Ribosome biogenesis factor that coordinates hyperactive transcription and ribogenesis (PubMed:31128943). Involved in nucleolar processing of pre-18S ribosomal RNA. Required for optimal pre-ribosomal RNA transcription by RNA polymerase I (By similarity). Essential for stem cell pluripotency and embryonic development (PubMed:31128943). 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 (PubMed:31128943). Interacts with UTP4 and UTP15. 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. Binds to RNA; binding is required for its chromatin association (PubMed:31128943). Interacts with CDK9, DDX21 and SUPT6H (PubMed:31128943). Interacts with RNA polymerase II (PubMed:31128943). Detected at low levels at least in heart, liver, lung, spleen, thymus and hippocampus. Expressed during embryonic development, expression decreases at morula stage. N-terminal domain is required for nucleoplasm location and C-terminal domain for nucleolus location. Belongs to the UTP5 family.