Processing Of Precursors 1 (POP1)

POP1 is a protein subunit of two different small nucleolar ribonucleoprotein complexes: the endoribonuclease for mitochondrial RNA processing complex and the ribonuclease P complex. This protein is a ribonuclease that localizes to the nucleus and functions in pre-RNA processing.Human POP1 encodes a predicted 1,024-amino acid protein that has a pI of 9.86. On Northern blots, human POP1 is expressed as a major 4.1-kb and minor 6-kb transcript, perhaps due to alternative polyadenylation signals. Anti-POP1 antibodies recognize a doublet of approximately 115 kD on Western blots. In HeLa cells, human POP1 localizes to the nucleus and strongly accumulates in the nucleolus. In co-immunoprecipitation studies, POP1 was associated with both RNase P and RNase MRP snRNAs, and with RNase P enzymatic activity.