RNH1 (ribonuclease/angiogenin inhibitor 1) functions as a multifaceted regulator with primary roles in RNA protection and cellular homeostasis. The protein acts as a ribonuclease inhibitor that binds and inhibits several ribonucleases including RNASE1, RNASE2, and angiogenin (ANG) 1. Under normal conditions, RNH1 resides in the cytoplasm where it protects cellular RNAs from degradation and inhibits ANG's cytotoxic tRNA ribonuclease activity 1. During cellular stress, RNH1 undergoes nuclear translocation, relieving its inhibition of ANG in the cytoplasm while simultaneously inhibiting ANG's angiogenic activity in the nucleus 1. Beyond RNA regulation, RNH1 demonstrates significant roles in immune modulation and cancer biology. The protein dampens inflammasome activation by decreasing pro-IL-1β expression and promoting proteasome-mediated caspase-1 degradation, with RNH1 levels negatively correlating with COVID-19 disease severity 2. In cancer contexts, RNH1 exhibits tumor suppressive functions, with low expression associated with enhanced invasion and metastasis in bladder cancer 3 and promoting angiogenesis when deficient in prostate cancer 4. Additionally, RNH1 can stabilize mRNAs through interactions with other RNA-binding proteins, contributing to metabolic regulation 5.