Building a centriole

Abstract

Centrioles are the key foundation of centrosomes and cilia, yet a molecular understanding of how they form has only recently begun to emerge. Building a fully functional centriole that can form a centrosome and cilium requires two cell cycles. Centriole building starts with procentriole nucleation, a process that is coordinated by the conserved proteins Plk4/Zyg-1, and Asterless/Cep152. Subsequently, Sas-6, a conserved procentriole protein, self-assembles to provide nine-fold symmetry to the centriole scaffold. The procentriole then continues to elongate into a centriole, a process controlled by Sas-4/CPAP and CP110. Then, centrioles recruit Sas-4-mediated pre-assembled centrosomal complexes from the cytoplasm to form the pericentriolar material (PCM). Finally, CP110 and its interacting proteins are involved in controlling the timing of centriole templating of the cilium.

Fig 1. Building of a centriole

Depiction of the structural and molecular events taking place during the formation of one of the centrioles in a cell (depicted in blue) through two consecutive cell cycles. During the first cell cycle (light gray background, A–E), the basic structure of the centriole is formed. During second cell cycle (darker gray background, F–I), the immature centriole acquires functions in a step-by-step manner until it become fully mature and functional (H). A second centriole formed near the original centriole is depicted in light brown. Major events in the formation of the centriole are noted in blue. Key proteins are indicated in orange. Centrioles are depicted as they would appear from a cross section (B) and a side view (C–I).