Asterless is a Polo-like kinase 4 substrate that both activates and inhibits kinase activity depending on its phosphorylation state.

Boese CJ, Nye J, Buster DW, et al. "Asterless is a Polo-like kinase 4 substrate that both activates and inhibits kinase activity depending on its phosphorylation state." Mol. Biol. Cell. 2018;29(23):2874-2886.