Involved in nucleolar processing of pre-18S ribosomal RNA. Required for optimal pre-ribosomal RNA transcription by RNA polymerase I together with a subset of U3 proteins required for transcription (t-UTPs). Involved in ribosome biosynthesis. Interacts with snoRNA U3. Interacts with MPP10. Component of the ribosomal small subunit (SSU) processome composed of at least 40 protein subunits and snoRNA U3. In the absence of snoRNA3, forms a complex with other t-UTPs. This complex can associate with pre-18S ribosomal RNAs. Associated with ribosomal chromatin, even in the absence of transcription. Present with 18200 molecules/cell in log phase SD medium. Belongs to the HEATR1/UTP10 family.