Involved in nucleolar processing of pre-18S ribosomal RNA and ribosome assembly. Interacts with snoRNA U3. Interacts with MPP10, UTP21 and UTP25. Component of the ribosomal small subunit (SSU) processome composed of at least 40 protein subunits and snoRNA U3. Present with 9570 molecules/cell in log phase SD medium. Belongs to the WD repeat UTP18 family.