Chk1 is the primary checkpoint protein against which many small molecule inhibitors have been developed [ 1- 3].
While comprehensive proof of senescence-induced senescence in tissues awaits the analysis of a senescence reporter system in vivo, our data already indicate that senescent cells induce a bystander effect that spreads DNA damage and, ultimately, induces cell senescence in primary, checkpoint-competent cells in vitro and, possibly, in vivo.
At airports, passengers go through the primary screening checkpoint, and some are selected for secondary screening, which includes a baggage search and some kind of body search, like a pat-down.
When a cell is challenged, the balance between the proapoptotic and antiapoptotic Bcl-2 family members such as Bcl-xL serves as a primary control checkpoint regulating cell death and survival.
Checkpoint kinase-1 is thought to be the primary S-phase checkpoint kinase, with Chk2 playing a supportive role.
Petitioners propose several ways in which the narcotics-detection purpose of the instant checkpoint program may instead resemble the primary purposes of the checkpoints in [Michigan v.] Sitz (1990) and [United States v.] Martinez-Fuerte (1976).
The security agency was required by federal law to seek public comment before using the scanners for primary screening at airport checkpoints.
Both MRC5 and U2OS cell lines were subsequently used in parallel for most experiments to ascertain if any observed effects required the more reliable cell cycle checkpoints of primary cells (MRC5) and thus were not recapitulated in transformed cell lines such as the U2OS line that has stable p53- and pRb-dependent checkpoints but is defective for p16INK [24], [24].
In contrast to primary cells with intact checkpoints, the induction of replication stress in response to CIN was shown to aggravate the CIN-phenotype in checkpoint-deficient, human cancer cells (Burrell et al., 2013).
Hence, a partial depletion of HP1α would affect cohesin protection and result in a prolonged prometaphase in primary cells due to checkpoint activity.
