HEATR1 (HEAT repeat containing 1) is a nucleolar ribosome biogenesis factor essential for small subunit (SSU) processome assembly and pre-ribosomal RNA processing 1. As a component of the SSU processome, HEATR1 facilitates recruitment of ribosomal proteins and RNA chaperones to nascent pre-rRNA, promoting RNA folding, modifications, and coordinated cleavage by the RNA exosome 1. HEATR1 directly regulates ribosomal DNA binding and associates with RNA polymerase I transcription/processing factors to optimize pre-rRNA synthesis 2. Additionally, HEATR1 recruits MYC to nucleoli and is required for MYC-driven ribogenesis 1. Clinically, HEATR1 dysregulation is implicated in multiple cancers. In hepatocellular carcinoma, HEATR1 is upregulated by mTORC1 signaling and promotes tumor growth by dominating ribosome biogenesis and proteome homeostasis; high HEATR1 expression correlates with poor survival 2. In contrast, HEATR1 deficiency in pancreatic cancer promotes proliferation and gemcitabine resistance through Nrf2 pathway activation, with low HEATR1 associated with poor prognosis 3. HEATR1 functions as a negative AKT regulator in pancreatic cancer, sensitizing cells to chemotherapy; downregulation associates with treatment resistance and shorter overall survival 4. In gastric and oral squamous cell carcinomas, HEATR1 promotes proliferation via mTOR activation and Pontin/Reptin stabilization 5 6. Multiomics analysis links HEATR1 to cardiac structure and function regulation 7.