GPATCH4 is a nucleolar G-patch domain protein that functions as a critical regulator of ribosome biogenesis and RNA modification 1. As a stimulatory cofactor of the RNA helicase DHX15, GPATCH4 regulates 2'-O-methylation of ribosomal and small nuclear RNAs through both DHX15-dependent and independent mechanisms, essential for efficient protein synthesis 1. GPATCH4 also interacts with the helicase DDX21 to regulate nucleolar R-loops and rRNA transcription 2. Beyond its role in RNA processing, GPATCH4 maintains nucleolar architecture and morphology; its depletion decreases fibrillar centers and dense fibrillar components while impairing cell viability and promoting apoptosis and cellular senescence 134. GPATCH4 serves as a binding partner for the long noncoding RNA CUL1-IPA in maintaining nucleolar integrity 5. Clinically, GPATCH4 is amplified in >70% of hepatocellular carcinoma patients, with high expression predicting poor prognosis and promoting HCC cell proliferation through enhanced rRNA transcription 2. Additionally, GPATCH4 has been identified as a targeted gene of contraindicated medications in migraine pathogenesis 6. Overall, GPATCH4 is a multifunctional nucleolar protein essential for ribosome formation, RNA modification, and cellular proliferation with emerging roles in cancer biology.