Endoribonuclease which preferentially cleaves ApU and ApG phosphodiester bonds. Hydrolyzes UpU bonds at a lower rate (PubMed:17881363). Regulates the activity of vacuolar (H+)-ATPase (V- ATPase) which is responsible for acidifying and maintaining the pH of intracellular compartments (PubMed:26212330). Required at an early stage of receptor-mediated endocytosis (PubMed:26212330). . (Microbial infection) Required at an early stage of both clathrin-mediated and clathrin-independent endocytic uptake of a diverse set of viruses, including dengue, West Nile, Sindbis, Rift Valley Fever, influenza, and human rhinoviruses (PubMed:26056282, PubMed:26212330). {ECO:0000269|PubMed:26056282, ECO:0000269|PubMed:26212330}. This is the function of RNASEK (ribonuclease K, ENSG00000219200).