The DNA damage response (DDR)?a central axis in the maintenance of genomic stability-has emerged as a complex signaling network that affects many aspects of cellular metabolism. A major arm of the DDR activates special checkpoints that temporarily arrest cell cycle progression while damage is being assessed and processed. Many DDR arms are driven by several parallel pathways acting in concert. Such is the case with the damage-induced G1/S checkpoint. A new pathway driving this checkpoint draws attention to the complexity of the DDR, which allows tight but fine-tuned control of the cellular response to threats to genomic integrity.