URB1 (URB1 ribosome biogenesis factor) is an essential ribosome assembly factor that plays a critical role in ribosome biogenesis and cellular growth regulation 1. The protein functions downstream of the mTORC1 signaling pathway, where RAPTOR promotes URB1 expression to regulate ribosome assembly and protein synthesis 21. URB1 is required for proper synthesis of ribosomal subunits and polysome assembly, with disruptions leading to impaired cell proliferation and developmental defects in digestive organs 1. In cancer contexts, URB1 is overexpressed in colorectal cancer and contributes to tumorigenesis through transcriptional activation of ATF4 via XBP1-mediated mechanisms, promoting cell cycle progression and proliferation 3. The protein's expression correlates with clinicopathological characteristics and serves as a prognostic indicator in colorectal cancer 23. Additionally, URB1 mutations have been associated with survival outcomes in metastatic renal cell carcinoma patients receiving targeted therapy 4. The gene's antisense RNA (URB1-AS1) has been implicated in various cancers, including hepatocellular carcinoma and pituitary adenomas, suggesting broader regulatory roles beyond the primary ribosome biogenesis function 56.