Ribosome biogenesis factor. May be required for both optimal rDNA transcription and small subunit (SSU) pre-rRNA processing at sites A', A0, 1 and 2b (By similarity). Interacts with UTP4. Interacts with FBL/fibrillarin in a transcription-dependent manner. May associate with the proposed t-UTP subcomplex of the SSU processome containing at least UTP4, WDR43, HEATR1, UTP15, WDR75.