Unicellular S. cerevisiae (Saccharomyces cerevisiae) undergoes developmental switches between two differentiation states in response to environmental cues. Under stress conditions, diploid S. cerevisiae cells switch from the yeast form (growth as single oval cells) to the filamentous or pseudohyphae form (growth as elongated cell chains that retain physical attachment between the mother and daughter cells). Filamentous differentiation of S. cerevisiae is a potential model system for study of eukaryotic differentiation. Slowed DNA synthesis induces filamentous differentiation in yeast and it involves the conserved cell cycle regulators Swe1 (Mitosis Inhibitor Protein Kinase-Swe1), Clb2 and CDC28 (Cell Division Control Protein-28) (Ref.1). DNA integrity checkpoints are conserved signaling pathways that are activated by DNA damage or replication blocks to delay cell cycle progression [...]