Individual Src-family tyrosine kinases direct the degradation or protection of the clock protein Timeless via differential ubiquitylation

► The clock protein Timeless is essential for circadian cycle regulation in Drosophila ► Timeless also governs cell cycle control and embryonic development in mammals ► Phosphorylation of Timeless by Src-family kinases induces ubiquitylation ► Stabilization of Timeless by c-Src results from K63-linked ubiquitylation ► Src family members may work in concert to coordinate Timeless function