CEP295 interacts with microtubules and is required for centriole elongation

Abstract

Centriole duplication is a tightly ordered process during which procentrioles are assembled in G1-S and elongate during S and G2. Here, we show that human CEP295 (Drosophila Ana1) is not essential for initial cartwheel assembly, but is required to build distal half centrioles during S and G2. Using super-resolution and immunogold electron microscopy, we demonstrate that CEP295 is recruited to the proximal end of procentrioles in early S phase, when it is also localized at the centriolar microtubule wall that surrounds the human SAS6 cartwheel hub. Interestingly, depletion of CEP295 not only inhibits the recruitments of POC5 and POC1B to the distal half centrioles in G2, resulting in shorter centrioles, it also blocks the posttranslational modification of centriolar microtubules (e.g. acetylation and glutamylation). Importantly, our results indicate that CEP295 directly interacts with microtubules, and that excess CEP295 could induce the assembly of overly long centrioles. Furthermore, exogenous expression of the N-terminal domain of CEP295 exerts a dominantnegative effect on centriole elongation. Collectively, these findings suggest that CEP295 is essential for building the distal half centrioles and for post-translational modification of centriolar microtubules.

A novel atypical sperm centriole is functional during human fertilization

“…Similarly, Manandhar et al 5 found using immunogold labeling that CETN1/2 associates with microtubules at the point where the microtubules begin to splay in the DC, the same site where we observed the DC rods. This rod organization has never been described for any centriolar protein; most centriolar proteins and the structures within the distal lumen of a centriole exhibit radial symmetry in the form of disk and column structures 30–33 . Together, these findings demonstrate that several centrosomal proteins have an atypical distribution in the DC (Fig.…”

Cep295 is a conserved scaffold protein required for generation of a bona fide mother centriole

“…It will be interesting to investigate whether Cep295 molecules on the mother centriole are rearranged and moved to the assembly site of a procentriole to trigger centriole formation. It should also be noted that while this study was under review, another studies reported that Cep295 and Ana1 regulate centriole elongation in human42 and Drosophila cells43, respectively.…”

Once and only once: mechanisms of centriole duplication and their deregulation in disease

“…Centriole length can also be modulated by deregulation of proteins implicated in building the distal halves of centrioles, including the WD40 protein POC1 ( P roteome O f C entriole protein 1) 55 , the centrin-binding protein hPOC5 56 , or the microtubule binding protein CEP295 (Ana1 in Drosophila ) 57,58 . Interestingly, depletion of CEP295 not only impairs the recruitment of hPOC5 and POC1, but also blocks the acetylation and glutamylation of centriolar microtubules 57 . In vertebrates, these tubulin modifications accumulate on centrioles as well as cilia, and polyglutamylation is required for long-term stability of centriolar microtubules 59 .…”