Centrioles are 9-fold symmetrical structures at the core of centrosomes and base of
cilia whose dysfunction has been linked to a wide range of inherited diseases and
cancer [1]. Their duplication is regulated by a protein kinase of conserved structure,
the C. elegans ZYG-1 or its Polo-like kinase 4 (Plk4) counterpart in other organisms
[2-4]. Although Plk4's centriolar partners and mechanisms that regulate its stability
are known, its crucial substrates for centriole duplication have never been identified.
Here we show that Drosophila Plk4 phosphorylates four conserved serines in the STAN
motif of the core centriole protein Ana2 to enable it to bind and recruit its Sas6
partner. Ana2 and Sas6 normally load onto both mother and daughter centrioles immediately
after their disengagement toward the end of mitosis to seed procentriole formation.
Nonphosphorylatable Ana2 still localizes to the centriole but can no longer recruit
Sas6 and centriole duplication fails. Thus, following centriole disengagement, recruitment
of Ana2 and its phosphorylation by Plk4 are the earliest known events in centriole
duplication to recruit Sas6 and thereby establish the architecture of the new procentriole
engaged with its parent.
