RRP1B (ribosomal RNA processing 1B) is a transcriptional coactivator located on chromosome 21 with primary roles in both viral response and cancer biology. Following influenza A virus infection, RRP1B promotes viral mRNA transcription by facilitating binding of IAV RNA-directed RNA polymerase to capped mRNA [UniProt]. Beyond viral functions, RRP1B regulates alternative splicing and gene expression through physical and functional interactions with splicing regulators like SRSF1, thereby modulating expression of over 600 genes involved in cell cycle regulation 1. RRP1B has emerged as a novel susceptibility gene for breast cancer progression and metastasis 2. Germline polymorphisms in RRP1B (particularly 1307T>C) are significantly associated with increased breast cancer risk, with the T allele conferring 1.75-fold elevated risk and correlating with advanced disease, positive lymph node status, and poor survival 34. RRP1B interacts functionally with metastasis modifier SIPA1 to suppress tumor growth and modulate extracellular matrix gene expression 2. Beyond breast cancer, RRP1B shows clinical relevance as a diagnostic biomarker. Its expression is significantly elevated in early gastric cancer tissues and plasma, correlating with distal metastasis and tumor-node-metastasis staging 5. RRP1B also functions as a sepsis biomarker with diagnostic AUC >0.95 and participates in lymphocyte activation and differentiation 6. Recent GWAS identified RRP1B variants associated with serum lipid levels through gene-by-psychosocial interactions, suggesting potential drug repurposing opportunities with Atenolol 7.