Ribosome biogenesis factor that coordinates hyperactive transcription and ribogenesis (PubMed:17699751). Involved in nucleolar processing of pre-18S ribosomal RNA. Required for optimal pre-ribosomal RNA transcription by RNA polymerase I (PubMed:17699751). Essential for stem cell pluripotency and embryonic development. In the nucleoplasm, recruited by promoter-associated/nascent transcripts and transcription to active promoters where it facilitates releases of elongation factor P-TEFb and paused RNA polymerase II to allow transcription elongation and maintain high-level expression of its targets genes (By similarity). Interacts directly with UTP4 and UTP15 (PubMed:24219289). 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). Binds to RNA; binding is required for its chromatin association. Interacts with CDK9, DDX21 and SUPT6H. Interacts with RNA polymerase II (By similarity). Expressed during embryonic development, expression decreases at blastocyst stage. N-terminal domain is required for nucleoplasm location and C-terminal domain for nucleolus location. Belongs to the UTP5 family. Extended N-terminus.