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. Interacts with UTP4. Interacts with FBL/fibrillarin in a transcription-dependent manner (PubMed:22916032). May associate with the proposed t-UTP subcomplex of the SSU processome containing at least UTP4, WDR43, HEATR1, UTP15, WDR75. Is the likely candidate for being the functional analog of yeast Utp8. May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. Wrong choice of frame.