STIL microcephaly mutations interfere with APC/C-mediated degradation and cause centriole amplification.
BACKGROUND
STIL is a centriole duplication factor that localizes to the procentriolar cartwheel region, and mutations in STIL are associated with autosomal recessive primary microcephaly (MCPH). Excess STIL triggers centriole amplification, raising the question of how STIL levels are regulated.


RESULTS
Using fluorescence time-lapse imaging, we identified a two-step process that culminates in the elimination of STIL at the end of mitosis. First, at nuclear envelope breakdown, Cdk1 triggers the translocation of STIL from centrosomes to the cytoplasm. Subsequently, the cytoplasmic bulk of STIL is degraded via the anaphase-promoting complex/cyclosome (APC/C)-proteasome pathway. We identify a C-terminal KEN box as critical for STIL degradation. Remarkably, this KEN box is deleted in MCPH mutants of STIL, rendering STIL resistant to proteasomal degradation and causing centriole amplification.


CONCLUSIONS
Our results reveal a role for Cdk1 in STIL dissociation from centrosomes during early mitosis, with implications for the timing of cartwheel disassembly. Additionally, we propose that centriole amplification triggered by STIL stabilization is the underlying cause of microcephaly in human patients with corresponding STIL mutations.
Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland.
Christian
C
Arquint
Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland. Electronic address: erich.nigg@unibas.ch.
Erich A
EA
Nigg
D000595:Amino Acid Sequence; D064173:Anaphase-Promoting Complex-Cyclosome / Q000378:metabolism; D016203:CDC2 Protein Kinase / Q000235:genetics / Q000378:metabolism; D002502:Centrioles / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008831:Microcephaly / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism
D047908:Intracellular Signaling Peptides and Proteins; C071236:STIL protein, human; D064173:Anaphase-Promoting Complex-Cyclosome; D016203:CDC2 Protein Kinase; D046988:Proteasome Endopeptidase Complex