KDM4A serves as an α-tubulin demethylase regulating microtubule polymerization and cell mitosis.

Posttranslational modifications of tubulin give microtubule distinct properties to support diverse cellular functions. Trimethylation on lysine-40 of α-tubulin (α-TubK40me3) is involved in cell division and neuronal development. The "writer" (SETD2) and "reader" (PBRM1) of α-TubK40me3 have been identified. However, the "eraser" of α-TubK40me3 and the impact of α-TubK40me3 dynamic balance on cells are still unclear. Here, we report that KDM4A, a member of the histone demethylase family, binds α-tubulin through its catalytic core domain and demethylates α-tubulin. KDM4A knockout significantly enhances α-TubK40me3, inducing microtubule polymerization and mitotic defects. Furthermore, the overpolymerized microtubules and cell mitotic defects caused by KDM4A knockout are rescued by reducing α-TubK40me3 with overexpression of an α-tubulin mutant α-tubulin(K40A) or depolymerizing microtubules with nocodazole treatment in cells. Together, our study identifies KDM4A as an α-tubulin demethylase, and this demethylation is important for regulating microtubule polymerization and cell mitosis.