
Together, these results suggest that E-caddCR4h overrides this checkpoint.
In contrast, overriding the checkpoint interferes with correct nuclear segregation and results in an accumulation of binucleate mother cells [ 18, 22].
While incubation with a CHK1 inhibitor (UCN-01) overrode the checkpoint and triggered precocious mitotic entry as expected, depletion of SIK3 did not affect the cell cycle arrest.
They found that overexpression of AURKA and AURKB disruption overrides spindle checkpoint, resulting in the aneuploidy or polyploidy that occurs during cell division.
In particular, SYK-specific siRNA as well as SYK inhibitor PCT were effective in overriding a checkpoint-dependent mitotic arrest provoked by NOC treatment in both B-lineage lymphoid and non-lymphohematopoietic human cells.
Consistent with the ability to override cell cycle checkpoints, it has been observed that genomic instability is increased by latent EBV [29], and is probably attributable in part to the ability of EBNA3C to override a mitotic spindle checkpoint [30].
As a control for checkpoint override, we used reversine, a bona fide ATP-competitive inhibitor of the spindle checkpoint kinase Mps1 (Santaguida et al, 2010).
