Processing of Precursor 4 (POP4) is a member of the eukaryotic/archaeal RNase P protein component 1 family. POP4 is one of the protein subunits of the small nucleolar ribonucleoprotein complexes: the endoribonuclease for mitochondrial RNA processing complex and the ribonuclease P complex. POP4 is confined to the nucleus and associates promptly with the RNA component of this complexes.POP4 is participating in processing of precursor RNAs.