Ribosome biogenesis factor. Involved in nucleolar processing of pre-18S ribosomal RNA. Required for optimal pre-ribosomal RNA transcription by RNA polymerase I. May be a component of the proposed t-UTP subcomplex of the ribosomal small subunit (SSU) processome containing at least UTP4, WDR43, HEATR1, UTP15, WDR75 (PubMed:17699751, PubMed:22916032).