hPOC5 is a centrin-binding protein required for assembly of full-length centrioles

Abstract

Centrin has been shown to be involved in centrosome biogenesis in a variety of eukaryotes. In this study, we characterize hPOC5, a conserved centrin-binding protein that contains Sfi1p-like repeats. hPOC5 is localized, like centrin, in the distal portion of human centrioles. hPOC5 recruitment to procentrioles occurs during G2/M, a process that continues up to the full maturation of the centriole during the next cell cycle and is correlated with hyperphosphorylation of the protein. In the absence of hPOC5, RPE1 cells arrest in G1 phase, whereas HeLa cells show an extended S phase followed by cell death. We show that hPOC5 is not required for the initiation of procentriole assembly but is essential for building the distal half of centrioles. Interestingly, the hPOC5 family reveals an evolutionary divergence between vertebrates and organisms like Drosophila melanogaster or Caenorhabditis elegans, in which the loss of hPOC5 may correlate with the conspicuous differences in centriolar structure.

VDAC3 regulates centriole assembly by targeting Mps1 to centrosomes

“…S3A). This change in centriolar VDAC3 staining is consistent with the level of depletion we achieved, and there are several examples of centriolar proteins that are not completely depleted from centrioles by siRNA, including POC5, 29 …”

FOR20, a conserved centrosomal protein, is required for assembly of the transition zone and basal body docking at the cell surface

“…However, a role of this protein in the control of basal body elongation has not yet been documented. In this context, it will be interesting to test the interaction of PtCen2p with other proteins shown to control centriole length such as POC1, POC5 or OFD1 (Keller et al, 2009;Azimzadeh et al, 2009;Singla et al, 2010). PtCen2p depletion prevents the appearance of PtFOR20p in basal bodies, indicating that the former protein is required for the recruitment/stabilisation of the latter.…”

“…This distal localisation suggests that this protein could also be required for basal body docking at the cell surface. PtCen3p could thus be involved in different functions in association with diverse centrin-binding proteins, such as Sfi1 (Kilmartin, 2003) or hPOC5 (Azimzadeh et al, 2009) whose homologs exist in Paramecium (Gogendeau et al, 2007).…”

The Centrosome and Its Duplication Cycle

“…Cdc31 is a member of the centrin family of calmodulin-related proteins that are found at spindle poles of all eukaryotes (Salisbury 2007). Sfi1-related molecules with multiple centrin-binding motifs accompany centrins at human centrosomes; however, their function remains to be determined (Kilmartin 2003;Azimzadeh et al 2009). In budding yeast, the amino terminus of Sfi1 is anchored at the SPB, while the carboxyl terminus defines the end of the half-bridge extension.…”

“…Depletion of SPICE1 also results in short procentrioles, although, in contrast to its partners, overexpression of SPICE1 does not cause centriole elongation (Comartin et al 2013). The existence of a second mechanism controlling the length of the distal part of the centriole is suggested in HeLa cells where short procentrioles or centrioles with defective distal structures accumulate in the absence of POC5 (Azimzadeh et al 2009) and in Ofd1 mutants of mouse cells that display an abnormally elongated distal portion of centriole (Singla et al 2010).…”