Kinetic analysis of de novo centriole assembly in heat-shocked mammalian cells

Mammalian cells are capable of de novo centriole formation after the removal of existing centrioles. This suggests that de novo centriole assembly is repressed in normally duplicating cells to maintain a constant number of centrioles in the cells. However, neither the mechanism of de novo centriole assembly nor that of its hypothesized repression is understood due to the lack of an experimental system. We found that the heat shock (HS; 42°C, 2 h) of mouse embryonic fibroblasts caused the separation of centriole pairs, a transient increase in polo-like kinase (Plk) 4 expression, and the formation of a complex containing γ-tubulin, pericentrin, HS protein (Hsp) 90, and Plk4, in approximately half of the cells. Subsequently, spindle-assembly abnormal protein (Sas) 6, centrosomal protein (Cep) 135, and centrin localized to the complex, and tubulin consequently became polyglutamylated, indicating de novo centriole assembly in the heat-shocked cells. These results suggested that HS-induced de novo centriole assembly could provide an experimental system for further elucidating the regulation of centrosome number in mammalian cells.