Autophagy modulates the stability of Wee1 and cell cycle G2/M transition

The mammalian cell cycle is divided into four sequential phases, namely G1 (Gap 1), S (synthesis), G2 (Gap 2), and M (mitosis). Wee1, whose turnover is tightly and finely regulated, is a well-known kinase serving as a gatekeeper for the G2/M transition. However, the mechanism underlying the turnover of Wee1 is not fully understood. Autophagy, a highly conserved cellular process, maintains cellular homeostasis by eliminating intracellular aggregations, damaged organelles, and individual proteins. In the present study, we found autophagy deficiency in mouse liver caused G2/M arrest in two mouse models, namely Fip200 and Atg7 liver-specific knockout mice. To uncover the link between autophagy deficiency and G2/M transition, we combined transcriptomic and proteomic analysis for liver samples from control and Atg7 liver-specific knockout mice. The data suggest that the inhibition of autophagy increases the protein level of Wee1 without any alteration of its mRNA abundance. Serum starvation, an autophagy stimulus, downregulates the protein level of Wee1 in vitro. In addition, the half-life of Wee1 is extended by the addition of chloroquine, an autophagy inhibitor. LC3, a central autophagic protein functioning in autophagy substrate selection and autophagosome biogenesis, interacts with Wee1 as assessed by co-immunoprecipitation assay. Furthermore, overexpression of Wee1 leads to G2/M arrest both in vitro and in vivo. Collectively, our data indicate that autophagy could degrade Wee1—a gatekeeper of the G2/M transition, whereas the inhibition of autophagy leads to the accumulation of Wee1 and causes G2/M arrest in mouse liver.