In yeast and humans, BUBR1, BUB3 and MAD2 may be found together in large complexes (mitotic checkpoint complex) [7], [17], [19].
Alternatively, working out the role of the Ndc80 complex in checkpoint control is challenging: for instance, only when levels of hNDC80 complex subunits were depleted below ∼1% of wild-type level was the human spindle checkpoint inactivated [56].
The effect of Mrc1 is more similar to that of the MRX complex, another checkpoint complex with roles in telomere capping [36,42,54,55].
Cohesin proteins contain SMC1 and SMC3, while SMC5 and SMC6 (along with several non-SMC components) are part of a DNA repair complex with checkpoint function [ 70, 71].
APC is also involved in chromosomal segregation, whereby it localizes to the ends of microtubules within the kinetochore and forms a complex with checkpoint proteins [ 35, 44].
Consistent with a functional crosstalk between the Ddc2– Mec1 and 9 1 1 complexes during checkpoint signaling, there is a reported requirement for the 9 1 1 complex to stabilize Ddc2 foci in irradiated G1 cells (Barlow et al. 2008).
A second level of regulation allows adjustment of the expression of the particular catabolic operons in response to the global environmental conditions of the cells, and recent findings provide some clues about the mechanisms underlying such complex regulatory checkpoints.
In Figure 2C we compared wild-type, mph1Δ, and mph1-kd strains for their ability to form MCC-APC/C complexes and checkpoint arrest.
BRCT repeats have been also described as phosphopeptide-interacting motifs, facilitating the assembly of DNA damage signaling complexes following checkpoint kinases activation [ 9].
ME detects the same complexes as SCE, and additionally the mitotic checkpoint complex.
