Self-organization of Plk4 regulates symmetry breaking in centriole duplication

Abstract

During centriole duplication, a single daughter centriole is formed next to the mother centriole. The molecular mechanism that determines a single duplication site remains a long-standing question. Here, we show that intrinsic self-organization of Plk4 is implicated in symmetry breaking in the process of centriole duplication. We demonstrate that Plk4 has an ability to phase-separate into condensates via an intrinsically disordered linker and that the condensation properties of Plk4 are regulated by autophosphorylation. Consistently, the dissociation dynamics of centriolar Plk4 are controlled by autophosphorylation. We further found that autophosphorylated Plk4 is already distributed as a single focus around the mother centriole before the initiation of procentriole formation, and is subsequently targeted for STIL-HsSAS6 loading. Perturbation of Plk4 self-organization affects the asymmetry of centriolar Plk4 distribution and proper centriole duplication. Overall, we propose that the spatial pattern formation of Plk4 is a determinant of a single duplication site per mother centriole.

A Theory of Centriole Duplication Based on Self-Organized Spatial Pattern Formation

“…We then investigated how the discrete ring patterns of Plk4, with six uneven foci, are generated from the 12 slots of CEP152. To address this, we reasoned that the molecular nature of Plk4, which has recently been revealed (Yamamoto and Kitagawa, 2018), may provide a clue. Firstly, Plk4 self-assembles into a macromolecular complex (or protein aggregate).…”

“…Accordingly, here we propose the first verifiable theory explaining the mechanism by which the self-organization properties of Plk4 form dynamic spatial patterns and exclusively provide the single duplication site during centriole duplication. The core concept of this theory, which is based on a recently proposed speculative model (Yamamoto and Kitagawa, 2018), is shown in Figure 4.…”

“…This promotes the dissociation of activated Plk4, generating the lateral inhibition effect. Importantly, when the total amount of Plk4 in a segment reaches a given threshold, the molecules are assumed to form a stable complex (aggregate) (Yamamoto and Kitagawa, 2018), which reduces the dissociation rates of both forms of Plk4. A random fluctuation (±10%) was added to the self-assembly term, so the results differ in each simulation.…”

“…A recent study investigating the molecular dynamics of Plk4 revealed that it possesses intrinsic self-organization properties, such as self-assembly and the promotion of dissociation/degradation of neighboring Plk4 molecules in an autophosphorylation-dependent manner (Yamamoto and Kitagawa, 2018). This finding suggests that: 1) Plk4 itself may generate the bias in the spatial patterns around centrioles, and 2) subsequent loading of STIL and HsSAS6 may reinforce this bias to cooperatively provide the single duplication site.…”

“…Simulations using appropriate mathematical models rather than qualitative reasoning may reproduce and even predict experimental data, enabling verification of the theory. Based on previous findings related to the self-organizing properties of Plk4 (Yamamoto and Kitagawa, 2018), we here propose the first theory of centriole duplication mechanisms by integrating experimental data and mathematical modeling.…”