YAP1 (Yes1 associated transcriptional regulator) is a Hippo pathway effector and transcriptional coactivator with diverse roles in development and disease. YAP1 functions as a transcription coregulator that interacts with TEAD family proteins and other transcriptional partners 1. In normal physiology, YAP1 regulates thrombopoiesis by binding myosin heavy chain 9 to promote megakaryocyte maturation and cytoskeletal activation 2, and controls granulosa cell function through mitochondrial regulation 3. Mechanistically, YAP1 nuclear translocation is suppressed by PIPKIγi5-mediated PI4,5P2 signaling, which promotes YAP1 binding to 14-3-3 proteins for cytoplasmic retention 4. CIC transcription factor directly represses YAP1 expression through GGAAGGAA DNA-binding motifs 5. In cancer, YAP1 promotes progression across multiple malignancies. YAP1 enhances NSCLC radioresistance by inducing epithelial-mesenchymal transition 6, drives bladder cancer through IL-6/STAT3 pathway activation and immunosuppressive myeloid cell expansion 7, and cooperates with β-catenin in hepatoblastoma tumorigenesis 1. YAP1 expression defines a distinct small cell lung cancer subtype 8. Clinically, YAP1 dysregulation associates with coloboma and developmental syndromes, while YAP1 inhibition represents a therapeutic strategy in multiple cancer contexts.