UTP4 (also known as CIRH1A or TEX292) is a nucleolar protein component of the t-UTP subcomplex within the small subunit (SSU) processome, a ribonucleoprotein complex essential for ribosomal biogenesis. Its primary function is facilitating maturation of 18S rRNA and small ribosomal subunit assembly 1. The protein operates through protein-protein interactions, particularly with Utp8, which are critical for SSU processome assembly and ribosomal RNA processing 1. UTP4 is subject to arginine methylation, a modification associated with RNA processing and ribonucleoprotein complex biogenesis 2. Disruption of UTP4 function has significant disease implications. Missense mutations in UTP4/CIRH1A cause North American Indian Childhood Cirrhosis (NAIC), an autosomal recessive cholestatic disease 3. NAIC pathogenesis involves p53-mediated cellular stress response triggered by defective ribosome biogenesis, leading to biliary development defects 3. Additionally, elevated UTP4 expression correlates with colorectal cancer proliferation, suggesting extraribosomal oncogenic functions 4. Clinically, UTP4 represents both a genetic risk factor for developmental disease and a potential cancer therapeutic target. Its role as a nucleolar stress sensor linking ribosomal dysfunction to cellular pathways underscores the importance of ribosomal proteins in human disease 3.