The activator PntP2 and repressors Yan and Ttk88 are regulated by EGFR signaling, and Ttk88 also responds to Sev and Notch signaling. In addition, Notch positively regulates sev expression and negatively regulates svp, which encodes a repressor of pros. The eye-specific transcription factors Gl, Eya/So, and Lz also contribute to pros activation. lz is itself a target of Gl, Eya and So. This diagram only indicates the factors that bind to the Pros enhancer, and not the correct number or placement of their binding sites.