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Open Biol. 2015 Nov;5(11). pii: 150160. doi: 10.1098/rsob.150160.

The RZZ complex requires the N-terminus of KNL1 to mediate optimal Mad1 kinetochore localization in human cells.

Author information

1
Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA.
2
Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO 80523, USA.
3
Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
4
Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA dileep.varma@northwestern.edu.
5
Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA jdeluca@colostate.edu.

Abstract

The spindle assembly checkpoint is a surveillance mechanism that blocks anaphase onset until all chromosomes are properly attached to microtubules of the mitotic spindle. Checkpoint activity requires kinetochore localization of Mad1/Mad2 to inhibit activation of the anaphase promoting complex/cyclosome in the presence of unattached kinetochores. In budding yeast and Caenorhabditis elegans, Bub1, recruited to kinetochores through KNL1, recruits Mad1/Mad2 by direct linkage with Mad1. However, in human cells it is not yet established which kinetochore protein(s) function as the Mad1/Mad2 receptor. Both Bub1 and the RZZ complex have been implicated in Mad1/Mad2 kinetochore recruitment; however, their specific roles remain unclear. Here, we investigate the contributions of Bub1, RZZ and KNL1 to Mad1/Mad2 kinetochore recruitment. We find that the RZZ complex localizes to the N-terminus of KNL1, downstream of Bub1, to mediate robust Mad1/Mad2 kinetochore localization. Our data also point to the existence of a KNL1-, Bub1-independent mechanism for RZZ and Mad1/Mad2 kinetochore recruitment. Based on our results, we propose that in humans, the primary mediator for Mad1/Mad2 kinetochore localization is the RZZ complex.

KEYWORDS:

Bub1; KNL1; Mad1; RZZ complex; kinetochore; spindle checkpoint

PMID:
26581576
PMCID:
PMC4680571
DOI:
10.1098/rsob.150160
[Indexed for MEDLINE]
Free PMC Article

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