Required for small ribosomal subunit (SSU) synthesis. Has a role in the processing of early nucleolar and late cytoplasmic pre-RNA species. Recruits DIM1 to nucleolar pre-RNAs. Indirectly required for cleavage at the A2 site of the 20S pre-rRNA, forming 18S rRNA, and at A1 and A2 sites of other pre-rRNAs. Component of the small ribosomal subunit, ribosomal RNA processing complex (SSU RRP complex). Interacts with NOB1. Belongs to the PNO1 family.